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Dynamics of hummingbird mediated pollen flow in a subalpine meadow Perkins, Mary Dee Chynoweth 1978

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DYNAMICS OF HOMHINGBIBD MEDIATED POLLEN FLOW IN A STJBALPINE MEADOW By MARY DEE CHYNOWETH PERKINS B.Sc., U n i v e r s i t y of Oklahoma, 1973 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n THE FACULTY OF GRADUATE STUDIES (Department of Zoology) We accept t h i s t h e s i s as conforming to the r e q u i r e d standard THE UNIVERSITY OF BRITISH COLUMBIA December, 1977 (c)Mary Dee Chynoweth P e r k i n s , 1977 In presenting th i s thes is in pa r t i a l fu l f i lment of the requirements for an advanced degree at the Un ivers i ty of B r i t i s h Columbia, I agree that the L ibrary sha l l make it f ree ly ava i l ab le for reference and study. I fur ther agree that permission for extensive copying of th i s thesis for scho lar ly purposes may be granted by the Head of my Department or by his representat ives. It is understood that copying or pub l i ca t ion of th is thes is for f inanc ia l gain sha l l not be allowed without my writ ten permission. Department of The Univers i ty of B r i t i s h Columbia 2075 Wesbrook P l a c e Vancouver, Canada V6T 1W5 Date 12 Jan. 1978 i A b s t r a c t P r e v i o u s authors have concluded that hummingbird t e r r i t o r i a l boundaries would r e s t r i c t p o l l e n flow. I questioned the v a l i d i t y of t h i s on the time s c a l e of a blooming season f o r a system i n which i n d i v i d u a l p l a n t s remained i n f l o w e r while the t e r r i t o r i e s surrounding them o f t e n changed i n s i z e and shape. To determine the e f f e c t s o f hummingbird f o r a g i n g behavior on p o l l e n flow, I s t u d i e d s i x components of a hummingbird-plant p o l l i n a t i o n system: hummingbird t e r r i t o r i a l behavior, p l a n t blooming time, f o r a g i n g f l i g h t d i s t a n c e s , p o l l e n c a r r y over, other p o l l i n a t o r s , and p l a n t breeding systems. Osing t h i s i n f o r m a t i o n I found I c o u l d d e p i c t p o l l e n flow between two p l a n t s as a f u n c t i o n o f : 1) The f l o w e r i n g times of the p l a n t s . 2) The d i s t a n c e between the p l a n t s . 3) The amount of time these p l a n t s are surrounded by the same t e r r i t o r i a l boundaries. 4) The number of p l a n t s (or flowers) the b i r d v i s i t s before v i s i t i n g the second p l a n t . I found t h a t the i n f l u e n c e of t e r r i t o r i a l boundaries on p o l l e n flow i s determined not by the boundary of a s i n g l e t e r r i t o r y , but by the i n f l u e n c e of a l l the t e r r i t o r i a l boundaries surrounding a p l a n t while i t i s i n bloom. Within these boundaries, the p r o b a b i l i t y o f p o l l e n being t r a n s f e r e d between two p l a n t s i s a f u n c t i o n of the amount of time they are w i t h i n the same boundary. The l e n g t h o f hummingbird f o r a g i n g f l i g h t s i s a l s o a major determinant of p o l l e n flow and the predominance of i i short flights between plants may restrict pollen flow probabilities. The restriction imposed by these short flights may be reduced by 1) long pollen carry over distances and 2) the longer flight distances between a perch and a plant. i i i T a b le Of Contents A b s t r a c t i LI ST OF FIGURES . . ... v i LIST OF TABLES ............................................ v i i i fiCKNOBLEDGEMENTS . . . . . . . . . . v . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i x INTRODUCTION 1 THE COMPONENTS OF A HUMMINGBIRD-MEDIATED POLLINATION SYSTEM 5 T e r r i t o r i a l Behavior and P l a n t Flowering Times 6 Foraging F l i g h t Distances .............................. 8 P o l l e n C a r r y Over 8 Other P o l l i n a t o r s 9 Plan t Breeding Systems 10 METHODS ...... , . . . .. .. 11 The Study Area 11 T e r r i t o r i a l Behavior ................................... 12 Foraging Behavior 15 P l a n t Flowering Times 17 P o l l e n Carry Over 17 Other P o l l i n a t o r s 18 P l a n t Breeding Systems 21 BESULTS 22 T e r r i t o r i a l B e h a v i o r . . . . . 22 P l a n t Flowering Time 22 Foraging Behavior 37 P o l l e n C a r r y Over 54 Other P o l l i n a t o r s ...................................... 55 Pla n t Breeding Systems 59 DISCUSSION 63 P o l l e n Flow 63 The E f f e c t Of F l i g h t s To And From A Perch .............. 76 P o l l e n C a r r y Over 78 I n s e c t P o l l i n a t o r s 81 Pla n t Density 83 Gene Flow ...... .................. .................... ... .. 84 I m p l i c a t i o n s For Other Hummingbird P o l l i n a t i o n Systems . 86 LITERATURE CITED APPENDIX LIST OF FIGURES Figu r e 1 : Photos And Drawings Of Columbine And Indian Paintbrush. .......................13 Figure 2 : Photo Of Fuchsia Hybrida 19 Fig u r e 3 : Changes In S i z e And Shape Of T e r r i t o r i e s In Meadow 1. 23 Fi g u r e 4 : Changes In S i z e And Shape Of T e r r i t o r i e s In Meadow 2. .25 Fig u r e 5 : Changes In T e r r i t o r y Numbers And S i z e ; Meadow 1. . ....... 27 Fig u r e 6 : Changes In T e r r i t o r y Numbers And S i z e ; Meadow 2. ... 29 Fi g u r e 7 : Flowering Stages In Columbine. .... .......31 F i g u r e 8 : Flowering Stages In Indian P a i n t b r u s h . .........33 Fi g u r e 9 : Mean F l i g h t Distance Between Patches Of Columbine. .............................................39 Figure 10 : Mean F l i g h t Distance Between Patches Of Indian Paintbrush. <41 Fi g u r e 11 : Freguency D i s t r i b u t i o n Of D i s t a n c e s Between S u c c e s s i v e l y V i s i t e d Columbine Patches. ................ 43 Fig u r e 12 : Freguency D i s t r i b u t i o n Of Distances Between S u c c e s s i v e l y V i s i t e d Indian Paintbrush Patches. ........45 Figu r e 13 : The Mean F l i g h t D i s t a n c e To And From Perches. .49 Fi g u r e 14 : R e l a t i o n s h i p Beween T e r r i t o r y S i z e And Two Cat e g o r i e s Of Hummingbird F l i g h t D i s t a n c e s . ............52 Fi g u r e 15 : P o l l e n Carry Over For Hummingbirds V i s i t i n g Fucshia Flowers 56 F i g u r e 16 : The E f f e c t s Of Changes I n T e r r i t o r i a l Boundaries On P o t e n t i a l P o l l e n Flow For fl P l a n t In Meadow 1. ...65 Fig u r e 17 : Diagramatic Representation Of P o l l e n Flow For Two Columbine P l a n t s In Meadow 1. 69 Fig u r e 18 : Diagramatic R e p r e s e n t a t i o n Of P o l l e n Flow For Two Indian Paintbrush P l a n t s In Meadow 2. ..............72 Figu r e 19 : Changes In The Number Of Columbine Flowers And Indian P a i n t b r u s h I n f l o r e s c e n c e s I n Meadow 1. ..........97 Fi g u r e 20 : Changes In Number Of Columbine Flowers In Meadow 2. .99 Fi g u r e 21 : Changes In The Number Of I n d i a n P a i n t b r u s h I n f l o r e s c e n c e s I n Meadow 2. ............................ 101 v i i i LIST OF TABLES Table I . Length Of Flowering Time For Columbine ...........35 Table I I . Length Of Flowering Time For Indian P a i n t b r u s h ..36 Table I I I . The I n f l u e n c e Of T e r r i t o r i a l Boundaries Cn Hummingbird Foraging ................................... 38 Tabl e IV. P r o b a b i l i t y Of P o l l e n Flow For Columbine And Indian P a i n t b r u s h 48 Table V. R e l a t i o n s h i p Between The Number Of Flowers i n A Patch To Those On A P l a n t .................51 Table VI. P r o b a b i l i t y Of P o l l e n Flow For Columbine And Indian P a i n t b r u s h Based On P o l l e n C a r r y Over To The Tenth Flower V i s i t e d .58 Table VII. Seed set Data For Columbine .........61 Table V I I I . Seed Set Data For Indian Paintbrush ...........62 Table IX. Times Of Insect V i s i t o r A c t i v i t y ................95 Table X. Number Of Patches, Flowers And I n f l o r e s c e n c e s (Indian Paintbrush) V i s i t e d In A F l i g h t ...96 ACKNOWLEDGEMENTS "The journey need not be alone at a l l moments. We can and do spark one another, and c a r r y each other on." Paulus Berensohn My a d v i s o r Lee Gass i n t r o d u c e d me to G r i z z l y Lake and i t s hummers, and helped me overcome my f l a t l a n d e r ways. Lee has always been there with q u e s t i o n s , i d e a s and support. Fred Ganders, Judy Myers, and Jamie Smith o f f e r e d h e l p f u l advice along the way and a s s i s t e d c o n s i d e r a b l y by r e a d i n g the manscript and h e l p i n g with r e v i s i o n s . Kurt Cehak gave l o n g hours of help with mapping t e r r i t o r i e s and with other t e d i o u s data c o l l e c t i n g . C a r l Whitney p a t i e n t l y helped with computer programing and provided much needed moral support. I thank Ethen P e r k i n s f o r wanting t o read t h i s s t o r y and encouraging me to wr i t e i t . He gave h i s love and encouragement throughout, suggested r e v i s i o n i n the d r a f t i n g of the manuscript, gave b o t a n i c a l a d v i c e and helped i n the f i e l d work. Rachel Ruth Per k i n s has been a wonderfully rewarding d i v e r s i o n during the l a s t year. Many ot h e r s have knowingly and sonetimes unknowingly given me help and support, and I thank them here a l s o . Of course, without the hummingbirds and the p l a n t s none of t h i s would have been p o s s i b l e . 1 INTRODUCTION P o l l e n d i s p e r s a l i s of major importance i n the completion of the s e x u a l phase of f l o w e r i n g plant l i f e c y c l e s . T r a n s f e r of p o l l e n and seed d i s p e r s a l are the means by which p l a n t genes move through p o p u l a t i o n s , and s e x u a l r e p r o d u c t i o n and conseguent g e n e t i c recombination change or maintain the g e n e t i c makeup of a p o p u l a t i o n . (Stebbins 1950, Grant 1958,1971, F a e g r i and van der P i j l 1966, P r o c t o r and Yeo 1972, Covich 1974, flacior, 1974). ft wide v a r i e t y of mechanisms i n c l u d i n g wind, water and the v i s i t a t i o n s of v a r i o u s i n s e c t s , b i r d s , and mammals have been i d e n t i f i e d as means of p o l l e n d i s p e r s a l . P l a n t s are o f t e n h i g h l y s p e c i a l i z e d to i n c r e a s e the e f f e c t i v e n e s s o f a p a r t i c u l a r system of p o l l i n a t i o n . These a d a p t a t i o n s are apparent i n the wide range i n f l o r a l morphology seen, from the f a i r l y i n c o nspicuous f l o w e r s of wind p o l l i n a t e d grasseis to the showy f l o w e r s of some o r c h i d s (Knuth 1908, P e r c i v a l 1965, F a e g r i and van der P i j l 1966, P r o c t o r and Yeo 1972) . For s u c c e s s f u l p o l l i n a t i o n by an animal, the p l a n t must accomplish t h r e e t h i n g s . F i r s t the p o t e n t i a l p o l l i n a t o r must be a t t r a c t e d , u s u a l l y by a s p e c i f i c food reward (nectar or p o l l e n ) . The presence o f a food source and the c o r r e c t procedure f o r o b t a i n i n g i t may be cued by a v a r i e t y of f l o r a l s i g n a l s i n c l u d i n g c o l o r , shape, and p a t t e r n i n g of the f l o w e r s . Non-visual s i g n a l s i n c l u d e v a r i o u s odors, or even t a c t i l e s i g n a l s i n the form of tongue and body guides (van der P i j l 1960,1961, P e r c i v a l 1965, F a e g r i and van der P i j l 1966, P r o c t o r and Yeo 1972, Macior 1971). Second, the v i s i t o r must v i s i t more 2 than one i n d i v i d u a l o f the same s p e c i e s . T h i s can be accomplished i f the v i s i t o r does not become s a t i a t e d at the f i r s t flower and p i c k s up s i g n a l s from the second t h a t i n d i c a t e where more food may be found {Heinrich and Raven 1972, Covich 1974, H e i n r i c h 1975). T h i r d , t h e shape of the f l o w e r and p r e c i s e p o s i t i o n i n g of the r e p r o d u c t i v e p a r t s must be such t h a t the p o l l e n d e posited on the v i s i t o r i s i n a l o c a t i o n where i t w i l l c o n t a c t the stigma of the next flower v i s i t e d ( P e r c i v a l 1965, F a e g r i and van der P i j l 1966, P r o c t o r and Yeo 1972). S p e c i f i c animal p o l l i n a t o r s possess adaptations which e x p l o i t the r e s o u r c e s p r o v i d e d by a p l a n t . These may be s t r u c t u r a l a d a p t a t i o n s such as a tongue whose l e n g t h corresponds to the l e n g t h of a c o r o l l a tube, or a body shape which f i t s n e a t l y i n t o a flower ( P e r c i v a l 19 65, F a e g r i and van der P i j l 1966, P r o c t o r and Yeo 1972). The a d a p t a t i o n s may a l s o be b e h a v i o r a l , i n the case of a v i s i t o r f o r a g i n g a t a time when the flower i s open (Wolf 1970, Hosguin 1971, Heithaus 1974), or whose f e e d i n g behavior i s e s p e c i a l l y e f f e c t i v e i n e x t r a c t i n g food with the l e a s t amount of e f f o r t ( P e r c i v a l 1965, F a e g r i and van der P i j l 1966, P r o c t o r and Yeo 1972). In coadapted systems the s p e c i f i c mechanisms by which the p l a n t and i t s p o l l i n a t o r i n t e r a c t r e f l e c t the c h a r a c t e r i s t i c s of the s p e c i f i c i n d i v i d u a l s i n v o l v e d . H i g h l y coadapted p o l l i n a t i o n systems reduce p o l l e n wastage by i n e f f e c t u a l and o f t e n u n r e l i a b l e p o l l i n a t o r s and guarantee a food source t h a t i s f r e e frcm c o m p e t i t i o n by non-adapted animals {eg. Mosguin 1971, Macior 1971,1974). Whatever the mechanism of p o l l e n t r a n s p o r t , a major 3 q u e s t i o n concerns the e f f e c t of the p o l l e n d i s p e r s a l mechanism on p o l l e n flow and thus on gene flow and the g e n e t i c makeup o f the p o p u l a t i o n . V a r i a t i o n s i n p o l l i n a t o r b e h a v i o r w i l l a f f e c t gene flow i n d i f f e r e n t ways. The g e n e t i c s i g n i f i c a n c e of p o l l e n flow (hence p o l l i n a t o r behavior) w i l l a l s o depend very much on the breeding system o f t h e p l a n t p o p u l a t i o n . A p o l l i n a t o r t h a t f l i e s from f l o w e r to flower on one p l a n t before going on to the next, or forages i n a r e s t r i c t e d area, may r e s t r i c t o u t c r o s s i n g i n the p o p u l a t i o n , while a wide ranging f o r a g e r may i n c r e a s e o u t c r o s s i n g (Stebbins 1950, Grant 1971, P r o c t o r and Yeo 1972). A p o l l i n a t o r t h a t forages i n a r e s t r i c t e d area may cause more in b r e e d i n g i n a p l a n t s p e c i e s t h a t i s s e l f compatible than i n one that i s o b l i g a t e l y o u t c r o s s i n g . In order to determine the f u l l e f f e c t of p o l l i n a t o r behavior on p o l l e n and gene flow i t i s important to c o n s i d e r each i n d i v i d u a l p l a n t - p o l l i n a t o r system as a whole. T h i s i s e s p e c i a l l y important i n coadapted systems, where the f o r a g i n g behavior of the animal v i s i t o r i s o f t e n h i g h l y i n f l u e n c e d by v a r i o u s p l a n t components such as a t t r a c t i v e n e s s , p l a n t d e n s i t y , and the presence of other v i s i t a b l e p l a n t s p e c i e s (e. g. L e v i n 1969, Levin and K e r s t e r 1969a,1969b, Le v i n and Anderson 1970, Macior 1971,1974). Hummingbirds are p o l l e n v e c t o r s f o r many New World p l a n t s p e c i e s , and the c o a d a p t a t i o n of hummingbirds and many c f the p l a n t s they v i s i t i s w e l l documented (Grant and Grant 1966,1968). T y p i c a l hummingbird p l a n t s , most o f t e n p e r e n n i a l s p e c i e s , produce copious amounts of nectar which i s o f t e n l o c a t e d at the base of a long tube. I n order to f e e d , the b i r d 4 must brush a g a i n s t the stigmas and anthers of the f l o w e r while g a t h e r i n g n e c t a r thus p o l l i n a t i n g the f l o w e r ( P e r c i v a l 1965, F a e g r i and van der P i j l 1966, Grant 1966, Grant and Grant 1966,1968, P r o c t o r and Yeo 1972). The b i r d s have long narrow b i l l s , tongues adapted f o r l i c k i n g n e c t a r , and the a b i l i t y t o hover, a l l of which a i d the b i r d i n f e e d i n g from these f l o w e r s (Bent 1940, P e r c i v a l 1965, Grant and Grant 1968, P r o c t o r and Yeo 1972). So as the b i r d s f o r a g e they d i s p e r s e p o l l e n w i t h i n the p l a n t p o p u l a t i o n s . 5 THE COMPONENTS OF A HUMMINGBIRD-MEDIATED POLLINATION SYSTEM What are the e f f e c t s o f hummingbird f o r a g i n g on p o l l e n d i s p e r s a l ? In order to answer t h i s g u e s t i o n , I s t u d i e d the i n t e r a c t i o n s between the f o l l o w i n g components of a plant-hummingbird system: t e r r i t o r i a l b e havior, p l a n t f l o w e r i n g times, f o r a g i n g f l i g h t d i s t a n c e , p o l l e n c a r r y over, other p o l l i n a t o r s , and p l a n t breeding systems. Hummingbird f o r a g i n g behavior i s a complex set of b e h a v i o r a l p a t t e r n s i n f l u e n c e d by many f a c t o r s such as f l o r a l n e c t a r p r o d u c t i o n , p l a n t d e n s i t y , the presence of other b i r d s and the energy r e q u i r e d f o r f o r a g i n g (Bene" 1945, Grant and Grant 1968, Wolf 1969, Wolf et a l . 1972, L i n h a r t 1973, Schemske 1975, Gass et a l . 1976, and o t h e r s ) . In c o n s i d e r i n g f o r a g i n g behavior as the major means of p o l l e n d i s p e r s a l I conc e n t r a t e d on two major areas w i t h i n the f o r a g i n g behavior complex: 1) the r e l a t i o n s h i p of t e r r i t o r i a l behavior to f o r a g i n g behavior, and 2) how f a r a b i r d f l i e s between flowers and p l a n t s on a f o r a g i n g f 1 i g h t . 6 T e r r i t o r i a l Behavior And P l a n t Flower ing Times Probably the most important determinant of the f o r a g i n g p a t t e r n s of many hummingbird s p e c i e s i s t h e i r e s t a b l i s h m e n t of fee d i n g t e r r i t o r i e s . These t e r r i t o r i e s are a g g r e s s i v e l y defended a g a i n s t c o n s p e c i f i e s , members of other hummingbird s p e c i e s , and even l a r g e bees. Breeding and migrating hummingbirds of both sexes defend t e r r i t o r i e s (Kobbe 190 0, Bent 1940, P i t e l k a 19 42, Pickens 1944, Armitage 1955, Cody 196 8, S t i l e s and Wolf 1970, Gass 1974, Wolf 1969, 1975a, Boyden 1977). The s i z e o f these t e r r i t o r i e s seems to be determined by the a v a i l a b i l i t y of enough ne c t a r from the l o c a l p l a n t s t o supply an i n d i v i d u a l b i r d ' s d a i l y needs (Wolf 1969,1970, S t i l e s and Wolf 1970, wclf and Hainsworth 1971, Gass 1974, Gass e t a l . 1976, Carpenter and MacMillan 1976, Kpdric-Brown and Brown 1978). How do these t e r r i t o r i e s a f f e c t p o l l e n d i s p e r s a l i n the p l a n t p o p u l a t i o n ? Two s t u d i e s have concluded that p o l l e n flow i n plant-hummingbird p o l l i n a t i o n systems would be r e s t r i c t e d to a t e r r i t o r y , thus l i m i t i n g o u t c r o s s i n g i n the p l a n t p o p u l a t i o n (Grant and Grant 1968, L i n h a r t 1973) . Grant and Grant (1968) based t h e i r c o n c l u s i o n s on o b s e r v a t i o n s that an i n d i v i d u a l Costa's hummingbird (Calypte costa) spent the major p a r t c f i t s f o r a g i n g time w i t h i n i t s t e r r i t o r y , and that very few other i n d i v i d u a l s i n t r u d e d i n t o the t e r r i t o r y during t h e i r study. L i n h a r t (1973) s t u d i e d the d i s p e r s a l of marked p o l l e n f o r both t e r r i t o r i a l and n o n - t e r r i t o r i a l hummingbird s p e c i e s . For s t r o n g l y defended t e r r i t o r i e s he found t h a t there was a sharp d e c l i n e i n p o l l e n movement at the t e r r i t o r i a l boundary. In an 7 area where t e r r i t o r i e s were not as s t r o n g l y defended and where he noted f l i g h t s by i n t r u d e r s i n t o t e r r i t o r i e s , p o l l e n d i s p e r s a l again dropped s h a r p l y a t the t e r r i t o r y boundary but marked p o l l e n was found as f a r as 100 m from i t s source. These s t u d i e s provide s t r o n g evidence f o r the r e s t r i c t i o n of p o l l e n flow by t e r r i t o r i a l behavior. The o b s e r v a t i o n p e r i o d i n both of these s t u d i e s was g u i t e s h o r t , two days i n the study done by Grant and Grant and three to f i v e days i n L i n h a r t ' s study. P o s s i b l y due t o such s h o r t o b s e r v a t i o n times the authors d i d not account f o r the f a c t t h a t t e r r i t o r i a l boundaries may change d u r i n g the course of a f l o w e r i n g season. In f a c t t h e i r c o n c l u s i o n s i m p l i c i t l y assume t h a t t e r r i t o r i e s dp not change. Gass{1974, Gass et a l . 1976) showed t h a t the numbers and s i z e s of t e r r i t o r i e s w i t h i n h i s study areas changed c o n s i d e r a b l y throughout the season. He found t h a t as the number of f l o w e r s i n a meadow i n c r e a s e d , the number of t e r r i t o r i e s i n c r e a s e d and t h e i r s i z e s decreased. Boundary changes a l s o occurred when b i r d s a r r i v e d at or l e f t a meadow. Thus I f e l t i t important t o c o n s i d e r the r e l a t i o n s h i p between t e r r i t o r i a l b e havior and p o l l e n flow f o r the major p a r t of a f l o w e r i n g season. I f p l a n t s remain i n flower l o n g e r than t e r r i t o r i a l boundaries remain unchanged, the r e s t r i c t i o n of outbreeding p r e d i c t e d by the previous s t u d i e s would be reduced. T h e o r e t i c a l l y , i f a p l a n t remains i n f l o w e r throughout a sequence of changes i n t e r r i t o r i a l boundaries, the r e s t r i c t i o n s imposed by a s i n g l e s e t of boundaries may be l e s s s i g n i f i c a n t on a long term time s c a l e . T h e r e f o r e , i t i s important t o determine 8 when and f o r how l o n g the p l a n t s i n the area flower. Foraging F l i g h t Distances What are the dynamics o f p o l l e n d i s p e r s a l w i t h i n f e e d i n g t e r r i t o r i e s ? As a b i r d moves from flower to f l o w e r and p l a n t to pl a n t f e e d i n g on nectar i t i s a l s o d i s p e r s i n g p o l l e n ; the length of these f l i g h t s i s the b a s i c b u i l d i n g b lock f o r p o l l e n movement w i t h i n t e r r i t o r i e s and p l a n t p o p u l a t i o n s . I f the flowers v i s i t e d are c l o s e together p o l l e n flow w i l l be r e s t r i c t e d whether t e r r i t o r i a l boundaries r e s t r i c t f o r a g i n g or not. The l o n g e r the f l i g h t s the g r e a t e r the e f f e c t o f t e r r i t o r i a l boundaries. Knowledge of the dynamics o f the b i r d ' s f o r a g i n g f l i g h t s i s e s s e n t i a l i n understanding p o l l e n f l o w dynamics i n a plant-hummingbird system. P o l l e n Carry. Over I s a l l the p o l l e n p i c k e d up from one flower d e p o s i t e d on the next f l o w e r the b i r d v i s i t s or does some of t h i s p o l l e n remain on the b i r d to be d e p o s i t e d on the t h i r d , f o u r t h , f i f t h , or f i f t i e t h f l o w e r v i s i t e d ? F oraging f l i g h t d i s t a n c e s p r o v i d e an estimate of the p o t e n t i a l f o r p o l l e n movement. However, p o l l e n flow d i s t a n c e s d e r i v e d from t h i s measure w i l l be g r e a t l y a f f e c t e d by p o l l e n c a r r y over d i s t a n c e s . P r e v i o u s s t u d i e s of p o l l i n a t o r mediated p o l l e n flow have e i t h e r ignored the quest i o n e n t i r e l y (e. g. L e v i n and Ke r s t e r 1968, B e a t t i e 1976) or made a r a t h e r vague assumption as to how 9 f a r p o l l e n i s " c a r r i e d over" (Kerster and L e v i n 1968, L e v i n and K e r s t e r 1969a,b; L e v i n et a l . 1971). The problem i s not i n f a i l i n g t o r e a l i z e t h a t the p o l l e n c a r r y over q u e s t i o n must be asked, but i n f i n d i n g an e x p e r i m e n t a l technique t h a t would provide the i n f o r m a t i o n needed t o answer i t . In only one case t h a t I know of (Levin and Berube 1972) were any experiments done to determine the e x t e n t of p o l l e n c a r r y over. In t h a t study c a r r y over of b u t t e r f l y d i s p e r s e d Phlox p o l l e n was estimated f o r c o n s p e c i f i c p o l l e n by determining the number of p o l l e n tubes i n the s t y l e s a f t e r p o l l i n a t i o n (Levin and Berube s t a t e d t h a t these p l a n t s were s e l f - i n c o m p a t i b l e and that the number of tubes i s i n d i c a t i v e of o u t c r o s s p o l l e n ) . For i n t e r s p e c i f i c c r o s s e s , d i r e c t p o l l e n counts c o u l d be made because of d i f f e r e n c e s i n p o l l e n s i z e between the s p e c i e s . P o l l e n c a r r y over i n these experiments d i d not extend beyond the f i f t h f l o w e r v i s i t e d (Levin and Berube 1972). Other P o l l i n a t o r s Hummingbirds may not be t h e s o l e p o l l i n a t o r s of the p l a n t s i n a system. I t i s important to note the presence and behavior of other p o t e n t i a l p o l l i n a t o r s s i n c e they c o u l d be c o n t r i b u t i n g t o p o l l e n movement w i t h i n the p o p u l a t i o n s even though t h e i r o v e r a l l i n f l u e n c e may be c o n s i d e r a b l y s m a l l e r t h a t t h a t of the hummingbirds. 10 P l a n t Breeding Svstems In order t o r e l a t e the dynamics of p o l l e n flow t o gene flow i n a plant p o p u l a t i o n , the s p e c i f i c breeding systems of the p l a n t s must be known. I t i s i m p o s s i b l e t o c o r r e l a t e p o l l e n flow with gene flow i n a p o p u l a t i o n without knowing whether or not p l a n t s are s e l f i n c o m p a t i b l e. For example, i f a p l a n t i s s e l f i n c o m p a t i b l e the p o l l e n t r a n s f e r e d from one flower t o other f l o w e r s on the same p l a n t w i l l not be e f f e c t i v e i n producing seed, only t h e p o l l e n t r a n s f e r e d from another p l a n t w i l l be s u c c e s s f u l i n f e r t i l i z i n g an ovule and thus be the important determinant of gene flow. k d e s c r i p t i o n o f the i n t e r a c t i o n s between the components d i s c u s s e d above probably would not p o r t r a y a completely a c c u r a t e p i c t u r e of the t o t a l dynamic i n t e r a c t i o n s o c c u r r i n g i n nature. However, they would provide enough i n f o r m a t i o n about the system to allow d e s c r i p t i o n o f the major e f f e c t s of hummingbird f o r a g i n g on p o l l e n flow. 11 METHODS The Stjadj Area T h i s study was done i n J u l y and August 1975 i n two suba l p i n e meadows { a l t i t u d e 2200-2500 m), l o c a t e d on t a l u s s l o p e s above G r i z z l y Lake i n the Sa l m o n - T r i n i t y A l p s P r i m i t i v e Area of northern C a l i f o r n i a . The meadows are s m a l l ; meadow 1 i s roughly 500 m2 and meadow 2 roughly 1300 m2. The meadows are q u i t e steep {30-40°) and surrounded by g r a n i t e o u t c r o p s . The outcrops provided e x c e l l e n t vantage p o i n t s from which o b s e r v a t i o n s o f the hummingbirds c o u l d be made. These are the same as meadows 1 and 2 d e s c r i b e d by Gass (1974, Gass et a l . , 1976). The hummingbirds v i s i t i n g these meadows were emigrating female and j u v e n i l e Bufous hummingbirds (Selasghorus r u f u s ) . These b i r d s winter i n c e n t r a l Mexico and may migrate as f a r north as Alaska each s p r i n g t o breed. F o l l o w i n g the bree d i n g season they r e t u r n t o Mexico v i s i t i n g f l o w e r i n g meadows of the Coast, C a s c a d e - S i e r r a and fiocky Mountain ranges during the t r i p (Bent 1940, Grant and Grant 1967,1968, P h i l l i p s 1975) . T h i s southward m i g r a t i o n u s u a l l y occurs i n two major waves with the males preceeding the female and j u v e n i l e b i r d s ( P h i l l i p s 1975). During m i g r a t i o n the b i r d s stop and s e t up feeding t e r r i t o r i e s i n s u b a l p i n e meadows along the rout e . I t i s not c l e a r how lonq the b i r d s remain i n one area but they may hold t e r r i t o r i e s from l e s s than a day to s e v e r a l weeks before moving on (Gass and 12 Lynch, i n p r e p a r a t i o n ) . They u s u a l l y begin t o a r r i v e at the G r i z z l y Lake meadows i n e a r l y J u l y and are gone by e a r l y September. T h i s c o i n c i d e s with the f l o w e r i n g times of the p l a n t s i n these meadows (Gass 1974, Gass et a l . 1976). In the G r i z z l y Lake meadows the b i r d s f e d predominantly on Indian paintbrush ( C a s t i l l e j a miniata) and columbine f A g u i l e g i a formosa). These are p e r e n n i a l s p e c i e s t h a t e x h i b i t the morphology of t y p i c a l hummingbird flowers ( F i g . 1) and flower abundantly i n the study areas. Although the predominant p l a n t s p e c i e s v i s i t e d by hummingbirds i n meadow 1 was columbine and i n meadow 2 was I n d i a n paintbrush, both s p e c i e s were present i n both meadows. Because of t h e heavy s n o w f a l l p r i o r to the 1975 f i e l d season, f l o w e r i n g was delayed almost a month. Conseguently my ob s e r v a t i o n s d i d not begin u n t i l the l a s t week of J u l y . Most of the data f o r t h i s t h e s i s were gathered d u r i n g August o f th a t year. T e r r i t o r i a l Behavior To determine changes i n s i z e , shape, numbers and p o s i t i o n i n g of t e r r i t o r i e s i n the meadows, I noted perch l o c a t i o n s , f o r a g i n g f l i g h t s and where chases of i n t r u d e r s occurred f o r each t e r r i t o r y h older i n each meadow approximately every t h r e e days. With t h i s i n f o r m a t i o n the boundary o f a t e r r i t o r y c o u l d be d e f i n e d and p l o t t e d on s c a l e maps of the meadows. Host days the t e r r i t o r i a l boundaries i n a meadow co u l d be determined i n about two hours. The areas o f t e r r i t o r i e s were 13 F i g u r e 1: a. Columbine { A s u i l e a i a formosa) paintbrush ( C a s t i l l e j a miniata) 15 determined l a t e r by weighing paper c u t o u t s of each and c o n v e r t i n g t h i s measurement i n t o square meters. a f t e r the t e r r i t o r i a l boundaries were determined the number of f l o w e r s i n each meadow was counted. Counts of the number of i n f l o r e s c e n c e s were made f o r Indian paintbrush and of the number o f i n d i v i d u a l f l o w e r s f o r columbine. These techniques were the same as those used by Gass i n h i s 1974 and 1976 s t u d i e s (Gass e t a l . 1976). f o r a g i n g Behavior I recorded the l o c a t i o n and sequence of patches (roughly e q u i v a l e n t t o an i n d i v i d u a l p l a n t , see below) v i s i t e d on each f o r a g i n g f l i g h t on l a r g e s c a l e maps of the meadows, and gathered three types of i n f o r m a t i o n from each f l i g h t . F i r s t , I determined whether the f l i g h t was e n t i r e l y w i t h i n , o u t s i d e o f , or across t e r r i t o r i a l boundaries. Second, t o determine f l i g h t d i s t a n c e s I c a l c u l a t e d the s t r a i g h t l i n e d i s t a n c e from patch to patch within each f o r a g i n g f l i g h t . I a l s o c a l c u l a t e d the d i s t a n c e from the l a s t patch v i s i t e d i n a f l i g h t t o the perch and from the perch to the f i r s t patch v i s i t e d . During a f o r a g i n g f l i g h t a b i r d seldom forages i n a s t r a i g h t l i n e and may even c i r c l e back to feed a second time at the f i r s t patch i t v i s i t e d . Thus the maximum d i s t a n c e of p o t e n t i a l p o l l e n d i s p e r s a l f o r a f l i g h t may not always be the same as the d i s t a n c e between the f i r s t and l a s t patches v i s i t e d . The data presented are based on the maximum p o t e n t i a l p o l l e n flow d i s t a n c e i n a l l cases. P r o b a b i l i t i e s of p o t e n t i a l p o l l e n flow f o r a s p e c i f i c d i s t a n c e were d e r i v e d from data over the d u r a t i o n of the study by 16 determining the t o t a l number o f v i s i t s w i t h i n t h a t s p e c i f i c d i s t a n c e and d i v i d i n g t h i s by the t o t a l number of v i s i t s observed. F i n a l l y , I recorded i n f o r m a t i o n on f o r a g i n g behavior w i t h i n a patch by r e c o r d i n g the number of fl o w e r s and/or i n f l o r e s c e n c e s and the number of potentia11y v i s i t a b l e flowers and/or i n f l o r e s c e n c e s f o r each patch. From my o b s e r v a t i o n posts I could not p o s i t i v e l y determine whether a patch was equal to an i n d i v i d u a l p l a n t . To determine how w e l l the patches corresponded t o a s i n g l e p l a n t , I recorded the number of flowers (columbine and I n d i a n p a i n t b r u s h ) , or i n f l o r e s c e n c e s (Indian paintbrush) with v i s i t a b l e flowers f o r each o f f i f t y randomly chosen p l a n t s l o c a t e d along t r a n s e c t s through each of the meadows. I determined the f l i g h t d i s t a n c e between fl o w e r s cr i n f l o r e s c e n c e s within a patch by measuring the d i s t a n c e from a randomly chosen fl o w e r or i n f l o r e s c e n c e on each p l a n t t o i t s nearest neighbor. ; I gathered data on columbine and In d i a n p a i n t b r u s h v i s i t s f o r both meadows. The f i n a l a n a l y ses were based on data gathered f o r the predominant s p e c i e s i n each meadow. 17 P l a n t Ilowering Times I determined the d u r a t i o n of f l o w e r i n g o f t h i r t y marked i n d i v i d u a l s of each s p e c i e s . H a l f were observed f o r the e n t i r e study season. The others were added to t h i s group about halfway through the season so that any d i f f e r e n c e s i n f l o w e r i n g time d u r i n g the season c o u l d be accounted f o r . A l l the p l a n t s had some flo w e r s i n bloom at the s t a r t of the study. I checked these p l a n t s about every three days and recorded whether or not they s t i l l had flowers i n bloom. I assumed t h a t i f a b i r d v i s i t e d a f l o w e r , p o l l e n c o u l d be t r a n s f e r e d to and from that flower. Thus I d e f i n e d the f l o w e r i n g time of a p l a n t as the time d u r i n g which any of i t s flowers were at a s t a g e t h a t a hummingbird would v i s i t . I determined which stages were " v i s i t a b l e " by f o l l o w i n g the f l o w e r i n g sequence f o r each s p e c i e s , d i v i d i n g t h i s sequence i n t o a number of d i s t i n c t s taqes, and r e c o r d i n g which of these staqes 1 observed hummingbirds v i s i t i n g ( F i g s . 7,8). P o l l e n Carry. Over To determine the extent of hummingbird mediated p o l l e n c a r r y over I d i d a s e r i e s of experiments i n the l a b o r a t o r y i n which l i v e hummingbirds with no p o l l e n on them v i s i t e d a s i n g l e i n t a c t f u c h s i a f l o w e r ( F u c h s i a hyprida) and then v i s i t e d a s e r i e s of emasculated f l o w e r s . As the b i r d fed on these flowers I recorded the sequence o f f e e d i n g ; a b i r d was allowed to make more than one jab i n t o a flower to feed but was not allowed to r e t u r n to a flower a f t e r having v i s i t e d another. I presented ten 18 flowers as p o l l e n " s i n k s " i n f o u r experiments and i n two experiments I used twenty f l o w e r s . The stigmas of the flowers v i s i t e d were removed and c l e a r e d using 10% KOH and then squashed on microscope s l i d e s t o spread out the t i s s u e . T o t a l p o l l e n counts sere made f o r each stigma and a l s o f o r ten stigmas of u n v i s i t e d f l o w e r s t o t e s t my assumption t h a t stigmas were indeed p o l l e n f r e e p r i o r t o an experiment. Four Rufous hummingbirds (females and j u v e n i l e males} were used i n the experiments, which were performed i n the a v i a r y where these b i r d s were kept. Fuchsia f l o w e r s were used because the experiments were done i n October, when n e i t h e r columbine or I n d i a n paintbrush were i n flo w e r . F u c s hia i s a domesticated p l a n t that f l o w e r s abundantly i n autumn and hummingbirds are known t o v i s i t i t s b r i g h t p i n k i s h - r e d blossoms ( F i g . 2). P o l l e n i s r e l e a s e d abundantly i n s t i c k y s t r a n d s from the anthers and the s i n g l e l a r g e stigma becomes r e c e p t i v e b e f o r e the anthers mature. Other P o l l i n a t o r s In order to o b t a i n i n f o r m a t i o n about non-hummingbird v i s i t o r s t o columbine and In d i a n p a i n t b r u s h I observed the behavior of v a r i o u s i n s e c t v i s i t o r s and then c o l l e c t e d them f o r l a t e r i d e n t i f i c a t i o n . I a l s o monitored the presence of these v i s i t o r s i n the meadows at v a r i o u s times of day. 19 F i g u r e 2: F u c h s i a (Fuchsia hybrifla) 20 21 Plant Breeding Systems In order t o determine whether columbine or Indian paintbrush were s e l f - c o m p a t i b l e I d i d a s e r i e s of bagging experiments. Tables 711 and VIII summarize the f i e l d experiments that were done. Flowers of columbine or i n f l o r e s c e n c e s of I n d i a n p a i n t b r u s h were bagged while s t i l l i n bud and then p o l l i n a t e d by hand as they came i n t o f l o w e r ; any flowers not used i n the experiments were c l i p p e d o f f . When the seeds i n these experimental f l o w e r s had begun to develop the c a p s u l e s were c o l l e c t e d , as were a random sample of seed c a p s u l e s from the p o p u l a t i o n . L a t e r I counted the number of good seeds per capsule f o r each flower. I judged a seed as being "good" i f i t was l a r g e and f a i r l y normal i n shape. I d i d not attempt t o germinate the seeds. I d i d not do any experiments using emasculated Indian paintbrush f l o w e r s because they could not be emasculated without damaging the f l o w e r s . To determine the t i m i n g o f s t i g m a t i c r e c e p t i v i t y I removed stigmas of f l o w e r s at v a r i o u s developmental s t a g e s and s t a i n e d them with l a c t o p h e n o l cotton blue (Sass 1958). Blue s t a i n i n g of the s t i g m a t i c s u r f a c e , presence of p o l l e n g r a i n s or morphological changes were c o n s i d e r e d t o be i n d i c a t i o n s of r e c e p t i v i t y . The s l i d e s were made permanent using Hoyer's mounting medium (Alexopoulos and Beneke 1952)* 22 RESULTS T e r r i t o r i a l Behavior I expected marked changes i n the s i z e , number, shape and p o s i t i o n i n g of t e r r i t o r i e s i n each meadow du r i n g the season as i n Gass 1974, and Gass et a l . 1976. The occurance and extent o f these changes during my study are g u i t e c l e a r ( F i g s . 3-6). In meadow 2 the mean s i z e o f t e r r i t o r i e s was i n v e r s e l y r e l a t e d to the number of t e r r i t o r i e s i n the meadow {Fig. 6). Because not a l l of meadow 1 came i n t o flower at once, t e r r i t o r y f ormation was r e s t r i c t e d to the densely f l o w e r e d upper part of the meadow at f i r s t , and the t e r r i t o r i e s formed t h e r e were small..Thus the r e l a t i o n s h i p of average t e r r i t o r y s i z e and numbers of t e r r i t o r i e s i s not simple f o r t h i s meadow. Pl a n t Flowering Time F i g u r e s 7 and 8 are drawings of the b a s i c f l o w e r i n g stages f o r each s p e c i e s . The hummingbirds v i s i t e d columbine frcm the time the buds began to open (stage 3) u n t i l the o l d flo w e r s had only a couple of spurs remaining (stage 6). They v i s i t e d I n dian paintbrush from stage 3 to stage 5. Indian p a i n t b r u s h flowers beyond stage 5 were dry and produced l i t t l e or no ne c t a r . P l a n t s of both s p e c i e s remain i n flower f o r a t l e a s t a month (Tables I and I I ) . The f l o w e r i n g time may even be longer than t h i s because a l l the p l a n t s on my t r a n s e c t s were i n flower 23 F i g u r e 3: Changes i n s i z e and shape o f t e r r i t o r i e s i n meadow 1. The major rock outcrops have been drawn i n . Shaded areas i n d i c a t e t e r r i t o r i e s . 24 AUG-11 AUG-16 AUG-20 5 m / c m > 25 Fi g u r e 4: Changes i n s i z e and shape of t e r r i t o r i e s i n meadow 2, Symbols as i n F i g . 3. 27 F i g u r e 5: Changes i n t e r r i t o r y numbers (a) and s i z e (b) meadow 1. 4 1 1 1 r-l 1 h-28 1 5 9 13 17 21 25 JULY 1975 AUG •ATE (4 W H 400 _ 300 1 EDO 1 F' loo 1 0 28 1 JULY 5 ^ 13 17 21 25 •ATE AUG 29 F i g u r e 6: Changes i n t e r r i t o r y numbers (a) and s i z e (b) meadow 2. 31 F i g u r e 7: Flowering stages i n columbine. Hummingbirds v i s i t stages 3-6. Anthers begin t o dehisce at stage U. Stigmas become r e c e p t i v e at stage 5 (arrows i n d i c a t e s t i g m a s ) . Nectar i s present a t stages 3-6. A l l measurements i n d i c a t e average l e n g t h s i n m i l l i m e t e r s . 32 33 F i g u r e 8: Flowering stages i n I n d i a n p a i n t b r u s h . Hummingbirds v i s i t s t a g e s 3-5. Anthers begin t o dehisce a t stage U. Stigmas are r e c e p t i v e by stage k (see t e x t p. 59). Nectar i s present at stages 3-5. A l l measurements i n d i c a t e average lengths i n m i l l i m e t e r s . 34 V Table I Length of f l o w e r i n g time f o r Columbine Number of jalants i n bloom Date § £ 2 U £ 1 Grouj) 2 31 J u l y 15 2 Aug 15 5 Aug 14 9 Aug 13 12 Aug 12 15 16 Aug 10 15 19 Aug 7 14 22 Aug 7 13 lahle I I Length of f l o w e r i n g time f o r Indian p a i n t b r u s h . Number of p l a n t s i n bloom Date Group 1_ Group 2 30 J u l y 15 2 Aug 15 5 Aug 15 8 Aug 15 9 Aug 15 12 Aug 14 15 15 Aug 12 15 19 Aug 11 15 22 Aug 8 15 37 when I began monitoring them and the m a j o r i t y were s t i l l i n fl o w e r a t the end o f my study season. Foraging Behavior My o b s e r v a t i o n s confirmed the c o n c l u s i o n s o f Grant and Grant (1968), L i n h a r t (1973) and others (eg. S t i l e s 1971, Wolf et a l . 1972) t h a t hummingbirds tend t o r e s t r i c t t h e i r f o r a g i n g to w i t h i n t h e i r t e r r i t o r i e s (Table I I I ) . In t e r r i t o r i e s c o n t a i n i n g Delphinium c a r d i n a l e (Grant and Grant 1968) 88% of the f l i g h t s observed were e n t i r e l y w i t h i n t e r r i t o r i e s . In my study 89% of the f l i g h t s i n the columbine meadow (meadow 1) and 975? of the f l i g h t s i n the Indian paintbrush meadow were e n t i r e l y w i t h i n t e r r i t o r i a l boundaries. A f o r a g i n g f l i g h t as I've def i n e d i t begins with a f l i g h t from a perch t o a patch of f l o w e r s . The b i r d feeds from one or more f l o w e r s then may f l y to one or more other patches and feed. F i n a l l y i t f l i e s back t o a perch. During a f l i g h t a b i r d may a l s o chase other b i r d s or bees or hawk f o r i n s e c t s . I found i t convenient i n determining f o r a g i n g f l i g h t d i s t a n c e s t o d i v i d e a f o r a g i n g f l i g h t i n t o t h r e e s t a g e s : 1) The f l i g h t from a perch to a patch (or a patch to a perc h ) . 2) F l i g h t s between patches. 3) F l i g h t s between flowers w i t h i n a patch. The majo r i t y o f f l i g h t s between patches were l e s s than 2 m i n l e n g t h ( F i g s . 9-12). The mean f l i g h t d i s t a n c e between patches i n f o r a g i n g f l i g h t s was 1.8+.09 m (standard e r r o r ) f o r columbine T a b l e I I I The i n f l u e n c e of t e r r i t o r i a l boundaries on hummingbird f o r a g i n g f l i g h t s . Meadow 1 Meadow 2 F l i g h t s .892(431) .970(195) e n t i r e l y w i t h i n t e r r i t o r i a l boundaries F l i g h t s e n t i r e l y .017 (8) .005(1) o u t s i d e of any t e r r i t o r y F l i g h t s which c r o s s e d .091 (44) .025(5) t e r r i t o r i a l boundaries T o t a l f l i g h t s 483 201 Numbers i n d i c a t e p r o p o r t i o n of t o t a l f l i g h t s observed. Numbers i n parentheses i n d i c a t e number of f l i g h t s . 39 F i g u r e 9: Bean f l i g h t d i s t a n c e between patches of Columbine. Bars i n d i c a t e standard e r r o r s . 40 B 71 61 • S i Al 14 31 51 l l E5 " 10 4 3 3310 EE )( 14.. I ? - 4 X * 1 41 BE 1 f I 16 1G I 0 -I 1 1 1 1 1 h 30 1 JULY 6 8 10 12 14 16 18 20 1975 AUG DATE 41 F i g u r e 1 0 : Mean f l i g h t d i s t a n c e between patches of Indian paintbrush. Bars i n d i c a t e standard e r r o r s . 42 6 • 7.5 7.0.. G.O.. 5 . a . 5.0.. 4 .5. 4.O.. 3 . 5 . 3*0. S . 5 . S.O.. 1.0.. 0 . 5 . O.Q + S4 1B3B g m B 11 5 113 I SO 6 I 30 '1 4 6 8, JQ 12 14 16 18 20 IMI V 1 9 7 5 J U L Y A U G • A T E 43 Fig u r e 11: Frequency d i s t r i b u t i o n of d i s t a n c e s between s u c c e s s i v e l y v i s i t e d Columbine patches. 44 110 100... 90... BO .. 70 .. GO .. 50 ± X 40 i 30 SO .. 10 X X X x x — i — i — i — i X x x x X x x x x x i , 1 x i 0 1 5 3 4 5 6 7 B 9 10 11 IS 13 FLIGHT D I STANCE CM) 45 F i g u r e 12: Frequency d i s t r i b u t i o n of d i s t a n c e s between s u c c e s s i v e l y v i s i t e d Indian p a i n t b r u s h patches. 110 100 .. 30 BO .. 70 .. GO.. 50 .. X 40 .. 30 _ . X X SO .. 1 0 - X x x x x * X 0 1 i I I i ¥ x x i > < i i x i x x i y I 0 1 S 3 4 5 G 7 B 9 10 11 IS 13 14 FLIGHT D I STANCE CM) 47 t e r r i t o r i e s , and 1.9+.16 m f o r Indian p a i n t b r u s h t e r r i t o r i e s . T h i s tendancy of most of the f l i g h t s to be sh o r t has been found i n s t u d i e s of f l i g h t d i s t a n c e s of i n s e c t p o l l i n a t o r s (eg. L e v i n and K e r s t e r 1968,1969a,b; B e a t t i e 1976). C a l c u l a t i o n s of p o l l e n flow p r o b a b i l i t i e s based on l y on f o r a g i n g f l i g h t d i s t a n c e s i n d i c a t e a very high p r o b a b i l i t y o f s h o r t d i s t a n c e (about 2 m p o l l e n d i s p e r s a l (Table I V ) ) . The data ( F i g . 13) f o r f l i g h t d i s t a n c e s between a perch and a patch f o r meadow 1 i s l e s s constant over the season than the between-patch f l i g h t d i s t a n c e s ( F i g . 9). The i n c r e a s e i n t h i s f l i g h t d i s t a n c e towards the end of the season may correspond to an i n c r e a s e i n t e r r i t o r y s i z e a t t h i s time. W i t h i n patches a mean of 3.0+0.1 columbine f l o w e r s , or 3.3+0.2 Ind i a n paintbrush i n f l o r e s c e n c e s (7.5*0.5 Indian paintbrush flowers) were v i s i t e d . For both columbine and Indian p a i n t b r u s h the number of fl o w e r s i n a "patch" was g r e a t e r than the number on a p l a n t (Table V)., The e x t e n s i v e rhizome system o f columbine made i t d i f f i c u l t t o determine p r e c i s e l y what a " p l a n t " as a g e n e t i c i n d i v i d u a l was, thus my determination o f f l o w e r s per p l a n t f o r columbine may be an underestimate. I hypothesized t h a t as t e r r i t o r y s i z e i n c r e a s e d or decreased so would the l e n g t h of f o r a g i n g f l i g h t s . There was no c o r r e l a t i o n between the l e n g t h o f f l i g h t s between patches and t e r r i t o r y s i z e ( F i g . 14), but t h e r e was a p o s i t i v e c o r r e l a t i o n between t e r r i t o r y s i z e and perch to patch f l i g h t d i s t a n c e ( F i g . 14) i n d i c a t e d by my data. T h i s i m p l i e s that i t i s on the l e v e l of the perch to patch f l i g h t where the i n f l u e n c e o f t e r r i t o r y s i z e i s manifested, but more data a re needed to T a b l e IV Seasonal p r o b a b i l i t y of p o l l e n flow f o r Columbine and Indian paintbrush based on hummingbird f l i g h t d i s t a n c e s . Distance fm) Columbine Indian p a i n t b r u s h 0-2 .67 .67 2-4 .26 . 23 4-6 .03 . 06 6-8 . 03 .02 8-10 .01 .01 10-12 — . 01 12-14 .005 49 F i g u r e 13: The mean f l i g h t d i s t a n c e to and from perches. Bars i n d i c a t e standard e r r o r s . 50 c 9*0 B.5.. B.O.. 7.5.. 7 . a . 6.5. B.Q. 5*5. 5.O.. 4- 5 . 4.O.. 3*5. 3*0.. 5- 5 . 5.O.. i-a. 0.5. 0.0. _ 13 I 51 E9 E4 1G T 35 E42G il f H h 12 1 1 1 30 '1 JULY 6 1I5 1 0 1 2 • A T E 14 16 18 20 AUG < 51 T a b l e V R e l a t i o n s h i p between the number of fl o w e r s i n a patch to those on a plant, COLUMBINE Mean number Mean number of f l o w e r s / p l a n t o f f l o w e r s / p a t c h (N=5Q) J T o t a l season) 6 Aug 8.011.01 12.69*0.51 (N=520) 15 Aug 8.2+0.95 22 Aug 7.0+0.88 INDIAN PAINTBRUSH Mean number Mean number Mean number of f l o w e r s of i n f l o r e s c e n c e s o f i n f l o r e s c e n c e s per i n f l o r e s c e n c e per p l a n t per patch I I f 5 0 i (N=50) {Total season) 6 Aug 4.4*0.68 4.2+0.47 14.25+0.91 (N=162) 15 Aug 4.9+0.54 4.1+0.45 22 Aug 4.5+0.55 3.6+0.43 52 Fi g u r e 14: R e l a t i o n s h i p between t e r r i o r y s i z e and two c a t e g o r i e s of hummingbird f l i g h t d i s t a n c e s . x = F l i g h t s between a perch and the f i r s t or l a s t patch v i s i t e d r=0.91 p=0.0045 £=Flights between patches r=.45 p>0.1 54 con f i r m t h i s . P o l l e n Carry Over My working hypothesis f o r the p o l l e n c a r r y - o v e r experiments was t h a t p o l l e n would c a r r y over f a r t h e r than the f i r s t flower v i s i t e d , and would be de p o s i t e d i n d e c r e a s i n g numbers of g r a i n s on c o n s e c u t i v e f l o w e r s v i s i t e d . P o l l e n was c o n s i s t e n t l y deposited even to the t e n t h flower v i s i t e d , but there was no r e g u l a r p a t t e r n of d e c l i n e i n the amount of p o l l e n d e p o s i t e d on c o n s e c u t i v e f l o w e r s v i s i t e d (Pig.,15). In the two experiments i n which twenty f l o w e r s were presented as p o l l e n s i n k s t h e r e was no d e c l i n e i n the amount of p o l l e n d e p o s i t e d even t o the t w e n t i e t h flower. The range i n amount of p o l l e n deposited was high, probably due i n part t o v a r i a b i l i t y i n the f e e d i n g p o s i t i o n o f a b i r d . P o l l e n i s deposited by f u c s h i a i n l a r g e q u a n t i t i e s on a r e s t r i c t e d area of the b i r d ' s t h r o a t , thus the amount of p o l l e n deposited on a stiqma i s determined by the d i r e c t n e s s of c o n t a c t of the anthers on t h i s p o l l e n d e p o s i t i o n s i t e . None of the b i r d s i n these experiments were c o n s i s t e n t i n the way they touched the stigmas of the f l o w e r s they v i s i t e d and i n some cases b i r d s probed f l o w e r s without touching the stigmas a t a l l . I c a l c u l a t e d p o l l e n flow p r o b a b i l i t i e s based on p o l l e n c a r r y over t o the te n t h f l o w e r v i s i t e d , a c o n s e r v a t i v e estimate (Table VI). These data i n d i c a t e an i n c r e a s e i n the p r o b a b i l i t y of longer d i s t a n c e (past two meters) p o l l e n flow due to p o l l e n c a r r y over (compare with values i n Table I V ) . I t i s i n t e r e s t i n g 55 to note the d i f f e r e n c e s i n the e f f e c t p o l l e n c a r r y over has on p o l l e n flow p r o b a b i l i t i e s f o r columbine and Indian paintbrush. Because seven Indian paintbrush f l o w e r s were v i s i t e d per patch as compared to t h r e e columbine f l o w e r s , p o l l e n c a r r y over does not extend past the second I n d i a n paintbrush patch v i s i t e d , thus p o l l e n flow p r o b a b i l i t i e s at longer d i s t a n c e s do not d r a s t i c a l l y i n c r e a s e . I t i s c l e a r t h a t a l a r g e number of f l o w e r s blooming per p l a n t may have the e f f e c t o f decreasing the o v e r a l l d i s t a n c e of p o l l e n flow i n a p o p u l a t i o n . Other P o l l i n a t o r s My o b s e r v a t i o n s of i n s e c t v i s i t o r s t o columbine and Indian paintbrush are by no means ex h a u s t i v e . The most p r e v a l e n t i n s e c t v i s i t o r s t o columbine i n these meadows were bumblebees (Bombus S £ . ) . I n d i v i d u a l s gathered p o l l e n while c l i n g i n g to the a n t h e r s , and gathered n e c t a r by c r a w l i n g up the bundles of f i l a m e n t s i n t o spurs. These bees have a l s o been recorded i n other s t u d i e s as frequent v i s i t o r s to columbine (Grant 1952, Macior 1966, Chase and Baven 1975). The other f r e q u e n t l y seen v i s i t o r s to columbine were Syrphid f l i e s (Syrphidae) . These f l i e s would c l i n q to the anthers f o r long p e r i o d s o f time, p o s s i b l y f e e d i n g on p o l l e n . I a l s o observed them c r a w l i n g up i n t o the spurs of the f l o w e r s , presumably to feed on n e c t a r . The Syrphids probably do d i s p e r s e some p o l l e n although I f e e l t h a t they c o n t r i b u t e i n only a minor way t o p o l l e n flow i n these p o p u l a t i o n s . They do not c a r r y much p o l l e n on t h e i r bodies, have l i t t l e c o n t a c t with stigmas, and 56 F i g u r e 15: P o l l e n c a r r y over f o r hummingbird v i s i t e d f u c s h i a f l o w e r s . Bars i n d i c a t e ranges and standard e r r o r s . 57 1000 900 .. BOO .. 700 .. GOO .. 500 400 300 500 100 0 i f X X X X X X x H—I h H 1 h 0 1 E 3 4 5 G 7 B 9 10 11 IE 13 14 15 1G 17 IB 19 FLOWER NUMBER / 58 Table Vi Seasonal p r o b a b i l i t y of p o l l e n flow f o r Columbine and Indian paintbrush based on hummingbird f l i g h t d i s t a n c e s . Distance _{m}_ Columbine I n d i a n paintbrush 0-2 .28 .51 2-4 . 35 . 29 4-6 .24 . 08 6-8 .08 . 07 8-10 .04 . 02 10-12 .01 • 02 12-14 .01 P r o b a b i l i t i e s are based on p o l l e n c a r r y over to the tenth flower v i s i t e d and the f a c t t h a t a b i r d v i s i t s three columbine and seven Indian p a i n t b r u s h f l o w e r s per patch. 59 they remain on f l o w e r s f o r long p e r i o d s of time (up to an hour or more) before moving on, a l l of which w i l l reduce t h e i r e f f e c t i v e n e s s as p o l l i n a t o r s . Chase and Raven (1975) a l s o noted Syrphid v i s i t o r s to columbine. Two taxa o f i n s e c t v i s i t o r s are probably e f f e c t i v e p o l l i n a t o r s of Indian p a i n t b r u s h . The f i r s t and most f r e q u e n t l y observed was a l a r q e bee ( f a m i l y Megachilidae) and the other was a s m a l l s o l i t a r y bee ( f a m i l y H a l i c t i d a e ) . I n d i v i d u a l s of both types fed on nectar by probing head downward i n t o the tubes of f l o w e r s while o r i e n t e d so that t h e i r abdomens co n t a c t e d the anthers and stigma. The M e g a c h i l i d c a r r i e s p o l l e n i n a l a y e r of h a i r s on i t s abdomen and manipulates the anthers with i t s l e g s and abdomen while i n t h i s head downward p o s i t i o n , presumably c o l l e c t i n q p o l l e n . The H a l i c t i d s seemed t o gather p o l l e n with t h e i r hind l e g s i n a s i m i l a r manner although they l a c k the p o l l e n s t o r i n g abdominal h a i r s . P l a n t Breeding Systems Columbine f l o w e r s are c l e a r l y s e l f - c o m p a t i b l e , s i n c e t h e r e i s no s i g n i f i c a n t d i f f e r e n c e between the number of seeds s e t between s e l f e d or o u t c r o s s e d flowers (Table V I I ) . Even f l o w e r s from which i n s e c t s were excluded ( c l a s s 5) set good seed. During f l o r a l development of columbine the anthers mature w e l l ahead of the stiqmas, which mature at f l o w e r i n q staqe 6 ( F i g . 7); at t h i s p o i n t the s t y l e s protrude below the d r i e d up anthers and the l o b e s of the s t i q m a t i c s u r f a c e s open up. At t h i s stage the stigmas s t a i n e d with l a c t o p h e n o l c o t t o n b l u e , and the stigmas of 60 unbagged f l o w e r s were covered with p o l l e n g r a i n s t h a t showed evidence of p o l l e n tube growth, a l l o f which i n d i c a t e d t h a t the stigmas were r e c e p t i v e . I n d i a n paintbrush i s a p p a r e n t l y an o b l i g a t e l y o u t c r o s s i n g s p e c i e s , s i n c e very l i t t l e i f any seed was s e t u n l e s s the flowers were outcrossed (Table V I I I ) . My evidence concerning s t i g m a t i c maturity i n Indian paintbrush f l o w e r s i s somewhat c o n f l i c t i n g . The stigmas of f a i r l y s m a l l immature fl o w e r s ( f l o w e r i n g stage 2; F i g . 8) s t a i n e d with l a c t o p h e n o l c o t t o n blue as did those of l a t e r stages ( f l o w e r i n g stages 3-6; F i g . 8). There was no p o l l e n present on the stigmas of the immature f l o w e r s though, which lea d s me to question e i t h e r t h e i r r e c e p t i v i t y or the a p p l i c a b i l i t y of the l a c t o p h e n o l - c o t t o n blue t e s t i n t h i s case. The f i r s t anthers mature at f l o w e r i n g stage 4 which i s a l s o the stage where I can be c e r t a i n that the stigmas a r e mature ( p o l l e n g r a i n s and tubes are p r e s e n t ) . Thus, I can conclude t h a t these p l a n t s may be somewhat protogynous but f u r t h e r evidence concerning r e c e p t i v i t y of younger stigmas i s needed to prove t h i s p o i n t . 61 Table VII Seed s e t data f o r Columbine. Experiment Number Number of p l a n t s of f l o w e r s Mean number good seeds per capsule Flowers s e l f e d (with own pollen) Flowers s e l f e d (with p o l l e n from same plant) Outcrossed Emasculated then outcrossed Bagged only Emasculated only Wild c o n t r o l 12 10 9 6 11 4 16 23 22 21 14 17 10 16 13.4+1.49 14.5+1.53 14.1+1.53 8.0+1.01 14.1+1.12 1.6+0.88 23.6+1.19 1.39 NS 1.08 NS 1.19 NS 3.84 NS 1.19 NS 9. 59* * = s i g n i f i c a n t at P<,05 A l l experiments t e s t e d a g a i n s t w i l d c o n t r o l . 62 Table 1111 Seed set data for Indian paintbrush. Experiment Number Number Mean number good seeds of plants of flowers per capsule Flowers selfed (with own pollen) Flowers selfed (with pollen from same plant) Outcrossed Emasculated then outcrossed Bagged only Emasculated only Wild control 20 25 27 29 31 147 75 0. 10+0.10 0. 29*0.29 0.0 90.0*7. 10 44.87* 44.59* 110.4+8.78 1.03 NS * = s i g n i f i c a n t at P<.05 A l l experiments tested against wild control. 63 DISCUSSION i!2liis£ flow In the p r e v i o u s c h a p t e r s I d i s c u s s e d each of the components of t h i s system as separate e n t i t i e s . Here I w i l l d i s c u s s the dynamics of p o l l e n flow f o r t h i s system based on these components and the i n t e r a c t i o n s between them. I n i t i a l l y I set cut t o determine the i n f l u e n c e t e r r i t o r i a l boundaries have on p o l l e n flow. I hypothesized t h a t because t e r r i t o r i a l boundaries change r a p i d l y over time while the p l a n t s they encompass remain i n f l o w e r , the c o n s t r a i n t s on o u t c r o s s i n g proposed by Grant and Grant (1968) and L i n h a r t (1973) would be l e s s s e v e r e . I found, as those authors did, t h a t b i r d s c o n f i n e d the m a j o r i t y of t h e i r f o r a g i n g f l i g h t s t o t h e i r t e r r i t o r i e s (Table I I I ) . However, the s p a t i a l arrangement of the t e r r i t o r i e s changed f r e q u e n t l y and on as s h o r t a time s c a l e as p a r t o f a day ( F i g s . 3-6), and most of the p l a n t s remained i n f l o w e r throughout these changes. Each i n d i v i d u a l p l a n t i s surrounded by dynamically changing t e r r i t o r i a l boundaries which may enclose o r exclude d i f f e r e n t p l a n t s at d i f f e r e n t times i n the season, k g i v e n p l a n t w i l l u s u a l l y be w i t h i n some hummingbird's t e r r i t o r y , but because the t e r r i t o r i a l boundaries change, so w i l l the p l a n t s which are p o t e n t i a l p o l l e n sources. The p l a n t w i l l c o n t i n u e f l o w e r i n g throughout these changes and thus i t may be g i v i n g or r e c e i v i n g p o l l e n from a l a r g e r and d i f f e r e n t pool of p l a n t s than those enclosed by a p a r t i c u l a r t e r r i t o r y on a p a r t i c u l a r day. 64 On i n i t i a l c o n s i d e r a t i o n one might conclude that the breeding pool f o r a p a r t i c u l a r p l a n t i s d e l i m i t e d by the l a r g e s t t e r r i t o r y t h a t the p l a n t was i n . However, s i n c e the shapes of t e r r i t o r i a l boundaries are i r r e g u l a r the boundary of the breeding pool would be a composite o f the boundaries of a l l the t e r r i t o r i e s i n which a given p l a n t was i n c l u d e d . Within the breeding pool surrounded by t h i s composite boundary, the p r o b a b i l i t y of p o l l e n being t r a n s f e r r e d from one p l a n t to another i s a f u n c t i o n of the amount of time t h a t these two p l a n t s are e n c l o s e d by the same t e r r i t o r i a l boundaries ( F i g . 16). My r e s u l t s suggest t h a t p o l l e n does not move randomly throughout a t e r r i t o r y . I t i s necessary to c o n s i d e r c h a r a c t e r i s t i c s of a b i r d ' s f o r a g i n g behavior beyond the f a c t t h a t hummingbirds r e s t r i c t t h e i r v i s i t s to w i t h i n t e r r i t o r i a l boundaries. The key element i s the d i s t a n c e a b i r d f l i e s between the f l o w e r s i t v i s i t s . The majority o f f l i g h t s are from flower t o flower or i n f l o r e s c e n c e t o i n f l o r e s c e n c e w i t h i n patches. I f a patch i s equal t o a p l a n t , v i s i t s w i t h i n patches r e s u l t mainly i n s e l f p o l l i n a t i o n . Since a patch i s somewhat l a r g e r than a p l a n t (Table V) the amount of s e l f p o l l i n a t i o n may not be as g r e a t . The d i s t a n c e of c r o s s p o l l i n a t i o n s hould be determined by the d i s t a n c e flown between patches. Between patch f l i g h t d i s t a n c e s remain at about two meters r e g a r d l e s s of t e r r i t o r y s i z e ( F i g s . 9,10). T h i s s h o r t patch to patch f l i g h t d i s t a n c e i n combination with the extent o f w i t h i n patch v i s i t a t i o n f a v o r s p o l l e n d i s p e r s a l t o near neighbors. T h i s trend i s independent of t e r r i t o r y s i z e and there i s a high p r o b a b i l i t y of p o l l e n 65 F i g u r e 16: The e f f e c t s o f changes i n t e r r i t o r i a l boundaries on p o t e n t i a l p o l l e n flow f o r a p l a n t i n meadow 1. 1. P l a n t (x) surrounded by a s i n g l e t e r r i t o r y . 2. Composite of a l l the t e r r i t o r i e s which surrounded t h i s p l a n t d u r i n g the study. Shaded areas i n d i c a t e the l a r g e s t t e r r i t o r y t h a t t h i s p l a n t was i n . 3. The shading i n d i c a t e s the amount of time which p l a n t s were w i t h i n the same t e r r i t o r i a l boundaries as p l a n t x. Eg. P l a n t x was within the same boundary as A f o r 1 4% of the time, and pl a n t B f o r 57%. 67 movement at d i s t a n c e s c o n s i d e r a b l y s m a l l e r than a t e r r i t o r y . T h i s would reduce the i n f l u e n c e of t e r r i t o r y boundaries on p o l l e n flow. T h e i r major i n f l u e n c e would be near boundaries, where p o l l e n flow would be r e s t r i c t e d i n d i r e c t i o n because of the f a c t t h a t b i r d s seldom c r o s s boundaries when f o r a g i n g . My l a b o r a t o r y experiments i n d i c a t e t h a t p o l l e n i s t r a n s f e r r e d c o n s i d e r a b l y f u r t h e r than t h e f i r s t f lower v i s i t e d ; t h i s f a c t o r w i l l i n c r e a s e the proba.ba.bi.lity of p o l l e n flow a t gr e a t e r d i s t a n c e s (Table V I ) . Because the p o t e n t i a l p o l l e n flow d i s t a n c e i n c r e a s e s due to p o l l e n c a r r y over the i n f l u e n c e of t e r r i t o r i a l boundaries on p o l l e n flow w i l l be more pronounced than I i n d i c a t e d above. The composite p i c t u r e o f p o l l e n flow I get from i n t e r r e l a t i n g these components i s d e p i c t e d by F i g u r e s 17 and 18. The u n d e r l y i n g maps i n each F i g u r e d e p i c t p o l l e n flow p r o b a b i l i t i e s based only on the i n t e r a c t i o n s of changing t e r r i t o r i a l boundaries. The o v e r l a y s d e p i c t p o l l e n flow p r o b a b i l i t i e s based on hummingbird f l i g h t d i s t a n c e s (as mo d i f i e d by p o l l e n c a r r y o v e r ) . These p r o b a b i l i t i e s are based on f o r a g i n g f l i g h t d i s t a n c e s from data on a l l the f o r a g i n g f l i g h t s i n a meadow recorded d u r i n g the study (Table V I ) . Since l o c a l d i f f e r e n c e s i n topography and plant d e n s i t y may modify l o c a l d i s t r i b u t i o n of f o r a g i n g f l i g h t s , these data can only provide an approximation of the p r o b a b i l i t y of p o l l e n flow f o r an i n d i v i d u a l p l a n t . P o l l e n flow p r o b a b i l i t i e s which i n c o r p o r a t e the i n f l u e n c e of hummingbird f o r a g i n g f l i g h t d i s t a n c e s , an approximation of p o l l e n c a r r y over, and the e f f e c t of combined t e r r i t o r i a l 68 boundaries may be d e r i v e d by m u l t i p l y i n g the p r o b a b i l i t i e s based on each f a c t o r (from Figs.17 and 18) f o r a p l a n t at any p o i n t i n the meadow. Th i s i s assuming t h a t two p l a n t s are capable of p o l l e n t r a n s f e r and t h a t p r e v i o u s l y deposited p o l l e n has not alrea d y f e r t i l i z e d the ovule s . For example, p l a n t 1 (Fig.17a) would have a p r o b a b i l i t y o f .30 of exchanging p o l l e n with p l a n t x. Plant 2 would only have a .05 p r o b a b i l i t y . Even though the p r o b a b i l i t y of p o l l e n flow f o r both p l a n t s based on f o r a g i n g f l i g h t d i s t a n c e s i s q u i t e high{.35), the p r o b a b i l i t y of p o l l e n flow between p l a n t 2 and p l a n t x i s g r e a t l y reduced because plant 2 was w i t h i n the same t e r r i t o r i a l boundaries as plant x f o r only 14JS o f the study season. The o v e r a l l p o l l e n flow p r o b a b i l i t y between p l a n t x ( F i q . 17b) and p l a n t 3 i s .25 and between p l a n t x and p l a n t 4 i s .17. T h i s i n d i c a t e s how the high p r o b a b i l i t y of s h o r t d i s t a n c e f o r a g i n g f l i g h t s w i l l reduce p o l l e n flow d e s p i t e the high (.71) p o l l e n f l o w p r o b a b i l i t y based on t e r r i t o r i a l boundary l o c a t i o n . although the present data are im p r e c i s e f o r some l o c a l s i t u a t i o n s and i n d i v i d u a l p l a n t s , i t i s c l e a r t h a t p o l l e n flow f o r p l a n t s i n d i f f e r e n t areas o f a meadow i s q u i t e d i f f e r e n t due to the l o c a t i o n of t e r r i t o r i a l boundaries. Here again the i n f l u e n c e of l o c a l d i f f e r e n c e s i n topography and p l a n t d e n s i t y can be seen. The l o c a t i o n and s i z e of t e r r i t o r i e s i s i n f l u e n c e d by topography (e. g. rock outcrops which i n f l u e n c e where p l a n t s grow, perch l o c a t i o n s , e t c . ) , and p l a n t d e n s i t y (see c o r r e l a t i o n between p l a n t d e n s i t y and t e r r i t o r y s i z e i n Gass 1974, Gass et a l . 1976). Pl a n t x i n F i g . 17a was l o c a t e d at the edge of t e r r i t o r i e s throughout most of the study, thus the pool of l i r e 17: , D i a g r a m a t i c r e p r e s e n t a t i o n o f p o l l e n f l o w f o r two c o l u m b i n e p l a n t s i n meadow 1. I n s e t map i n d i c a t e s l o c a t i o n o f e a c h p l a n t . C i r c l e s i n d i c a t e i n t e r v a l s o f 2 m f r o m t h e p l a n t . Numbers i n d i c a t e t h e p r o b a b i l i t y o f a p l a n t b e i n g v i s i t e d a t t h a t d i s t a n c e b a s e d on p o l l e n c a r r y o v e r t o t h e t e n t h f l o w e r v i s i t e d ( T a b l e V I ) . S h a d i n g a s i n F i g . 1 6 . See t e x t f o r d i s c u s s i o n . J 72 Figure 13: Diagratnatic representation of pollen flow for two Indian paintbrush plants in meadow 2. Inset map indicates location of each plant. C i r c l e s indicate i n t e r v a l s of 2 m from the plant. Numbers indicate the p r o b a b i l i t y of a plant being v i s i t e d at that distance based on pollen carry over to the tenth flower v i s i t e d (Table VI). Shading as in Fig.16. See text for discussion. 4 - 5 m / c m 75 p o t e n t i a l sources f o r t h i s p l a n t changed c o n s i d e r a b l y with each change i n t e r r i t o r i a l boundaries. P l a n t x i n Pig.17b was l o c a t e d i n the middle of t e r r i t o r i e s and thus the members of i t s breeding pool d i d not vary much with t e r r i t o r i a l changes. In g e n e r a l , because of the freguency of changes i n t e r r i t o r i a l boundaries i n these meadows, t e r r i t o r y edge p l a n t s have the o p p o r t u n i t y f o r p o l l e n exchange between a wider range of p l a n t s than m i d - t e r r i t o r y p l a n t s . The dynamics o f t e r r i t o r i a l boundary changes i n a meadow w i l l produce a range from e x c l u s i v e l y "edge" p l a n t s t o e x c l u s i v e l y "middle" p l a n t s . The extent of d i v e r s i t y of breeding pools f o r these p l a n t s w i l l be governed by t h i s range. I have d e p i c t e d p o l l e n flow i n these meadows based cn f o u r f a c t o r s : 1) How long the p l a n t s are i n f l o w e r . 2) The d i s t a n c e between the p l a n t s . 3) How l o n g two p l a n t s are surrounded by the same t e r r i t o r i a l boundaries. 4) The number of p l a n t s (or flowers) which the b i r d v i s i t s b efore v i s i t i n g the second p l a n t i n c o n s i d e r a t i o n . Each f a c t o r alone w i l l not give an accurate p r e d i c t i o n of p o l l e n flow. P r o b a b i l i t i e s based on i n t e r r e l a t i n g these f o u r f a c t o r s p r ovide i n s i g h t i n t o o v e r a l l p o l l e n flow dynamics* However, they l a c k p r e c i s i o n i n t h e i r p r e d i c t i o n s s i n c e they do not account f o r the e f f e c t s of l o c a l v a r i a b i l i t y i n f o r a g i n g f l i g h t d i s t a n c e s . An important next step should be t o d e f i n e an index of t h i s v a r i a b i l i t y t o i n c o r p o r a t e i n these c a l c u l a t i o n s . Two other general problems must a l s o be s t u d i e d . F i r s t , a more 76 a c c u r a t e f i e l d measure of p o l l e n c a r r y over f o r both s p e c i e s i s needed. Second, the extent and importance of the i n f l u e n c e o f long perch to patch f l i g h t s on f o r a g i n g f l i g h t d i s t a n c e s must be assessed. The E f f e c t Of F l i g h t s To And From A Perch My data suggest t h a t the component of w i t h i n f l i g h t f o r a g i n g behavior t h a t i s most r e s p o n s i v e to changes i n t e r r i t o r y boundaries i s the d i s t a n c e a b i r d f l i e s t o a flower from a perch and to a perch from a f l o w e r . These perch-patch and patch-perch f l i g h t s c o u l d be g u i t e important i n determining o v e r a l l p o l l e n flow and degree of o u t c r o s s i n g . Unless a b i r d wipes i t s b i l l or preens e x c e s s i v e l y while perched (which, from my o b s e r v a t i o n s i s u s u a l l y not the case) the p o l l e n from the l a s t flower v i s i t e d on one f l i g h t should c a r r y over t o the f i r s t p l a n t v i s i t e d on the f o l l o w i n g f l i g h t . Although these l o n g e r f l i g h t s are on l y two components of an e n t i r e f o r a g i n g f l i g h t , they c o u l d s i g n i f i c a n t l y i n c r e a s e p o l l e n flow d i s t a n c e s . On the average a f o r a g i n g f l i g h t c o n s i s t e d of v i s i t s t o about three columbine or Indian p a i n t b r u s h patches (about e i g h t columbine f l o w e r s or 13 Indian paintbrush i n f l o r e s c e n c e s and 21 Indian paintbrush f l o w e r s ; T a b l e X; Appendix). Each average f l i g h t then, c o n s i s t e d of two long perch-patch f l i g h t s , t w o s h o r t (about 2 m) f l i g h t s between patches, and f i v e (columbine) or seven (Indian paintbrush) very s h o r t (about 10 cm) f l i g h t s between f l o w e r s or i n f l o r e s c e n c e s i n a patch. For Indian paintbrush t h e r e are an a d d i t i o n a l 12 very s h o r t moves between the f l o w e r s on i n f l o r e s c e n c e s . The c o n t r i b u t i o n of the lo n g e r 77 f l i g h t s t o p o t e n t i a l p o l l e n flow d i s t a n c e s would be 22% (2 of 9 t o t a l moves per f l i g h t ) f o r columbine and 8.7% <2 of 23 t o t a l moves) f o r Indian p a i n t b r u s h . I t i s i n t e r e s t i n g t o note that a l a r g e number of s i m u l t a n e o u s l y f l o w e r i n g flowers per p l a n t would decrease the p o t e n t i a l d i s t a n c e of p o l l e n flow, as can be seen by comparing the percentages f o r columbine and Indian paintbrush. The next step i n s t u d y i n g hummingbird mediated p o l l e n flow i n these meadows i s t o determine e x a c t l y what i n f l u e n c e the perch-patch f l i g h t s have on p o t e n t i a l p o l l e n flow d i s t a n c e s , by c a r e f u l l y r e c o r d i n g data on c o n s e c u t i v e f l i g h t s which are i n t e r u p t e d by p e r c h i n g . The presence of the long d i s t a n c e perch to patch f l i g h t s combined with the assumption t h a t p o l l e n c a r r y over c o n t i n u e s through at l e a s t the t e n t h flower v i s i t e d should i n c r e a s e c o n s i d e r a b l y the p r o b a b i l i t y of p o l l e n flow f o r longer d i s t a n c e s , p o s s i b l y approaching the point where e s s e n t i a l l y the only l i m i t on t h i s d i s t a n c e i s the t e r r i t o r y boundary i t s e l f . A major ques t i o n that needs to be answered, though, i s what the d i s t a n c e i s between the l a s t patch a b i r d v i s i t s before p e r c h i n g , and the f i r s t patch v i s i t e d on the next f l i g h t . I f the b i r d r e t u r n s on the next f l i g h t t o a patch near the one that ended the l a s t f l i g h t , these patch to perch f l i g h t s may have only a minor e f f e c t on p o l l e n flow d i s t a n c e . 78 P o l l e n Carry, Over The f u c h s i a flowers I used i n the l a b o r a t o r y experiments e x h i b i t the morphology of t y p i c a l hummingbird f l o w e r s ( P e r c i v a l 1965, F a e g r i and van der P i j l 1966, Grant 1966, P r o c t o r and Yeo 1972), but they are d i f f e r e n t i n many aspects from the two s p e c i e s I s t u d i e d i n the f i e l d . However, I b e l i e v e the general trends shown i n the l a b o r a t o r y experiments can be extended to p o l l e n c a r r y over f o r columbine and I n d i a n p a i n t b r u s h . I attempted some c r o s s i n g and p o l l e n c a r r y over experiments with Indian paintbrush i n the f i e l d u s ing a s t u f f e d hummingbird t o t r a n s f e r p o l l e n from a s i n g l e p o l l e n source to a number of " s i n k s " . Even a f t e r v i s i t i n g t e n p o l l e n s i n k s I c o u l d o f t e n see p o l l e n i n the f e a t h e r s of the s t u f f e d b i r d and on the stigmas of the p l a n t s . A l l f l o w e r s used i n these experiments had been bagged i n bud and t h e r e f o r e had not been p o l l i n a t e d . I observed very l a r g e amounts of p o l l e n on the b i r d s i n the f i e l d . The p o l l e n present was so c l e a r l y v i s i b l e t h a t i t c o u l d be used as temporary i d e n t i f y i n g marks f o r b i r d s f o r a g i n g on d i f f e r e n t s p e c i e s of f l o w e r s . The presence of these l a r g e amounts of p o l l e n i s a l s o i n d i c a t i v e o f a p o t e n t i a l c a p a c i t y f o r e x t e n s i v e p o l l e n c a r r y over. Because both columbine and f u c h s i a have p r o t r u d i n g anthers and stigmas, I f e e l that the v a r i a b i l i t y i n t h e way the hummingbirds co n t a c t e d the stigmas of the f u c h s i a f l o w e r s may occur f o r columbine as w e l l . The hidden r e p r o d u c t i v e p a r t s and t u b u l a r f l o w e r s of Indian p a i n t b r u s h make t h i s type of v a r i a b i l i t y i n f e e d i n g l e s s l i k e l y i n t h a t s p e c i e s . 79 L e v i n and Berube (1972) experimented with p o l l e n c a r r y over i n h e t e r o s p e c i f i c phlox p o l l e n c a r r i e d on the p r o b o s c i s o f Lepidopterans. In t h e i r work, p o l l e n c a r r i e d over to the f i f t h flower ( f o r Phlox p i l o s a p o l l e n on P. glaberrima stigmas) but most (about 45 g r a i n s ) of the p o l l e n l o a d was dep o s i t e d on t h e f i r s t f l o w e r and only three g r a i n s were deposited on the f i f t h f l ower v i s i t e d . For the r e c i p r o c a l c r o s s , p o l l e n only c a r r i e d over t o the t h i r d f l o w e r with a mean of 1.39 g r a i n s on the f i r s t and 0.17 on the t h i r d stigma. Thus p r o b a b i l i t y of p o l l e n flow past flower one i s q u i t e s m a l l i n that system. P o l l e n flow i s probably g r e a t e r i n p o l l i n a t i o n s between c o n s p e c i f i e s , s i n c e the f l o r a l mechanisms of these two s p e c i e s are not t o t a l l y compatible (Levin and Berube 1972). D i f f e r e n c e s i n behavior p a t t e r n s and g e n e r a l morphology between hummingbirds and i n s e c t s l e a d s me t o hypothesize that i n ge n e r a l , hummingbird mediated p o l l e n c a r r y over w i l l be c o n s i d e r a b l y g r e a t e r than i n s e c t mediated c a r r y over. P o l l e n l o a d s a v a i l a b l e f o r t r a n s f e r should be g r e a t e r f o r hummingbirds than i n s e c t p o l l i n a t o r s . The amount o f s u r f a c e area a v a i l a b l e t o c a r r y p o l l e n on a hummingbird's head, neck and b i l l i s g r e a t e r than an i n s e c t ' s p r o b o s c i s or the area of s u r f a c e h a i r s on the bodies of some i n s e c t p o l l i n a t o r s , although the p o l l e n c a r r y i n g s u r f a c e area of the l a r g e r bees may be comparable t o that of the hummingbirds. Since bees o f t e n c o l l e c t and s t o r e p o l l e n i n s p e c i a l i z e d h a i r s i n order t o p r o v i s i o n a nest or h i v e ( P e r c i v a l 1965, F a e g r i and van der P i j l 1966, P r o c t o r and Yeo 1972), much of t h i s p o l l e n i s e s s e n t i a l l y u n a v a i l a b l e f o r c a r r y over. In many cases the c o n t a c t of an i n s e c t p o l l i n a t o r with the 80 r e p r o d u c t i v e p a r t s of a flower may be more p r e c i s e than t h a t o f a hummingbird, s i n c e they o f t e n land on a flower and crawl over i t while f e e d i n g . T h i s would cause any p o l l e n a v a i l a b l e f o r t r a n s f e r on an i n s e c t to be depleted more r a p i d l y . The v a r i a b i l i t y i n s t i g m a t i c c o n t a c t which may occur when a hummingbird feeds would a l s o extend and i n c r e a s e the v a r i a b i l i t y i n the c a r r y over d i s t a n c e . In using emasculated f l o w e r s f o r the p o l l e n " s i n k s " I removed one f a c t o r which may be very r e l e v a n t to p o l l e n c a r r y over. Because of the l a c k of p o l l e n on emasculated f l o w e r s , I couldn't t e l l how the p o l l e n p i c k e d up at each fl o w e r a f f e c t s p o l l e n d i s p e r s a l from the "source" f l o w e r . T h i s masking c o u l d a f f e c t p o l l e n c a r r y over i n t h r e e ways. 1) I f p o l l e n from s u c c e s s i v e f l o w e r s was deposited on the b i r d i n l a y e r s , p o l l e n from the source f l o w e r would be bu r i e d under more r e c e n t l y deposited p o l l e n and would not be a v a i l a b l e f o r t r a n s f e r . 2) I f p o l l e n from each source was de p o s i t e d at random on the b i r d , p o l l e n from the source flower would be d i s t r i b u t e d f u r t h e r , but i n s m a l l e r q u a n t i t i e s t o each flower w i t h i n a mixture of p o l l e n from a l l of the flowers v i s i t e d . 3) I f p o l l e n from each source was deposited cn and t r a n s f e r r e d from d i f f e r e n t l o c a t i o n s on the b i r d , the source p o l l e n would be d i s t r i b u t e d as though there was no other p o l l e n present. An experiment u s i n g i n t a c t flowers and e i t h e r dyed p o l l e n or p o l l e n of another s p e c i e s as source p o l l e n would probably 81 provide some i n s i g h t i n t o how the i n t e r a c t i o n s of p o l l e n from s e v e r a l f l o w e r s w i l l a f f e c t p o l l e n c a r r y over. The e xperimental technique I used to determine p o l l e n c a r r y over i s not p e r f e c t . I t does g i v e a good i n d i c a t i o n of the extent of hummingbird mediated p o l l e n c a r r y over though. Much of the p r e v i o u s r e s e a r c h on p o l l i n a t o r mediated p o l l e n and gene flow has been weakened because the authors have not been able to i n t e g r a t e determinations of p o l l e n c a r r y over with t h e i r data. I f e e l t h a t the techniques I have used i n these experiments can be r e f i n e d and expanded to provide more answers to the p o l l e n c a r r y over questions f o r a l l types of p o l l i n a t o r s . I n s e c t P o l l i n a t o r s I t seemed c l e a r t h a t both major i n s e c t s p e c i e s v i s i t i n g I ndian p a i ntbrush c o u l d be e f f e c t i v e p o l l i n a t o r s , but they are probably r e s p o n s i b l e f o r much l e s s p o l l e n d i s p e r s a l than hummingbirds. .Unlike the hotaeothermic hummingbirds, these bees are o n l y a c t i v e f o r a few hours at midday (Table IX; Appendix). They were not seen f o r a g i n g when there was a wind, or a drop i n temperature, even t h a t caused by c l o u d cover i n the meadow. Bombus t h a t v i s i t e d columbine were common i n the meadows a t a wider range of temperatures than the v i s i t o r s to Indian pa i n t b r u s h . Bombus s p e c i e s are p a r t i a l l y homeothermic ( H e i n r i c h 1972) which allows them t o s u c c e s s f u l l y d i s p l a c e p o i k i l o t h e r m i c i n s e c t p o l l i n a t o r s at high a l t i t u d e s ( H e i n r i c h and Raven 1972, H e i n r i c h 1975), However t h e i r number was reduced somewhat i n c o o l or windy weather (casual observations) . 82 I can not draw any c l e a r c o n c l u s i o n s about the r e l a t i v e c o n t r i b u t i o n s of Bombus and hummingbirds to p o l l e n flow. E x c l u s i o n experiments, a l l o w i n g only bees t o v i s i t a group of flowers and comparing t h e i r seed s e t t o flo w e r s v i s i t e d by both hummingbirds and bees would p r o v i d e the needed data t o compare the i n f l u e n c e s of these two p o l l i n a t o r s . I found i t q u i t e easy to r e c o r d bee f o r a g i n g behavior using the same methods I used to record hummingbird f o r a g i n g . T h i s type of data would a l s o c o n t r i b u t e t o an understanding of the c o n t r i b u t i o n s t h a t bees are making to the movement of p o l l e n i n these meadows. The d i v e r s i t y of i n s e c t p o l l i n a t o r s p e c i e s and t h e i r behavior i s wide ( P e r c i v a l 1965, F a e g r i and van der P i j l 1966, Pr o c t o r and Yeo 1972). fts f a r as I know only Lepidopterans and v a r i o u s bee s p e c i e s have been s t u d i e d i n r e s e a r c h on the d i s t a n c e o f i n s e c t mediated p o l l e n flow (e. g. K e r s t e r and L e v i n 1968, L e v i n and K e r s t e r 1968, 1969a,b, 1974; B e a t t i e 1976). These i n v e s t i g a t o r s used i n s e c t f l i g h t d i s t a n c e s as i n d i c a t o r s of p o l l e n flow as I d i d i n t h i s study,and found t h a t i n gen e r a l f l i g h t d i s t a n c e s were s h o r t (Levin and K e r s t e r 1968,1969a,b, Ke r s t e r and L e v i n 1968, B e a t t i e 1976). The majority of the hummingbird f l i g h t s I noted were a l s o s h o r t , u n l i k e i n s e c t s , the hummingbirds e x h i b i t e d a high freguency of longer moves, the perch-patch f l i g h t s . These f l i g h t s , along with a p o s s i b l e g r e a t e r p o l l e n c a r r y over d i s t a n c e f o r hummingbirds l e a d s me to b e l i e v e t hat hummingbird mediated p o l l e n flow may extend over longer d i s t a n c e s than that observed f o r i n s e c t v i s i t o r s . 83 Pl§£t Density Host r e s e a r c h on i n s e c t mediated p o l l e n flow i n d i c a t e s t h a t p l a n t d e n s i t y and d i s t r i b u t i o n a f f e c t the length of p o l l i n a t o r f o r a g i n g f l i g h t s . As d e n s i t y i n c r e a s e s , f l i g h t d i s t a n c e s become s h o r t e r (Levin and K e r s t e r 1969a,b,1974; B e a t t i e 1976). I t i s c l e a r from other data t h a t p l a n t d e n s i t y and spacing a l s o i n f l u e n c e hummingbird behavior. In n o n - t e r r i t o r i a l b i r d s the evidence p o i n t s to a s i m i l a r i n f l u e n c e of d e n s i t y on p o l l e n d i s p e r s a l d i s t a n c e to that found f o r i n s e c t p o l l i n a t o r s . That i s , p o l l e n d i s p e r s a l d i s t a n c e seems to i n c r e a s e with a decrease i n p l a n t d e n s i t y ( L i n h a r t 1973, S c h l i s i n g and T u r p i n 1971). For t e r r i t o r i a l b i r d s the d e t e r m i n a t i o n of whether or not a b i r d s e t s up a t e r r i t o r y and what s i z e the t e r r i t o r y w i l l be, i s based to a l a r g e extent on p l a n t d e n s i t y (Gass 1974, Gass et a l . 1976, Carpenter and MacMillen 1976, Kodric-Brown and Brown 1978) . What i s not known i s how p l a n t d e n s i t y a f f e c t s hummingbird f l i g h t s w i t h i n t e r r i t o r i e s . I have very l i t t l e data c o r r e l a t i n g p l a n t d e n s i t y and hummingbird f l i g h t d i s t a n c e s f o r my study area. T o t a l flower counts f o r each meadow (a very rough i n d i c a t i o n of density) i n c r e a s e and then decrease dur i n g the season ( F i g s . 19-21; Appendix), and these changes i n flower numbers can be c o r r e l a t e d with changes i n s i z e and numbers o f t e r r i t o r i e s i n the meadows (as i n Gass (1974) and Gass jet a l . (1976)). My data i n d i c a t e t h a t the perch-patch f l i g h t d i s t a n c e i s c o r r e l a t e d with t e r r i t o r y s i z e (thus a t l e a s t i n d i r e c t l y with p l a n t d e n s i t y ) , w h ile the i n t e r - p a t c h f l i g h t d i s t a n c e s remain 84 f a i r l y constant r e g a r d l e s s of changes i n t e r r i t o r y s i z e (and pla n t d e n s i t y ) . My data do not i n d i c a t e t h a t the r e l a t i o n s h i p between p l a n t d e n s i t y and hummingbird f l i g h t d i s t a n c e s w i t h i n t e r r i t o r i e s i s merely the simple i n v e r s e r e l a t i o n s h i p t h a t i s seen i n i n s e c t s . I t i n d i c a t e s a higher l e v e l of complexity i n t h i s r e l a t i o n s h i p which needs f u r t h e r i n v e s t i g a t i o n . Gene Flow P o l l e n flow, being the major means of g e n e t i c exchange f o r f l o w e r i n g p l a n t s , has o f t e n been used as an i n d i c a t o r o f gene flow i n plant p o p u l a t i o n s . The gen e r a l p r e d i c t i o n f o r r e s e a r c h both on i n s e c t and wind mediated p o l l e n d i s p e r s a l i s t h a t most o u t c r o s s i n g occurs only over very s h o r t d i s t a n c e s , even though both d i s p e r s a l agents o c c a s i o n a l l y move p o l l e n over long d i s t a n c e s , (e. g. Bateman 1947a,b; K e r s t e r and L e v i n 1968,Levin and K e r s t e r 1969a,b, Gleaves 1973, B e a t t i e 1976). My data p r e d i c t a high p r o b a b i l i t y o f short d i s t a n c e p o l l e n d i s p e r s a l i n a hummingbird p o l l i n a t i o n system which would l e a d to gene flow r e s t r i c t i o n i n t h e pl a n t p o p u l a t i o n s . In comparison to wind and i n s e c t s as p o l l i n a t o r s though, there may be a g r e a t e r p r o p o r t i o n of longer d i s t a n c e p o l l e n moves which should i n c r e a s e gene flow. The e f f e c t of hummingbird mediated p o l l e n flow on the movement of genes d i f f e r s between the two p l a n t s p e c i e s I s t u d i e d . Columbine i s a s e l f compatible s p e c i e s (Table V I I ) . Thus gene flow i n the columbine p o p u l a t i o n should be r e s t r i c t e d and c o n s i d e r a b l e i n b r e e d i n g c o u l d occur. The f a c t t h a t the 85 stigmas of f l o w e r s mature a f t e r the anthers have l o s t most of t h e i r p o l l e n reduces t h i s i n b r e e d i n g f a c t o r somewhat, but because more than one flower on a p l a n t i s l i k e l y t o be i n flower at one time the importance of t h i s r e d u c t i o n i s probably minimal. The p o t e n t i a l f o r s e l f p o l l i n a t i o n f o r I n d i a n p a i n t b r u s h i s even higher than t h a t f o r columbine. T h i s i s due to the f a c t t h a t a b i r d v i s i t s s e v e r a l f l o w e r s on each i n f l o r e s c e n c e and a s e v e r a l i n f l o r e s c e n c e s on each p l a n t before f l y i n g to the next p l a n t . In my study b i r d s v i s i t e d more than seven Indian paintbrush flowers per patch as compared to three columbine f l o w e r s . However, because Indian paintbrush i s s e l f i n c o mpatible, the p o t e n t i a l f o r i n b r e e d i n g i s not g r e a t . F u r t h e r i n v e s t i g a t i o n of the r e l a t i o n s h i p between hummingbird mediated p o l l e n flow and gene flow must i n c l u d e a more p r e c i s e determination o f t h e g e n e t i c s t r u c t u r e of the p l a n t p o p u l a t i o n s i n v o l v e d . The u t i l i z a t i o n o f g e n e t i c markers t o monitor a c t u a l gene flow i n a p l a n t p o p u l a t i o n should provide a good t e s t of the hypotheses d e r i v e d from knowledge of p o l l e n flow dynamics. 86 I m p l i c a t i o n s For Other Hummingbird P o l l i n a t i o n Systems Grant and Grant (1968) and L i n h a r t (1973) both concluded that hummingbird t e r r i t o r i a l behavior r e s t r i c t s p o l l e n flow and c o n t r i b u t e s t o i n b r e e d i n g i n p l a n t p o p u l a t i o n s . I have found t h a t the major r e s t r i c t i o n of p o l l e n flow i n my study area i s due not to t e r r i t o r i a l behavior but t o the predominance o f s h o r t f l i g h t s w i t h i n f o r a g i n g f l i g h t s . I n d i v i d u a l t e r r i t o r i e s are not powerful as r e s t r i c t i n g mechanisms because of numerous changes i n shape, s i z e , and p o s i t i o n i n g of the t e r r i t o r i e s surrounding a p l a n t which occur throughout i t s f l o w e r i n g season. They a l s o l o s e s i g n i f i c a n c e i n terms of i n h i b i t i n g p o l l e n flow because the sho r t f l i g h t d i s t a n c e s w i l l cause high p o l l e n flow w i t h i n even the s m a l l e s t t e r r i t o r i e s . Data on p o l l e n c a r r y over and long perch-patch f l i g h t s i n d i c a t e t h a t the low p r o b a b i l i t y of longer d i s t a n c e p o l l e n flow based on these s h o r t f l i g h t s may r e s u l t i n a f a i r l y l a r g e underestimate of a c t u a l p o l l e n flow d i s t a n c e s i n the p o p u l a t i o n . The power o f t e r r i t o r i a l boundaries as p o l l e n flow r e s t r i c t i n g mechanisms w i l l i n c r e a s e as the p o t e n t i a l p o l l e n flow d i s t a n c e w i t h i n the t e r r i t o r i e s i n c r e a s e s ( i n l i g h t of p o l l e n c a r r y over and l o n g f l i g h t s between a perch and a patch of f l o w e r s ) . ft l a r g e v a r i e t y of p l a n t s p e c i e s are v i s i t e d and p o l l i n a t e d by hummingbirds, (Grant and Grant 1966, S t i l e s and flolf 1970, S t i l e s 1975, Gass et a l . 1976, and o t h e r s ) , and the a p p l i c a b i l i t y of my r e s u l t s to other hummingbird p o l l i n a t i o n systems w i l l be a f f e c t e d by t h i s v a r i e t y . My c o n c l u s i o n s should apply f o r many other p e r e n n i a l herb p o p u l a t i o n s i n which the 87 p l a n t s remain i n f l o w e r f o r a s i m i l a r l y long time. I f the p l a n t s flower f o r a very r e s t i c t e d time the t e r r i t o r i a l boundary r e s t r i c t i o n on p o l l e n flow w i l l be much g r e a t e r , p o s s i b l y c o n t r i b u t i n g t o i n c r e a s e d i n b r e e d i n g f o r the p o p u l a t i o n . Of course gene flow w i l l be i n f l u e n c e d by the breeding system and means of seed d i s p e r s a l f o r each p l a n t s p e c i e s . P o l l e n and gene flow f o r a f l o w e r i n g t r e e or shrub, such as the t r e e (Genipa americana (Hubiaceae) ) s t u d i e d by S t i l e s and Wolf (1970), may d i f f e r e x t e n s i v e l y from that p o r t r a y e d f o r t h i s meadow. I n t h a t type of system the number of flo w e r s per pl a n t i s much l a r g e r than i n a s m a l l p e r e n n i a l herb, thus i t seems t h a t the r e s t r i c t i o n of p o l l e n flow between p l a n t s would be much g r e a t e r . I t would be i n t e r e s t i n g t o compare p o l l e n flow i n t h i s m i g r a t i n g hummingbird system t o t h a t of breeding hummingbirds. Breeding t e r r i t o r i e s may be held longer than the feed i n g t e r r i t o r i e s h e l d by migrants. T h i s would imply a s t r i c t e r c o n t r o l of p o l l e n flow imposed by the boundaries of a s i n g l e t e r r i t o r y . I t seems th a t here, as with a system i n which i n d i v i d u a l p l a n t s flower o n l y f o r a sh o r t p e r i o d of time, there would be a r e s t r i c t i o n of p o l l e n flow which may c o n s i d e r a b l y i n c r e a s e i n b r e e d i n g i n the p o p u l a t i o n . What d i f f e r e n c e s would be caused by s t r o n g versus weakly defended t e r r i t o r i e s ? I noted few f l i g h t s by i n t r u d e r s i n t c the t e r r i t o r i e s I observed, but Gass (1974) noted times of high r a t e s o f i n t r u s i o n at c e r t a i n times of day i n some t e r r i t o r i e s f o r the same meadows. L i n h a r t (1973) found p o l l e n movement a t a d i s t a n c e of 100 m from weakly defended t e r r i t o r i e s where he noted v i s i t s by i n t r u d i n g b i r d s . Wolf and S t i l e s (1970) and Wolf 88 (1975b) noted male hummingbirds a l l o w i n g females to feed i n t h e i r t e r r i t o r i e s during t h e breeding season,, I t would be i n t e r e s t i n g t o see how much these " i n t r u d e r s " 1 extend p o l l e n flow. What are the d i f f e r e n c e s i n p o l l e n f l o w between t e r r i t o r i a l and n o n - t e r r i t o r i a l s i t u a t i o n s ? I t has been shown t h a t t e r r i t o r i e s r e s t r i c t p o l l e n flow more than n o n - t e r r i t o r i a l s i t u a t i o n s ( L i n h a r t 1973, S c h l i s i n g and T u r p i n 1971, present s t u d y ) . Does t h i s a l s o imply t h a t f l o w e r s p o l l i n a t e d at the b e g i n i n g or end of a season, when ,the low numbers of flowers i n an area prevent the establishment o f t e r r i t o r i e s , and when any e x i s t i n g t e r r i t o r i e s occupy most of each meadow, w i l l r e c e i v e more " o u t c r o s s e d " p o l l e n and thus produce o f f s p r i n g with g r e a t e r v a r i a b i l i t y than those which are p o l l i n a t e d d u r i n g the peak of the f l o w e r i n g season? I f so what are the i m p l i c a t i o n s about gene flow i n these p o p u l a t i o n s ? I f c o m p e t i t i o n i s g r e a t , would the seeds s e t a t the beginning and end o f a f l o w e r i n g season have a higher p r o b a b i l i t y of growth and establishment than the seeds produced i n the middle of t h e season? I hope t h a t t h i s study w i l l provide a good s t a r t i n g p o i n t f o r working on the answers to some of these q u e s t i o n s . 89 LITERATURE CITED Alexopoulos,C.J., and E.S.Beneke. 1952. Laboratory Manual f o r I n t r o d u c t o r y Mycology. Burgess P u b l i s h i n g Co.,Minn., Minn. Armitage,K.B. 1955. T e r r i t o r i a l behavior i n f a l l migrant rufous hummingbirds. Condor 57:239-240. Bateman,A.J. 1947a. Contamination i n seed crops. I . I n s e c t p o l l i n a t i o n . J . G e n e t i c s 48:257-275. , Bateman,A.J. 1947b. Contamination i n seed c r o p s . I I I . R e l a t i o n with i s o l a t i o n d i s t a n c e . H e r e d i t y 1:303-336. Bene,?. 1945. 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E n e r g e t i c s of p o l l i n a t i o n . Annual Review of E c o l . and Syst. 6:139-170. He i n r i c h , B . , and P.H. Raven. 1972. E n e r g e t i c s and p o l l i n a t i o n ecology. Science 176:597-602. Heithaus,E.R. 1974. The r o l e of p l a n t - p o l l i n a t o r i n t e r a c t i o n s i n determining community s t r u c t u r e . Ann. Mo. Bot. Gard. 61 (3) :675-691. Kerster,H.W., and D. A. L e v i n . 1968. Neighborhood s i z e i n L i t Oospermurn ca r o l i n i e n s e . G e n e t i c s 60:577-587. 91 Kobbe,W.H. 1900. The rufous hummingbird of Cape Disappointment., Auk 17:8-15. Knuth,P. 1908. Handbook of flower p o l l i n a t i o n v o l . 2 . Clarendon Press, Oxford. Kodric-Brown,A., and J.H. Brown. 1978. I n f l u e n c e of economics, i n t e r s p e c i f i c c o m p e t i t i o n , and s e x u a l dimorphism of t e r r i t o r i a l i t y o f migrant rufous hummingbirds. Ecology {in press) . Levin,D.A. 1969. The e f f e c t o f c o r o l l a c o l o r and o u t l i n e on i n t e r s p e c i f i c p o l l e n flow i n Phlox. E v o l u t i o n 23:144-455. Levin,D.A,, and W.H. Anderson. 1970. Competition f o r p o l l i n a t o r s between simulaneously f l o w e r i n g s p e c i e s . Amer. Natur. 104:455-467. Levin,D.A., and D.E. Berube. 1972. Phlox and C o l i a s : The e f f e c i e n c y of a p o l l i n a t i o n system. E v o l u t i o n 26:242-250. Levin,D.A., and H.W. K e r s t e r . 1968. L o c a l gene d i s p e r s a l i n Phlox. E v o l u t i o n 22:130-139. Levin,D.A., and H.W. K e r s t e r . 1969a. Density-dependent gene d i s p e r s a l i n L i a t r i s . Amer. Natur. 103:61-73. Levin,D.A., and H.W. K e r s t e r . 1969b. The dependence of bee mediated p o l l e n and gene d i s p e r s a l on p l a n t d e n s i t y . E v o l u t i o n 23:560-572. Levin,D.A. and H.W. K e r s t e r . 1974. Gene flow i n seed p l a n t s . E v o l . B i o l . 7:139-220. levin,D.A., and H.W. K e r s t e r and M. N e i d z l e k . 1971. P o l l i n a t o r f l i g h t d i r e c t i o n a l i t y and i t s e f f e c t on p o l l e n flow. E v o l u t i o n 25:113-118. Linhart,Y.B. 1973. E c o l o g i c a l and b e h a v i o r a l determinants of p o l l e n d i s p e r s a l i n hummingbird p o l l i n a t e d H e l j c o n i a . Amer. Natur. 107 (956):511-523. Macior,L.W. 1966. Foraging behavior of Bombus (Hymenoptera: Apidae) i n r e l a t i o n t o A j u i l e g i a p o l l i n a t i o n . Amer. J . Bot. 53:302-309. Macior,!.W. 1971. C o - e v o l u t i o n of p l a n t s and an i m a l s - s y s t e m a t i c i n s i g h t s from p l a n t - i n s e c t i n t e r a c t i o n s . Taxon 20{1): 17-28. Macior,L.W. 1974. B e h a v i o r a l aspects of coadaption between f l o w e r s and i n s e c t p o l l i n a t o r s . Ann. Mo. Bot. Gard. 61(3): 760-769. 92 Mosguin,T. 1971. Competition f o r p o l l i n a t o r s as a s t i m u l u s f o r the e v o l u t i o n of f l o w e r i n g time. Oikos 22:398-40 2. Pe r c i v a l , M . 1965. F l o r a l b i o l o g y . Pergamon Press L t d . , Oxford. Pickens,A. L. 1944. Seasonal t e r r i t o r y s t u d i e s o f r u b y - t h r o a t s . Auk 61:88-92. P i t e l k a , F . A . 1942. T e r r i t o r i a l i t y and r e l a t e d problems i n North American hummingbirds. Condor 44:189-204., P h i l l i p s , A.R. 1975, The migrations of a l i e n ' s and other hummingbirds. Condor 77 (2) : 196-205. P r o c t o r , a . , and P.Yeo. 1972. The p o l l i n a t i o n of f l o w e r s . T a p l i n g e r P u b l i s h i n g Co., New York. Sass,J.E. 1958. B o t a n i c a l microtechnigue, 3rd ed. The Iowa S t a t e C o l l e g e Press, Ames, Iowa. Schemske,D.W. 1975. Time budget and f o r a g i n g s i t e p reference o f the cinnamon hummingbird i n Costa R i c a . Condor 77(2) :216-217. , Sc h l i s i n g , H . A , , and R.A. T u r p i n . 1971. Hummingbird d i s p e r s a l of Delphinium c a r d i n a l e p o l l e n t r e a t e d with r a d i o a c t i v e i o d i n e . Amer. J . Bot. 58:401-406. Stebbins,G.L.,Jr. 1950. V a r i a t i o n and e v o l u t i o n i n p l a n t s . Columbia U n i v e r s i t y P r e s s , New York and London. S t i l e s , F . G . 1971. Time, energy, and t e r r i t o r i a l i t y o f the anna hummingbird (Calypte anna). Science 173: 818-821. S t i l e s , F . G . 1975. Ecology, f l o w e r i n g phenology, and hummingbird p o l l i n a t i o n of some Costa Rican H e l i c o n i a s p e c i e s . Ecology 56(2) :285-301. S t i l e s , F . G . , and L.L. Wolf, 1970. Hummingbird t e r r i t o r i a l i t y a t a t r o p i c a l f l o w e r i n g t r e e . Auk 87:467-491. Van der P i j l , L . 1960. E c o l o g i c a l aspects of fl o w e r e v o l u t i o n . I. P h y l e t i c e v o l u t i o n . E v o l u t i o n 14:403-416. Van der P i j l , L . 1961. E c o l o g i c a l a s p e c t s o f flower e v o l u t i o n . I I . Zoophilous flower c l a s s e s . E v o l u t i o n 15:44-59. Wolf,L.L. 1969. Female t e r r i t o r i a l i t y i n a t r o p i c a l hummingbird. Auk 86:490-504. 93 Wolf,L.L., 1970. The impact o f s e a s o n a l f l o w e r i n g regimes on the b i o l o g y of some t r o p i c a l hummingbirds. Condor 72:1-11. Wolf/L.L. 1975a. Female t e r r i t o r i a l i t y i n the p u r p l e - t h r o a t e d c a r i b . auk 92:511-522. Wolf/L.L. 1975b. " P r o s t i t u t i o n " behavior i n a t r o p i c a l hummingbird. Condor 77(2):140-14 4. Wolf,L.L., and F.R. Hainsworth. 1971, Time and energy budgets of t e r r i t o r i a l hummingbirds. Ecology 52: 980-988. Wolf,L.L., F.R. Hainsworth and F.G. S t i l e s . 1972. E n e r g e t i c s of f o r a g i n g : Rate and e f f i c i e n c y of nectar e x t r a c t i o n by hummingbirds. Science 176: 1351-1352. Wolf,L.L., and F.G. S t i l e s . 1970. E v o l u t i o n o f p a i r c o o p e r a t i o n i n a t r o p i c a l hummingbird. E v o l u t i o n 24: 759-773. APPENDIX 95 Iable IX Times of i n s e c t v i s i t o r a c t i v i t y . Meadow 1 J4 Aug 1975 Time I n s e c t v i s i t o r s Counted 6:40 AM 0 9: 40 8 Bombus 11:36 9 Bombus 1:36 PM 3 Bombus 3:36 1 Bombus 1 Syrphidae 5:36 1 Bombus 2 Syrphidae Meadow 2 J15 A ug. 1975 Time Inse c t v i s i t o r s counted 6:30 AM 0 8:30 2 Megachilidae 10:30 9 Meg a c h i l i d a e 2 H a l i c t i d a e 12:30 PM 4 Megachilidae 3 H a l i c t i d a e 1 Bombus 2:30 8 Megachilidae 5 H a l i c t i d a e 4:30 0 ( E n t i r e meadow i n shade at about 4:00 PM) 6:30 0 96 Table X Number o f patches, flowers and i n f l o r e s c e n c e s (Indian paintbrush) v i s i t e d i n a f l i g h t . Mean number Mean number Mean number of patches of flowers of i n f l o r e s c e n c e s Columbine 2.9*0. 13 (203) 8.6 + 0.56 (154) Indian 2.9*0. 15 (81) 21.0+2.27(67) 9.6+0.98(63) Pa i n t b r u s h Numbers i n parentheses i n d i c a t e sample s i z e . 97 F i g u r e 19: Changes i n the number of columbine f l o w e r s fx) and Indian p a i n t b r u s h i n f l o r e s c e n c e s ( o ) i n meadow 1. 98 99 Figure 20: Changes in number of columbine flowers i n meadow 2. 100 101 F i g u r e 21: Changes i n the number of I n d i a n p a i n t b r u s h i n f l o r e s c e n c e s i n meadow 2. 102 6000 ^ 5000 1 4000 1 3000 1 S000 1 1000 1 26 29 '1 4 7 10 13 16 19 2 2 - 2 5 1975 J U L Y H A T F A U G 

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