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Population differentiation and conservation of song sparrows (Melospiza melodia) in the San Francisco Bay Area region inferred by morphological and microsattelite loci analysis

University of British Columbia

In this study I examined geographic variation in morphology and genetic population structure in five putative subspecies of song sparrows (Melospiza melodia) in the San Francisco Bay region (M. m. samuelis, M. m. maxillaris, M. m. pusillula, M. m. gouldii, and M. m. heermanni). My first goal was to describe genetic population structure at microsatellite loci to assist with conservation and management strategies for song sparrow populations in the San Francisco Bay Area. I sampled nine populations from five putative subspecies and found low estimates of differentiation between populations within subspecies (Fst analog: Φsc = 0.0122, p<0.0001, Rst analog Φsc = 0.00433, p=0.05963) and between subspecies (Fst analog: Φct = 0.0137, p = 0.04985, Rst analog Φct = 0.0174, p=0.09873) at microsatellite loci. Despite low estimates of divergence, genetic structure at the subspecies level was indicated by the larger amount of variance accounted for by subspecies than populations. I propose a Management Unit (MU) consisting of the range of M. m. pusillula be prioritized for conservation efforts based on the larger extent of genetic divergence shown by Cavalli-Sforza and Edward's chord distance and topology of the unweighted pair group cluster analysis which displayed 100% support of bootstrap replicates across loci. Additionally, I propose the ranges of M. m. samuelis and M. m. maxillaris be designated an M U despite low differentiation from M. m. heermanni, because it remains possible that adaptive differences between these types were not identified with neutral loci. The second goal of this study was to compare morphological and genetic estimates of divergence in order to evaluate previous hypotheses proposed for differentiation. Fourteen populations were included in a multivariate analysis of morphological traits and compared with the genetic differentiation derived from microsatellite loci analysis in Chapter 1. In contrast to the low genetic differentiation at microsatellite loci, morphological differentiation was high between song sparrow subspecies. Due to the lack of concordance between estimates of morphological and genetic divergence, selection or phenotypic plasticity in morphology are implicated as causes for morphological differentiation among song sparrow subspecies. It is probable that song sparrow subspecies in the San Francisco Bay region are recently diverged or have high current gene flow and, therefore, that the rate of evolution at morphological traits (assuming a heritable basis for those traits) is faster than at neutral loci.

Thesis/Dissertation

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2009-07-23

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http://hdl.handle.net/2429/11222

Forestry

University of British Columbia

UBCV

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