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Character displacement and variability in lacustrine sympatric and allopatric Dolly Varden (Salvelinus malma) populations Armitage, Godfrey Norman

Abstract

The object of this study was to investigate character displacement (Brown and Wilson, 1956) and reduction of phenotypic variability with reduction in niche width (Van Valen, 1965). Dolly Varden from one sympatric (Loon Lake) and two allopatric (Dickson and Foley Lake) populations were compared. Field studies showed that the niche width of sympatric Dolly Varden was less than that of allopatric Dolly Varden owing to food and spatial segregation, confirming results of an earlier study (Andrusak and Northcote, 1971). Character displacement was evident in pyloric caeca numbers and in certain behavioural responses (spatial distribution and feeding) observed in the laboratory. These were accompanied by reduced variability, also apparent in length distributions within year classes, in the sympatric population compared with an allopatric population (Dickson Lake). However, character displacement and reduced variability could not be demonstrated for most morphometric characters, presumably because of the complexity of growth processes involved. Effects of overlapping adjacent year classes and of continuous growth of fish body parts (in contrast to comparable studies with birds) obscured interpretation of such characteristics.

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