PARENT SESSION
Contributed Oral Session 78: Evolutionary Ecology: Genetics
Wednesday, August 10, 8:00 AM - 11:30 AM, Meeting Room 516 D, Level 5, Palais des congrès de Montréal
Alternative ecological environments and gene flow influence morphological divergence in threespine stickleback.
Turcotte, Martin*,1, Moore, Jean-Sebastien1, Taylor, Eric2, Hendry, Andrew1, 1 McGill University, Montreal, Quebec2 University of British Columbia, Vancouver, Bristish Columbia
ABSTRACT- Alternative ecological environments can lead to divergent selection, which can drive adaptive divergence. At the same time, dispersal between populations should oppose natural selection and hamper adaptive divergence. We here consider the relative roles of gene flow and selection in nature by examining covariation among morphological divergence, gene flow and habitat differences at several spatial scales. Specifically, we examined morphological variation within and between seven watersheds where lake and stream populations of threespine stickleback (Gasterosteus aculeatus) occur in parapatry. We also examined variation along a stream within one of these systems. We estimated morphological divergence using geometric morphometrics and gene flow using DNA microsatellites. At each study site, we also quantified habitat features that should influence divergent selection. We found substantial morphological divergence between lake and stream populations within some watersheds. Some of this variation was correlated with habitat features, particularly water flow, suggesting an important role for natural selection in shaping morphology. However, the degree of morphological divergence between parapatric lake and stream populations differed among watersheds: divergence was positively correlated habitat differences but negatively correlated with gene flow. We also quantified shared (across watersheds) and unique (specific to watersheds) features of evolutionary diversification between lake and stream stickleback. We found strong evidence for the parallel morphological evolution of parapatric lake/stream populations across multiple watersheds, particularly with respect to body depth, but we also find a signature of unique divergence specific to individual watersheds. Both natural selection and gene flow appear to play critical roles in determining patterns of morphological variation among conspecific populations.
Key words: Morphological divergence, Geometric morphometrics, Gene flow, Stickleback