This study will examine patterns of variation in body form among populations of an endemic radiation of threespine stickleback from Cook Inlet, Alaska to test current models of phenotypic evolution. Stickleback along the west coast of North America are of interest to the evolutionary biologist because of the recent (<22,000 years) colonization of diverse freshwater habitats from a marine ancestral population and subsequent differentiation of trophic and locomotor morphology among the populations. Body form will be measured using two-dimensional (x,y) coordinates of anatomical landmarks that permit the use of the most powerful methods available to describe and analyze shape. Three hypotheses of a functional integration model will be tested: 1) patterns of genetic and phenotypic correlations reflect functional integration (i.e. suites of characters that function in concert should have higher correlations than functionally unrelated characters). 2) patterns of phenotypic correlation are similar among populations. 3) interlocality and intralocality patterns of phenotypic correlations are similar. Biomechanical models and trophic and locomotor performance measures will be used to construct a priori hypotheses to test for functional integration. It is anticipated that results from this study will provide some of the critical empirical data necessary to resolve conflicting hypotheses on the role of constraints influencing phenotypic divergence among closely related populations.
