Divergence of cranial phenotypes among threespine stickleback populations

Characterizing phenotypic divergence using three-dimensional geometric morphometrics in four populations of threespine
(Gasterosteus aculeatus; Pisces: Gasterosteidae) in Katmai National Park and Preserve, Alaska
A.E. Pistore, T.N. Barry, E. Bowles, R. Sharma, S.L. Vanderzwan, S.M. Rogers, and H.A. Jamniczky


stickleback_comp Alex Pistore and authors (University of Calgary) test the hypothesis that stickleback populations inhabiting differing freshwater environments display cranial phenotypes that are intermediate between the ancestral marine form and the low-plated freshwater populations. Using using microcomputed tomography and three-dimensional geometric morphometrics, they report significant phenotypic differences among all four Alaska lake populations examined, including a component of sexual dimorphism. The authors also report evidence of disrupted phenotypic covariance structure among these populations, and suggest this may indicate the presence of disruptive selection acting to produce different optimal phenotypes under slightly different environmental conditions. Such phenotypic quantification is a key step in elucidating both the ecological processes responsible for rapid adaptive radiations and the role of developmental mechanisms in biasing evolutionary change.