Morphometrics of trophic osteology in the threespine stickleback, Gasterosteus aculeatus

Landmark-based geometric morphometrics is used to detect interpopulation variation in skull morphology among samples from four populations representing anadromous, stream, and lacustrine planktivorous and benthic-feeding populations of threespine stickleback (Gasterosteus aculeatus) and between sexes within each population. Morphological differences among all four populations and between males and females are highly significant, although sexual dimorphism is primarily due to differences between the sexes in the stream population. The female stream and lacustrine benthic-feeding phenotypes are qualitatively and statistically indistinguishable. The anadromous phenotype is intermediate between lacustrine benthic and planktivorous phenotypes. Differences between samples are interpreted with reference to ecomorphological and functional morphological models.