Meeting Abstract
Threespine stickleback (Gasterosteus aculeatus) have been shown to exhibit rapid, parallel changes in armour phenotype when adapting to new habitats, including substantial reduction in plate number in association with adaptation to freshwater environments. Such skeletal changes may occur in response to ecological variables including predation pressure and foraging mode, and environmental variables including mineral availability. Here, we test the hypothesis that changes in plate number are accompanied by changes in plate shape, extent of body coverage, and bone mineral density, reflecting a complex phenotypic response to different selective pressures in changing habitats. We predict that fish inhabiting tidally-influenced freshwater habitats will exhibit increased variation in plate phenotypes present, and that these phenotypes will collectively represent decreased investment in bone production. We use 2D and 3D imaging techniques to quantify a series of armour traits from stickleback occupying three marine habitats and one tidally-influenced freshwater stream in southwestern British Columbia. We find that stickleback inhabiting marine environments share a relatively conserved plate phenotype that includes a full complement of highly mineralized plates that provide extensive body coverage, while those inhabiting a stream environment express a plate phenotype that varies markedly on all axes measured both within this population and in comparison to their marine neighbours. Our results suggest that environmental chemistry may play a role in modulating how stickleback phenotypes change in response to new environments, and further hint at an important role for development in structuring phenotypic variation during the process of adaptive change in stickleback.
