Meeting Abstract
Adaptive radiations offer unique insights into evolutionary processes and elucidating the processes by which the evolution of new species occur. Parallelism in adaptive radiations could be the result of selection acting on standing genetic variation or via a ‘flexible stem system’ that causes the expression of consistently different phenotypes in different environments. Subsequent selection could produce ecotypic differences in adaptive radiations and thus the high levels of parallelism in these radiations. Evaluation of these alternatives is difficult, as comparison of ancestral genetic architecture or patterns of plasticity with those of derived, divergent ecotypes is rarely possible – primarily because the ancestral form is rarely extant. Using the threespine stickleback adaptive radiation, we employ a common-garden design and geometric morphometrics to test degree of plasticity in shape between marine and anadromous (i.e., ancestral) populations based upon salinity of the rearing environment. Our study indicated that the form of plastic responses differs between anadromous and marine G. aculeatus. Moreover, there was clear evidence that some of the shape variation between anadromous and marine fish is due to trait-based genetic differentiation. To the best of our knowledge, this is the first suggestion for any evolutionary system where two, differentially plastic, ancestral stems exist.
