Abstracts (first author)
Allometric constraints on adaptive radiation in sticklebacks
The morphological differences between the marine ancestor and the descendant freshwater populations of threespine sticklebacks constitute a well-studied example of a phenotypic radiation. However the exact selective agents that drive these changes are not yet fully understood. We present a comparative study across 74 freshwater populations of threespine sticklebacks in Norway to test whether evolutionary changes in stickleback morphology can be explained as adaptations to lake characteristics thought to reflect different habitats and feeding niches. Only weak indications of adaptation were found, and the rates of adaptation varied from immediate to more constrained evolution among traits. Instead, populations have diversified in phenotypic directions predictable from allometric scaling relationships. This indicates that evolutionary constraints may have played a role in structuring phenotypic variation across freshwater populations of stickleback.