Meeting Abstract
Empirical studies of adaptation in nature reveal that trade-offs between competing functions are common. Such trade-offs are expected because whole organisms represent integrated systems, such that changes in any one trait will impact other traits. Bone and skeletal attributes represent a highly-integrated trait that influences a wide range of functions, including locomotion, protection, and mineral storage, but whether populations adapted to different environment exhibit different bone structure has gone largely unexplored. We compared the bone structure of field collected Trinidadian guppies adapted to lowland streams where predators are common, and headwater streams where predators are rare. We found significant and parallel differences in the exo- and endo-skeletons. Specifically, guppies from lowland streams had reduced bone density and mineralization of the exterior scales and endoskeleton, while their upstream counterparts had highly mineralized scales and skeletons. These differences appear to have a genetic basis, as the differences persisted after rearing guppies in the lab on the same diet. We discuss alternative hypotheses for why these differences might be adaptive, and the implications for how traits are integrated across these contrasting environments.
