Meeting Abstract
Understanding the evolutionary trade-offs is important in predicting how species will respond to changing habitat conditions. The gulf killifish (Fundulus grandis) is native to the Gulf of Mexico but has been introduced in several rivers across North Texas. We evaluated patterns of selection on whole organism morphology in current and historical populations of Fundulus across its native range as well as introduced populations in inland freshwater rivers. Using landmark morphometrics, we found body shape differences between rivers and coastal sites, with river populations exhibiting body shape associated with unsteady swimming performance. We also found differences across time, where the earliest specimens from introduced sites more closely resembled coastal sites, showing that body shape in the current populations has diverged from the coastal ancestor. To understand what affect this had on performance, we also performed swimming performance assay to determine how body shape affected swimming ability. We found, consistent with our predictions, that fish from habitats with flowing conditions had more streamlined (unsteady) morphologies, and better swimming performance, than fish from populations with little/no flow. Ultimately, our results show how gross morphology is shaped over time in response to shifts in flow regimes.
