Meeting Abstract
Environmental heterogeneity can result in phenotypic divergence in behaviour, physiology, and life-history strategies. We investigated the consequences of habitat variation on the athletic performance and reproductive investment of the amphibious fish Kryptolebias marmoratus. We hypothesized that life-history trade-offs are mediated by environmental quality, such that fish in a relatively well oxygenated freshwater pond would preferentially invest energy in reproduction while those from hypoxic crab burrows would have higher athletic capacity to improve competitive ability. To test these hypotheses we collected wild fish from a freshwater population and a salt water population on Long Caye, Belize. We measured body condition and tested biomechanical performance in water (predator escape response), leaving water (hypercapnia emersion response), and on land (tail-flip jumping). Contrary to our predictions, freshwater fish were both in better condition and showed better endurance compared to their salt water counterparts. Across habitat types our findings suggest that there is no obvious trade-off between athletic performance and reproductive investment in wild mangrove rivulus. Within habitat however, environmental quality matters. Poor quality habitats show no trade-off; fish with high gonadosomatic index are superior athletes. High quality habitats show a clear trade-off where high GSI appears to be correlated with a lower athletic performance. This data suggests that when resources are limited individuals balance their energy allocations while an abundance of resources leads to a greater investment in reproduction.
