107.4 Sunday, Jan. 6 Piscivorous fish in a fishless environment: dietary and phenotypic differentiation of bigmouth sleepers in Bahamas blue holes MARTIN, RA*; LANGERHANS, RB; NIMBioS; North Carolina State Univ. email@example.com
Ecology’s role in driving predictable differentiation between populations is a central topic in evolutionary ecology. Based on a priori knowledge of theory and natural history, just how predictable are organism’s responses during times of ecological change? Here, we use the model system of inland blue holes in the Bahamas to test the predictability of dietary, demographic, and phenotypic differentiation following the invasion of an otherwise fishless environment by a piscivorous fish, the bigmouth sleeper (Gobiomorus dormitor). In its ancestral environment of coastal streams and lakes, the bigmouth sleeper is a benthic, ambush predator, feeding primarily on fish and large invertebrates. On Andros Island, The Bahamas, bigmouth sleepers have colonized numerous land-locked blue holes. These isolated blue holes harbor depauperate fish communities, with bigmouth sleeper often co-occurring with only one other fish species, the small, livebearing Bahamas mosquitofish (Gambusia hubbsi). However, bigmouth sleepers inhabit two isolated blue holes in which no other fish species are present. Without any potential fish prey (other than cannibalism), how has their diet diverged? And has this shift in ecological environment driven changes in population and phenotypic characters, such as density, habitat use, size structure, sex ratio, feeding performance, and locomotor and trophic morphology? We first use existing ecological and biomechanical knowledge to build a set of predictions for ecological differentiation, and test them using comparative and experimental approaches. We find that bigmouth sleepers have diverged in many ways between populations with and without potential fish prey, mostly (but not always) in manners consistent with our predictions.