Factors Related to Non-Native Green Swordtail Local Persistence

Few small-bodied, tropical ornamental fish have successfully established in subtropical Florida, which may be due to multiple factors including biotic resistance and low habitat match. Yet, in some locations, the Green Swordtail Xiphophorus hellerii, a non-native poeciliid popular in the aquarium trade, exhibits persistent reproducing populations. Our primary question was what factors contribute to the apparent persistence of the Green Swordtail in Florida. We focused on thermal tolerance, propagule pressure, agonistic interactions with native Eastern Mosquitofish Gambusia holbrooki and facilitation by a novel non-native poeciliid predator, the Pike Killifish Belonesox belizanus. We used a combination of cold tolerance trials, field surveys, feeding trials and mesocosm experiments to address our question. Initial results indicate propagule pressure and sympatry with Pike Killifish promote and reduced habitat match due to thermal intolerance limits persistence of the Green Swordtail. Importantly, Pike Killifish removed Eastern Mosquitofish which typically reduce the recruitment of other poeciliids. These results suggest the distribution of Eastern Mosquitofish and its ability to limit reproduction of ornamental fish may vary over the landscape, dictated by landscape scale variation in temperature, propagule pressure and the presence of Pike Killifish.