Climate match fails to explain variation in establishment success of non-native freshwater fishes in a warm climate region

For non-native species, climate can act as a primary filter limiting establishment. Numerous studies examining climate similarity between native and introduced regions have been completed for temperate areas, however we know little about how well climate matching performs for warmer regions. For non-native freshwater fish introduced to warm regions, one potential problem with climate matching is that fish from both temperate and tropical source regions could establish. Our goal was to examine whether climate matching can predict the establishment of non-native freshwater fish for a warm climate region. We used CLIMATCH, a widely applied climate matching program, to analyze climate similarity between source and target regions for 37 successfully established species and 36 species that have failed to establish. CLIMATCH was calculated in two ways for successfully established species, with Florida records included (post hoc) and without Florida records (a priori). The mean post hoc score for successful species was higher than that of failed species; however, the mean a priori score for successful species did not significantly differ from failed species. On average, post hoc scores were inflated 1.5 times over a priori scores. The post hoc result is tautological-the scores are high because the species is successful, and the species is successful because the scores are high. These results highlight two issues for climate matching: (1) as commonly done post hoc, degree of climate match and predictive power may be overestimated and (2) a priori applications may lack predictive power. We recommend consideration of these issues in the use and interpretation of CLIMATCH for prediction. Additional research into regional importance of climate variables (temperature and precipitation) is warranted, especially in warm climate regions.