Understanding the drivers of biological invasions is critical for preserving aquatic biodiversity. Stream fishes make excellent model taxa for examining mechanisms driving species introduction success because their distributions are naturally limited by catchment boundaries. In this study,we compared the relative importance of catchment-scale abiotic and biotic predictors of native and nonindigenous minnow (Cyprinidae) richness in 170 catchments throughout the eastern United States. We compared historic and contemporary cyprinid distributional data to determine catchment-wise native/nonindigenous status for 152 species. Catchment-scale model predictor variables described natural (elevation, precipitation, and flow accumulation) and anthropogenic (developed land cover,number of dams) abiotic features, as well as native congener richness. Native congener richness may represent either biotic resistance via interspecific competition, and trait preadaptation according to Darwin's naturalisation speculation. We used generalised linear mixed models to examine evidence supporting the relative roles of abiotic and biotic predictors of cyprinid introduction success. Native congener richness was positively correlated with nonindigenous cyprinid richness and was the most valuable variable predicting nonindigenous cyprinid richness. Mean elevation had a feeble positive effect,and effects of other abiotic factors were insignificant and less valuable. Our results suggest that at this spatial scale, trait preadaptation may be more valuable than intrageneric competition for determining richness of nonindigenous fishes.
Source: usgs.gov