Similarities in correlates of native and introduced fish species richness distribution in Brazilian reservoirs

We assessed the relationships among native and introduced fish species richness and a set of explanatory variables, including area, altitude, reservoir age, temperature, human influence index and fish abundance. We expected to find different relationships based on species origin (i.e., native or introduced). Based on compiled data from Brazilian reservoirs, we modeled the variation in the number of native and introduced fish species by generalized linear mixed models with different spatial autocorrelation structures. Reservoirs located in warmer regions and with higher fish abundance showed higher species richness of both native and introduced fish. Reservoir age tended to be negatively correlated with native species richness. Our results suggest that reservoir communities in warmer regions may be more resistant to local extinctions caused by impoundments, but they are more susceptible to species introductions. Our results also highlight that an extinction debt can be expected for native species because older reservoirs showed lower native species richness.