Multiple studies have gathered evidence about the negative effects that the presence of non-native species may have on native populations. Within fragmented environments, such as urban ecosystems, native species might be more susceptible due to isolation, limited dispersal capabilities, or reduced availability of resources. We used an ecological reserve immersed within Mexico City as a model system to examine the potential negative effects of the presence of non-native species on native populations. We focused on distinct pairs of native/non-native species with ecological similarities that may have developed a competitive interaction. We used two-species occupancy models to estimate the probability that the presence of a given non-native species affects the presence of a native species. We predicted that competition could increase during the most limiting season of the annual cycle (dry season) followed by a weaker negative interaction during the season in which resources are more abundant (rainy season).
Our results indicate little evidence of spatial interactions between non-native and native species. Some of these interactions might reflect the co-occurrence of species due to the availability of resources that humans living in the surrounding urban areas constantly provide. Overall, the presence of typically invasive non-native taxa showed no negative effects on most of the native species that we studied. These results suggest that this urban reserve has the capacity to sustain populations of both native and non-native species. We also emphasize the need to maintain, preserve, and continue monitoring the local biota to enhance our understanding of the processes taking place in this ecological reserve immersed within a megacity.