Phenotypic and behavioral variation as a mechanism behind the invasive potential of a predatory neotropical fish

Modern biological invasions represent a major facet of the Anthropocene, yet the invasive potential of species remains poorly understood. In this context, this study compared ecological traits of native and non-native populations of Cichla kelberi, a powerful invader, to investigate the hypothesis that this fish exhibits phenotypic and behavioral variations, which may confer adaptability to different conditions. Data on population structure, trophic ecology, and reproduction were collected from populations in different Neotropical impoundments. We found differences in population structure, with larger mean sizes and a lower proportion of juveniles in the native population. All populations exhibited piscivore behavior, but a higher incidence of empty stomachs and a less diverse diet characterized some non-native populations, with the consumption of non-fish resources and cannibalism. Non-native populations also showed prolonged reproduction and early maturity. In general, differences were not restricted to the contrast native vs. non-native, as introduced populations showed considerable divergence among themselves. Results confirmed the existence of phenotypic and behavioral variation in C. kelberi, which must affect its invasive potential by conferring adaptability to novel conditions in specific localities and contexts. These aspects make C. kelberi an almost certain invader of artificial impoundments located in tropical ecosystems of the world.