Long-term impact of an invasive predator on the diversity of fish assemblages in a neotropical reservoir

The invasion of predators can result in taxonomic, functional and phylogenetic losses in the structure of fish fauna causing ecological damage in the invaded area. We tested the hypothesis that the invasion of the silver croaker (Plagioscion squamosissimus) altered the structure of fish assemblages in a Neotropical reservoir. Using data from long-term fisheries of the Jaguari Reservoir, Brazil, we calculated taxonomic (richness, evenness and beta diversity), functional (richness, evenness and beta diversity) and phylogenetic (richness, dispersion and beta diversity) metrics of diversity of fish assemblages per year and correlated them with the abundance of the invasive fish. We found that the invasion of P. squamosissimus affected all three facets of diversity. Alpha diversity decreased after the invasion, while beta diversity (both taxonomic and functional) and phylogenetic dispersion increased as P. squamosissimus abundance increased. Plagioscion squamosissimus was successful in the invasion process and became the most abundant predator in the reservoir few years after the first record. The generalist reproductive and feeding strategies of this predator, and the distant phylogenetic relationship with the local ichthyofauna may have facilitated its success. As a top predator in the food network, the invader likely interacted with the community mainly through predation and competition, thereby reshaping the fish community structure. We conclude that the P. squamosissimus invasion negatively affected the local biodiversity by detrimental changes to its taxonomic, functional and phylogenetic structure.