Increasing Functional or Phylogenetic Distance From Native Fish Communities Promotes Non-Native Fish Invasions in...

Biological invasions severely threaten ecosystems and their underlying drivers remain a subject of ongoing inquiry in ecology. Four mutually exclusive invasion hypotheses, biotic acceptance and resistance hypotheses and Darwin's preadaptation and naturalization hypotheses, have long drawn extensive attention. Furthermore, human activities and environmental factors are also widely recognized as key drivers of biological invasions. While integrative analyses of the aforementioned biotic and abiotic factors influencing biological invasions have been conducted previously, systematic global-scale analyses for freshwater fishes remain limited, constraining our understanding of large-scale invasion patterns in this taxon. Here, we leveraged a comprehensive database with taxonomic, functional, and phylogenetic data for 5245 freshwater fish species across 1411 global river basins to explore ecological correlates of non-native fish establishment. Specifically, we used taxonomic, functional, and phylogenetic facets of biodiversity to comprehensively quantify native communities (testing biotic acceptance and resistance hypotheses) and relatedness between native and non-native communities (testing Darwin's preadaptation and naturalization hypotheses). We further extracted environmental and anthropogenic variables across global rivers to assess external predictors of non-native fish establishment. Our results primarily supported Darwin's naturalization hypothesis: at the global level, native fish community invasibility peaked when non-native species exhibited great functional or phylogenetic distance from native communities, suggesting distantly related non-natives likely had unique traits or strategies to exploit vacant niches. Meanwhile, climatic factors also emerged as key drivers of global fish invasion patterns. At the biogeographic realm level, the determinants of fish invasions varied among the six realms, highlighting the complexity and regional specificity of biological invasions. However, our findings were based on correlational patterns of established non-native species at the basin scale and thus cannot establish definitive causal relationships between the identified drivers and establishment success. Future experimental manipulations at finer spatial and temporal scales are therefore required to validate the correlations observed in this study.