Macroecological assessment of invasive species impact on Japanese lake fish communities using eDNA metabarcoding.

Biological invasion has negative effects on ecological interaction such as competition and predation. The ecological impacts on native communities may also affect two processes that are important in determining community structures, namely, the environmental and spatial processes. Here, we used lake fish species compositions estimated using environmental DNA metabarcoding to investigate the effects of invasive species composition on the native community and on the processes that determine it. The results of PERMANOVA indicated that the native fish assemblage patterns significantly changed along invasive species compositions. Furthermore, it was observed that the diversity of invasive species acted as a potent ecological filter, driving native fish communities towards biological homogenisation. Distance-based Redundancy Analysis revealed that invasive species alter the relationship between ecological communities and their environment. The study suggests invasive species may obscure distinct environmental signals, potentially by having broader environmental tolerances than native species. A comparison of the relative importance of environmental factors and spatial structure in determining species composition between communities, fish species composition in lakes is more strongly influenced by environmental factors than spatial structure, although the predictive power of these factors varies with the presence of invasive species and is most evident in native-only communities. Our results suggest that the need to understand the impacts of invasive species on native species not only through direct effects, but also the complex effects involving the diversity level of invasive species.