Host diversity, phylogenetic relationships and local environmental factors drive infection patterns of a non-native parasite in tropical floodplain fish assemblages

Biodiversity, biological traits of potential host species, and environmental conditions may mediate the emergence of new diseases. We assessed the relative influence of such factors on patterns of infection by Austrodiplostomum compactum (Digenea, Diplostomidae) in fish assemblages of the Upper Parana River floodplain, Brazil. Multiple infection parameters were modeled at the community and species levels using phylogenetic diversity (PD), abundance (total and for a main reservoir species Plagioscion squamosissimus), local environmental conditions and phylogenetic distance from P. squamosissimus (Dis_Plag). In total, 108 fish species were collected and 28 were infected. At the community level, mean parasite abundance and mean infection intensity were positively associated with PD and the interaction between PD and environmental conditions, whereas host richness was negatively associated with PD. The complementary results indicate a biodiversity sampling effect rather than dilution effect. Environmental conditions often had the strongest coefficients in community-level models and mediated associations between infection parameters and other factors. At the species level, consistent negative associations between infection parameters and Dis_Plag indicate phylogenetic niche conservatism of parasites. Integration of community and species-level analyses demonstrates that phylogenetic diversity can affect host-parasite interactions in multiple ways, but that the associations depend on phylogenetic relationships and environmental conditions.