The functional traits of host fish can act as good predictors for parasite composition in a Neotropical floodplain.

Parasite diversity can be influenced by the interaction of environmental factors and host traits, however, understanding which traits can be decisive for the establishment of the parasite can provide subsidies for a better understanding of the parasite-host relationship. In this study, we investigated whether functional traits, diet, and host phylogeny can predict the similarity of endoparasite composition of a fish assemblage in a Brazilian floodplain. Of the three evaluated components, the host's diet was the factor that presented the greatest influence on the composition and similarity of endoparasites, demonstrating the highest percentage of explanation. The functional traits and phylogeny, despite presenting significant values (unique effect and global effect), demonstrated low explainability in the composition of endoparasites. When analyzing the joint effects, all components showed significant influences. Hosts that live in the same environment that are phylogenetically related and that have a similar ecology, have a certain degree of homogeneity in their parasite assemblages and, because they are endoparasites (which are acquired trophically along the chain), diet is the main driver of parasite richness and similarity. Overall, host traits can be one of the main determinants of parasite composition, so studies that address the functional traits of the host provide a representation of local diversity and define the possible patterns of these parasite communities. This article is protected by copyright. All rights reserved.