Brito Oliveira, Marcos SidneySousa Valentim, David SalesFlores Gonzales, AnaiTavares Dias, Marcos2026-07-162026-07-162026-05-05Oliveira, M. S. B., Valentim, D. S. S., Gonzales, A. P. P. F., & Tavares-Dias, M. (2026). Are host phylogeny and ecology two major determinants in parasitic structuring in fish? Studies on Neotropical Fauna and Environment, 1–7. https://doi.org/10.1080/01650521.2025.2599341https://hdl.handle.net/20.500.12921/966The present study evaluates the metazoan parasite fauna of two fish species with similar feeding habits, but which are phylogenetically distant, to understand the degree of similarity in the parasites fauna between these host species. In all, 30 specimens of Chalceus epakros and 30 of Tetragonopterus chalceus were analyzed. A total of 1572 parasites were collected, 1414 in C. epakros and 158 in T. chalceus. The PERMANOVA showed that the ectoparasite community of C. epakros and T. chalceus has a high difference (R2 = 0.813; F = 235.41; p = 0.001); while for endoparasites, this difference reduced drastically (R2 = 0.156; F = 9.262, p = 0.001). When combining the two groups (ectoparasites + endoparasites), the difference between the groups increased again (R2 = 0.730; F = 146.49, p = 0.001). High differences observed between C. epakros and T. chalceus when considering only ectoparasites were due to the fact that both host species were not phylogenetically related; in this case, these differences were caused by Monopisthocotyla, parasites known for their host specificity. On the other hand, the high similarity in endoparasite composition occurred because these two host species occupy the same position in the food chain and consume the same food items.application/pdfeninfo:eu-repo/semantics/openAccesshttp://creativecommons.org/licenses/by/4.0/Amazonfreshwater fishJari Riverparasitic ecologytrophic webArticle