Tropical headwater streams and the role of non-native species on fish assemblage’s diversity

Santos, B.R.B. and Teresa, F.B. and Borges, P.P. and Casatti, L. and Tejerina-Garro, F.L. and Pompeu, P.S. and Benedito, E. and Carvalho, F.R. and Cetra, M. and Dias, M.S. and Súarez, Y.R. and Santos, T. and Brejão, G. and Carvalho, R.A. (2023) Tropical headwater streams and the role of non-native species on fish assemblage’s diversity. Biological Invasions, 25 (10). pp. 3103-3118. ISSN 1387-3547

Abstract

Non-native species cause several impacts on freshwater biodiversity, but studies focusing on the Neotropical stream’s biota are still incipient. We used a data set of 586 headwater stream’s fish assemblages from the Brazilian Upper Paraná ecoregion to test whether the presence/absence of non-native species affect: species richness (S), functional diversity (MPD) and taxonomic diversity (Δ+). We compared diversity patterns of fish assemblages formed only by native species against those of assemblages formed by native and non-native species (Scenario 1); then, we removed non-native species from their original assemblages and recalculated their diversity values to compare them with those of fish assemblages formed only by native species again (Scenario 2). We also investigated: (1) whether non-native’s fish assemblages are associated with land use, topographic and watercourse connectivity variables; (2) fish ecological traits-environment relationship. In Scenario 1, S was higher in assemblages with the presence of non-native species, while in Scenario 2, both S and MPD were higher in assemblages where non-native species were removed. Non-native species were not directly related to land use, topographic or connectivity variables and most of them had a similar response to the environment when compared with native species. Findings show that non-native fish species are related to high-rich assemblages in headwaters, and they increase species richness and the functional redundancy of assemblages, decreasing functional diversity. Moreover, in most cases, native and non-native species seem to respond similarly to the environmental influence on their occurrence.