Influence of forest cover and mesohabitat types on functional and taxonomic diversity of fish communities in Neotropical lowland streams

Abstract

– In this study, we investigated how taxonomic and functional diversity of fish communities is influenced by forest cover and mesohabitat types in Neotropical lowland streams. We sampled fish fauna of 126 five‐metre‐long mesohabitats using an electrofishing unit in forested (n = 3) and deforested (n = 3) streams in the upper Paraná River basin, south‐eastern Brazil. According to velocity and depth, three mesohabitat types have been considered: riffles (shallow and fast‐flowing habitat), pools (deep and slow‐flowing habitat) and runs (intermediate depth and velocity). Seven functional traits and 27 trait categories related to ecological, behavioural and life‐history aspects of fish were considered. Our results indicate that forest cover and mesohabitat type influence fish communities in different ways. Whereas deforestation affects communities primarily through changes in diversity (functional and taxonomic), mesohabitat types determine changes in the functional composition. The increased diversity in deforested mesohabitats is driven by a decrease in species turnover among habitat patches within streams. This can be attributed to new feeding opportunities and microhabitat availabilities in deforested streams so favours the occurrence of species having a particular set of traits, indicating a strong habitat–trait relationship.

Ecomorphology and diet reflect the spatial segregation between two Siluriformes species inhabiting a stream of the Bodoquena Plateau, in Central Brazil

“…However, other studies focusing on other species of Imparfi nis, as well as I. schubarti, have confi rmed the results reported here (Ferreira & CasaTTi, 2006;silva et al, 2012). In contrast to the patterns observed for P. taenioptera, the less variable and strictly insectivorous diet exhibited by the studied riffle-dwelling species corroborates previous findings that have highlighted the dominance of insectivorous species with more specialized habitats in riffles (CasaTTi & CasTro, 1998;Teresa & CasaTTi, 2012). The fast water velocity and the limited availability of food items present in riffles (anGermeier & sChlosser, 1989) are restrictive conditions which, according to Teresa & CasaTTi (2012), are successfully explored by two dominant functional groups: benthicgrazers-periphytivorous species, as represented mainly by loricariid species, and benthic-speculators-insectivorous fish, as represented by heptapterid species.…”

“…These results are congruent with the temporally variable resources availability reported for pools (anGermeier & Karr, 1983). The opposite patterns have been suggested for riffl es, whose environmental conditions and resource availability would be less variable than found in pools (Teresa & CasaTTi, 2012).…”

“…Besides the predictive value of feeding habits on habitat use at microhabitat scale, some patterns may also be identified across broader scales. For example, some studies have suggested that riffles are usually associated with low spatial and temporal variability in food availability (anGermeier & sChlosser, 1989;Teresa & CasaTTi, 2012), while pools have more variable alimentary items available (anGermeier & Karr, 1984;BerKman & raBeni, 1987). These aspects could be reflected in the trophic structure of the assemblages, as we could expect that pool-dwelling fish species would have a higher spatial and temporal variation in the diet than riffle-dwelling species.…”

“…Geomorphological and hydrological characteristics of streams are important to determine environmental heterogeneity and habitat availability for aquatic biota (Gorman & Karr, 1978). Accumulated evidence indicates that fish distribution across habitats is not random; instead, the fish-habitat relationship is mediated by functional traits (PoFF, 1997;Teresa & CasaTTi, 2012;Pease et al, 2012). This biological determinism takes its roots in evidence of ecological and evolutionary processes that explain contemporary patterns of species distribution.…”

Effect of the riparian vegetation removal on the trophic network of Neotropical stream fish assemblage

“…Many studies (Bojsen and Barriga, 2002;Casatti, et al, 2012;Teresa and Casatti, 2012) have also showed the effects of riparian vegetation suppression on fish assemblage; i.e., it leads to their simplification, with a high dominance of tolerant species and loss of ecosystem services. Moreover, Casatti et al (2015) have found that although environments without riparian vegetation may have higher richness and diversity of fish, they also have a high functional redundancy, mostly related to feeding.…”