Effects of isolation and environmental variables on fish community structure in the Brazilian Amazon Madeira-Purus interfluve

Abstract

Due to the existence of terrestrial barriers to freshwater fish dispersion, it is believed that its distribution is strongly associated with historical factors related to the formation of the habitats they occupy. By the other hand, some studies reveal the influence of abiotic conditions (such as size of water bodies, pH, conductivity) on the composition of fish fauna occurring in small streams. This study aimed to investigate whether drainage basins, because catchment boundaries are potential barriers to fish dispersion, or the physical structure and physico-chemical characteristics of water have a greater influence on fish community structure in small streams. We sampled 22 streams belonging to five drainage basins in the Madeira-Purus interfluve. Fish were caught with dip nets and a small trawl, and data were simultaneously obtained on structural characteristics of the streams and physico-chemical characteristics of the water. Community composition was analyzed using Non-Metric Multidimensional Scaling (NMDS), and variables related to structural and physico-chemical characteristics were summarized by Principal Component Analysis (PCA). Two explanatory models relating faunal composition to environmental factors were constructed: the first using only continuous variables and the second including the drainage basin as a categorical variable. The Akaike Information Criterion (AIC) and AIC weight were used to select the best model. Although structural and physico-chemical variables significantly contributed to explaining faunal composition, the model including the drainage basin was clearly the better of the two models (more than 90% support in the data). The importance of drainage basins in structuring fish communities in streams may have significant consequences for conservation planning in these environments.Keywords: Ichthyofauna, fish ecology, physical variables, chemical variables, western Amazon. Efeito do isolamento e das variáveis ambientais na estrutura de comunidades de peixes do interflúvio Madeira-Purus na Amazônia brasileira ResumoDevido à existência de barreiras terrestres à dispersão de peixes de água doce, acredita-se que sua distribuição é fortemente associada a fatores históricos relacionados à formação dos habitats que ocupam. Por outro lado, alguns estudos revelam a influência de condições abióticas (tais como o tamanho do corpo d'água, pH, condutividade) na composição da fauna ictiíca de rios de pequena ordem. Este trabalho teve como objetivo investigar se bacias hidrográficas, cujo divisor de águas representa uma potencial barreira para a dispersão dos peixes, ou a estrutura física e características físico-químicas da água têm maior efeito sobre a estrutura de comunidades de peixes de riachos de pequena ordem.

Effects of a small natural barrier on the spatial distribution of the fish assemblage in the Verde River, Upper Paraná River Basin,Brazil

“…Physical and chemical factors are pointed as important for determining the distribution and composition of fish assemblages (Matthews, 1998;Jackson et al, 2001;Oberdorff et al, 2001;Barros et al, 2013). However, in the present study we observed a weak correlation between selected environmental variables and geographical distance with the spatial structure of the ichthyofauna.…”

Stream ichthyofauna of the Tapajós National Forest, Pará, Brazil

“…The existence of dissimilarity in fish species composition of different, however geographically close, drainage systems within the Tapajos National Forest indicates that geographic isolation coupled with environmental characteristics is responsible for the structuring of fish communities, in accordance with observed by Schleuter et al (2012) in temperate regions and Barros et al 2013, in tropical streams. Furthermore the smaller drainage basins can significantly influence the stream fish assemblages composition (Mendonça et al 2005; Barros et al 2013) since headwaters streams often support exclusive species that do not occur in the river system, allowing constitute single assemblages that are fundamental to compose the regional fish diversity (Paller 1994; Meyer et al 2007) and must be priority included in units conservation planning for freshwater systems.…”

“…Furthermore the smaller drainage basins can significantly influence the stream fish assemblages composition (Mendonça et al 2005; Barros et al 2013) since headwaters streams often support exclusive species that do not occur in the river system, allowing constitute single assemblages that are fundamental to compose the regional fish diversity (Paller 1994; Meyer et al 2007) and must be priority included in units conservation planning for freshwater systems.…”

Influence of environmental variables on the relative abundance and habitat use of two sympatric notobranchiid fishes in a tropical stream

“…Different studies have investigated the relationships between biotic and abiotic factors, including geological factors, land cover and land use types, hydrological factors, stream habitat characteristics, stream order, and water quality on the biodiversity, individual species and even populations (Shahadat *Corresponding author. E-mail: badolax@yahoo.com Author(s) agree that this article remain permanently open access under the terms of the Creative Commons Attribution License 4.0 International License et al, 2012; Barros et al, 2013;Yong-Su Kwon et al, 2012;Humpl and Pivnicka, 2006;Kouamélan et al, 2003). According to Yong-Su Kwon et al (2012), these environmental factors are considered in a hierarchical structure ranging from large scale to small scale.…”

“…Studies on the influence of environmental variables on the existence and abundance of stream fishes has been done in the temperate regions but few has been conducted in the tropics especially Africa (Koel and Peterka, 2003;Toham and Teugels, 1997;Barros et al, 2013;Yong-Su Kwon et al, 2012;Humpl and Pivnicka, 2006;Kouamélan et al, 2003). Streams, swamps, small rivers and seasonal pools are generally extreme and highly variable even when not anthropogenically influenced (Ostrand and Wilde, 2002).…”