Isolation and lagoon morphometry define fish diversity and composition in nearshore areas of floodplain lagoons of the southern pantanal

Abstract

Floodplain lagoons support high fish diversity, but the role of local vs. regional factors in structuring assemblages is little studied in the Brazilian Pantanal. Aiming to understand the importance of limnological, biological, and regional characteristics shaping fish assemblages in the Pantanal floodplain, we sampled 26 lagoons in the Rio Negro floodplain from September 2005 through November 2006. Our results suggest that widely distributed species are also more abundant locally. Fish species richness is defined by a combination of isolation level, area and mean depth of lagoons, while evenness is determined mainly by macrophyte richness, lagoon area, water conductivity and distance to the river. Distribution of the most abundant fish species in sampled lagoons was explained by macrophyte biomass, lagoon area, shoreline development index and macrophyte richness. Overall, a general pattern of species diversity and distribution was primarily defined by a regional characteristic, namely, isolation, interacting with lagoon morphometry, and secondarily by biotic characteristics.