Abstract
ABSTRACT Changes in the landscape where watersheds are located may affect the stream biota in different ways. In order to explore this idea, we collected freshwater crabs of the genus Aegla Leach, 1820 in subtropical region of southern Brazil. We also measured a number of landscape features and physico-chemical variables in the collection streams and surroundings in order to ascertain which factors affect the occurrence of these crustaceans. A total of 167 individuals of Aegla were collected in 21 streams. The collection was comprised of three species: A. odebrechtii, A. platensis, and A. singularis. The occurrence of A. platensis was influenced by physico-chemical variables (total carbon and total organic carbon) and stream morphometry factors (level curves sum). The occurrence of A. singularis was influenced by land use (pasture and exposed soil and agriculture) and the stream morphometry (level curves sum). Only a small number of A. odebrechtii were collected and their occurrence was influenced by land use (pasture and exposed soil and agriculture). The topography of the area studied limits the types of land use and areas that are less favorable for agriculture (more hilly areas) are have more riparian vegetation (or less anthropic stress). As a result, these areas are less subject to changes in water quality, which is reflected in the distribution of Aegla species.
Highlights
Changes in the landscape where watersheds are located may affect the stream biota in different ways
The main question of this work was: does the landscape surrounding streams affect the occurrence of freshwater crabs? In addition, we evaluated the variation of limnological variables, stream morphometry characteristics, and land cover in drainage watersheds of streams and their effects on the occurrence of aeglids
The streams located in the northern region (29.5±1.0 %; average±SE) showed greater declivity that the streams in the south (16.3±3.1 %)
Summary
Changes in the landscape where watersheds are located may affect the stream biota in different ways. The occurrence of A. singularis was influenced by land use (pasture and exposed soil and agriculture) and the stream morphometry (level curves sum). The topography of the area studied limits the types of land use and areas that are less favorable for agriculture (more hilly areas) are have more riparian vegetation (or less anthropic stress) As a result, these areas are less subject to changes in water quality, which is reflected in the distribution of Aegla species. Factors can encourage human activities in the catchment area intensifying erosion and interfering with the dynamics of surface water resources (Oliveira et al, 2008; Santos & Sobreira, 2008) These morphometric characteristics may be associated with the occurrence and distribution of aquatic organisms (Ribeiro & Salomão, 2003)
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