The environmental heterogeneity of sediment determines Chironomidae (Insecta: Diptera) distribution in lotic and lentic habitats in a tropical floodplain

1. Several limnological variables including sediments affect community structure in lotic and lentic environments. In general, Chironomidae larvae are dominant in macroinvertebrate communities both in abundance and in species richness in floodplains. Using granulometric texture as a surrogate for heterogeneity, we hypothesised that the diversity and distribution of Chironomidae larvae is higher in more heterogeneous environments. For this study, samples were collected quarterly from February to December 2008 at 12 stations in a tropical floodplain including both lotic and lentic stations in the Parana a River. 2. We recorded 66 morphospecies belonging to three subfamilies. Density, species richness and alpha diversity were greater in lotic versus lentic environments. Granulometric data were more diverse in lotic environments according to the Shannon-Wiener index. Different species dominated each environment, and these taxonomic differences were demonstrated by detrended correspondence analysis (DCA). The link between granulometric characteristics and chironomid assemblages were further established by a significant correlation between granulometric variables and one or both of the DCA axes. 3. Thus, the results support our hypothesis and suggest that the diversity and distribution pattern of Chironomidae larvae can be related to sediment heterogeneity due to the higher values of the assemblage attributes found in the lotic environments.