Cave benthic invertebrates in south-eastern Brazil: are there 'key' factors structuring such communities?

Abstract

The aim of this study was to determine the effects of microhabitat traits related to water quality and physical features of stream channels (substrate, channel morphology and hydraulic characteristics) on the richness and structure of the aquatic insect assemblage in cave streams. Sampling was conducted in three subterranean streams in Brazil. Aquatic insect richness was significantly and positively related to water depth and the presence of shelters for invertebrates. These shelters are directly related to channel heterogeneity, a factor that determined the surface area of habitats suitable for colonisation, refuges and the amount and variety of nutrients in streams where resources are extremely limited. Furthermore, analyses of community composition revealed that aquatic insect assemblages in each cave were structured by distinct factors (including physicochemical characteristics of the water or hydraulic features of the channel). Together, these findings highlight that different factors are responsible for structuring the assemblages in each cave, which may reflect their local variability, and that silting of cave streams would likely have deleterious effects on aquatic insect communities through reductions in overall habitat heterogeneity.