Seasonal variations in cave invertebrate communities in the semiarid Caatinga, Brazil

Abstract

The Brazilian semiarid region has a clear distinction between the dry season, which can last up to nine months, and the rainy season. Caves are connected to different extents to surface ecosystems, although they are idealized as stable environments due to their isolation. Furthermore, little is known about the effects of wet and dry seasonal variations on underground biological assemblages. Invertebrate communities were analyzed during dry and rainy seasons in 24 caves in the semiarid region of northeastern Brazil. We also investigated whether the environmental stability of caves attenuates the effects of seasonality in this particular region. Morphospecies richness and abundance and the diversity indexes of caves were significantly higher during the rainy season. In addition, more stable caves showed less variation in the community composition between seasons. Our data point to a clear influence of the surface ecosystems on the caves in Caatinga. However, the intensity of this influence apparently depends on the environmental stability of the cave, and the most stable caves present smaller changes in the structure of their invertebrate communities during different seasons.