Hypolithic refuges: Influence of habitat availability, microclimate, and predation on hypolithic invertebrates in the eastern karoo, South Africa

Abstract

Abstract Invertebrate communities occupying hypolithic habitats at the rock-soil interface are diverse and can contribute significantly to ecosystem functioning, especially in arid environments. However, these communities are poorly understood. We tested three hypotheses of processes that may structure these communities, these reflecting species-area relationships, microclimate refuges and the effects of predation. We quantified the communities and the microclimate occurring beneath rocks of varying sizes and the response of the communities to the presence of a rock turning predator (chacma baboon Papio ursinus) in the eastern Karoo, South Africa. The observed community comprised 44 morphospecies, representing 15 Orders, and the microclimate under the rocks was significantly ameliorated from the upper and lower extremes of temperature and consistently moister than the surrounding habitat. However, the species-area relationship, role of microclimate and the presence of baboons are weak predictors of this community structure. This may be due to these processes interacting in complex ways, and these hypolithic patches functioning as habitat refugia rather than as discrete islands. We argue that understanding the role of hypolithic patches as refugia is important, given that such refugia may provide for community stability in the face of climate change, which would be particularly important in harsh arid landscapes.