Spatio-temporal patterns of terrestrial macroinvertebrate assemblages at Gcwihaba Cave, Botswana

Abstract

Cave ecosystems harbour diverse and specialized macroinvertebrate communities that provide vital ecosystem services. This study investigated the within cave and seasonal patterns of terrestrial macroinvertebrate assemblages in Gcwihaba cave, Botswana. Prior to this study, the macroinvertebrate assemblages of Gcwihaba cave were only superficially surveyed and the temporal patterns of the invertebrate communities were unknown. This study therefore aimed to improve knowledge on the macroinvertebrate taxa that occur in the cave, their distribution across the cave sectors and the influence of climatic seasons on the distribution patterns of the invertebrates. To examine the community patterns, terrestrial macroinvertebrates were collected within three cave zones; the light sector, the transition sector, and dark sector. These collections were undertaken during the rainy season (hot-wet) and the winter season (cold-dry) using pitfall traps and visual surveys. A total of 31 macroinvertebrate taxa were collected, including 18 new families. Cave cockroaches (Blaberidae) were the most abundant, followed by cave crickets (Rhaphidophoridae) and violin spiders (Sicarridae). Species richness was similar across zones, but diversity (Shannon and Simpson indices) decreased from the light zone to the dark zone, indicating a shift from a balanced community to one dominated by specialized taxa. The abundance of macroinvertebrates was significantly higher in the dark zone and during the hot-wet season, likely due to increased resource availability and favourable microclimates. Seasonal variations influenced community composition, with some taxa exhibiting distinct seasonal preferences. In terms of the spatial distribution of macroinvertebrate groups within the cave, the patterns are similar to those reported by previous research, the main contribution of this research is the recording of 16 additional macroinvertebrate taxa in the cave and a demonstration that there is high macroinvertebrate activity during the rainy season; which may benefit approaches to the cave management.