Habitat heterogeneity shapes cave invertebrate communities: insights from two caves at contrasting elevations

Abstract Understanding how subterranean communities are structured requires evaluating both local ecological processes within caves and the broader environmental context in which they occur. In this study, we examined patterns of species richness, composition, and beta diversity of terrestrial invertebrates in two large carbonate caves located at contrasting elevations: Umajalanta Cave in Bolivia (2850 m a.s.l.) and Morena Cave in Brazil (794 m a.s.l.). Despite their distinct altitudinal settings, both caves share broadly comparable structural features, including extensive passages, stream systems, and relatively complex internal topology. Environmental variables related to habitat heterogeneity, trophic resource availability, microclimatic conditions, and distance from the entrance were measured in 23 sectors (mesoscale, 3 × 10 m) and 69 quadrats (microscale, 1 × 1 m). Invertebrates were sampled through active visual searches. At the mesoscale, none of the environmental variables evaluated exhibited a significant relationship with species richness in Umajalanta Cave. In contrast, species richness in Morena Cave was positively associated with substrate diversity and trophic resource availability. At the microscale, species richness increased significantly with increasing distance from the cave entrance in both systems. However, positive relationships between richness and the availability of trophic resources and shelters were detected exclusively in Morena Cave. Beta diversity was high in both caves and across spatial scales, driven primarily by species turnover and indicating strong compositional heterogeneity at the mesoscale and microscale. Overall, our results indicate that cave invertebrate assemblages are primarily structured by local ecological processes operating within caves rather than by the altitudinal context in which they occur, although this inference should be interpreted cautiously given that only two caves were analyzed. Implications for insect conservation These findings underscore the importance of local environmental conditions and habitat heterogeneity in structuring subterranean communities, reinforcing the need to preserve both environmental integrity and habitat diversity within subterranean ecosystems.