The role of microhabitats in structuring cave invertebrate communities in Guatemala

Abstract

Several studies have tried to elucidate the main environmental features driving invertebrate community structure in cave environments. They found that many factors influence the community structure, but rarely focused on how substrate types and heterogeneity might shape these communities. Therefore, the objective of this study was to assess which substrate features and whether or not substrate heterogeneity determines the invertebrate community structure (species richness and composition) in a set of limestone caves in Guatemala. We hypothesized that the troglobitic fauna responds differently to habitat structure regarding species richness and composition than non-troglobitic fauna because they are more specialized to live in subterranean habitats. Using 30 m2 transects, the invertebrate fauna was collected and the substrate features were measured. The results showed that community responded to the presence of guano, cobbles, boulders, and substrate heterogeneity. The positive relationship between non-troglobitic species composition with the presence of guano reinforces the importance of food resources for structuring invertebrate cave communities in Guatemalan caves. Furthermore, the troglobitic species responded to different substrate features when compared to non-troglobitic species. For them, instead of the presence of organic matter, a higher variety of abiotic microhabitats seem to be the main driver for species diversity within a cave. The high specialization level of troglobitic organisms might be the reason why they respond differently to environmental conditions. The findings of this study highlight the importance of biological surveys for understanding cave biodiversity and give insights on how this biodiversity might be distributed within a cave. Conservation measures should keep in mind the target organisms and if such measures aim to protect a broad variety of organisms, then one should aim to preserve as many microhabitats and trophic resources as possible.