Epigean and hypogean drivers of Neotropical subterranean communities

Abstract

Aim: In addition to cave size and other subterranean habitat characteristics, cave entrances are important structurers of neotropical cave communities. However, little is known about the epigean ecosystems factors that might dictate the influence of entrances and the relationship among surface and cave communities, as entrance regions are ecotonal zones between the epigean and hypogean ecosystems. We aimed to assess the influence of epigean and hypogean factors as potential drivers of invertebrate species richness in Neotropical caves as well as the influence of the regional pool of invertebrate diversity on cave invertebrate diversity. Location: Limestone caves in southeastern Brazil. Taxon: Invertebrates Methods: Data were collected in 48 caves within the Cerrado biome (Brazilian Savanna). The fauna sampling was performed by a direct intuitive search (DIS). Landscape characteristics and climatic parameters were accessed using geographic information systems. The characterization of the caves occurred during each sampling event. Regional diversity was based on the Taxonomic Catalog of Brazilian Fauna. To clarify the factors that significantly influence invertebrate species richness of the caves, we used generalized linear models (GLM). The relationship between regional diversity and cave diversity was evaluated based on linear models (LM). Results: Overall, 1,173 species were found, of which 72 were obligate subterranean dwellers. The cave total species richness was influenced by hypogean factors and epigean factors. The species richness of obligate cave dwellers was significantly explained only by cave size. The regional pool of invertebrate species influenced the levels of biodiversity in the studied caves. The taxa with troglobitic species tended to be more diverse in caves than expected. Main conclusions: In addition to the influences of intrinsic cave variables, we highlight the importance of epigean factors on subterranean diversity in the Neotropics. The study shows the significant influence of the regional species pool on cave faunal composition. These findings reinforce the importance of considering the surrounding areas in actions regarding cave biodiversity conservation.

Optimizing speleological monitoring efforts: insights from long-term data for tropical iron caves

“…For each data subset containing a given number of observations (surveys) we performed ten random samplings without replacement, to ensure the sampling of different sampling dates. Full-size  DOI: 10.7717/peerj.11271/fig- 3 Subterranean communities have been shown to be affected by seasonality, environmental conditions, cave characteristics, and the structure of surrounding landscapes (Simões, Souza-Silva & Ferreira, 2015;De Bento et al, 2016;Mammola & Isaia, 2018;Salvidio et al, 2019;Pellegrini, Faria & Ferreira, 2020;Rabelo, Souza-Silva & Ferreira, 2020). However, our results reveal that overall community composition was only weakly influenced by these factors, as our model explained merely 13% of total variation in community composition (Table 2).…”

The Água Clara Cave System in Northeastern Brazil: The Richest Hotspot of Subterranean Biodiversity in South America

“…However, in contrast to temperate regions, external primary productivity was not found to have a significant influence on the richness of troglobitic species in Brazil [70]. This is possibly due to the high productivity observed in tropical regions, where even areas with relatively low productivity can provide sufficient resources for cave-restricted species [70]. As a result, factors other than external productivity are likely to have shaped the ecology and evolution of these species in tropical regions.…”

“…In temperate regions, cave-restricted species are significantly influenced by epigean primary productivity since the amount of organic resources in surface environments potentially affects the availability of resources in subterranean ecosystems [1]. However, in contrast to temperate regions, external primary productivity was not found to have a significant influence on the richness of troglobitic species in Brazil [70]. This is possibly due to the high productivity observed in tropical regions, where even areas with relatively low productivity can provide sufficient resources for cave-restricted species [70].…”

From the front door to the basement: Invertebrate communities' structure as a proxy for determining cave zonation in Neotropics

“…Cave entrances serve as conduits for resource influx from the surface environment into the subterranean realm (Mammola, 2019;Mendes-Rabelo et al, 2021;Peck, 1976;Prous et al, 2004Prous et al, , 2015.…”

“…Additionally, harsh surface environmental conditions, exacerbated by rising deforestation rates (Cardoso et al, 2021(Cardoso et al, , 2022Souza-Silva et al, 2015), may prompt certain epigean species from the regional pool (Mendes-Rabelo et al, 2021) to migrate towards entrance regions, forming what's known as the para-epigean community (Prous et al, 2004), driven by resource availability and stable climatic conditions. This migration could potentially enhance local species richness (Mendes-Rabelo et al, 2021).…”