Distributional dynamics of a specialized subterranean community oppose the classical understanding of the preferred subterranean habitats

Abstract

Troglobionts are organisms that are specialized for living in a subterranean environment. These organisms reside prevalently in the deepest zones of caves and in shallow subterranean habitats, and complete their entire life cycles therein. Because troglobionts in most caves depend on organic matter resources from the surface, we hypothesized that they would also select the sections of caves nearest the surface, as long as environmental conditions were favorable. Over 1 year, we analyzed, in monthly intervals, the annual distributional dynamics of a subterranean community consisting of 17 troglobiont species, in relation to multiple environmental factors. Cumulative standardized annual species richness and diversity clearly indicated the existence of two ecotones within the cave: between soil and shallow subterranean habitats, inhabited by soil and shallow troglobionts; and between the transition and inner cave zones, where the spatial niches of shallow and deep troglobionts overlap. The mean standardized annual species richness and diversity showed inverse relationships, but both contributed to a better insight into the dynamics of subterranean fauna. Regression analyses revealed that temperatures in the range 7–10°C, high moisture content of substrate, large cross section of the cave, and high pH of substrate were the most important ecological drivers governing the spatiotemporal dynamics of troglobionts. Overall, this study shows general trends in the annual distributional dynamics of troglobionts in shallow caves and reveals that the distribution patterns of troglobionts within subterranean habitats may be more complex than commonly assumed.

Microclimate and habitat heterogeneity as important drivers of soil Collembola in a karst collapse doline in the temperate zone

“…A three‐year study revealed an exceptionally high species richness of soil Collembola in Silická ľadnica Ice Cave, specifically 129 species within a very small area of 351 m 2 , and the presence of diverse microrefugia for many endemic and climatic relict taxa, such as cold‐adapted (psychrophilic) species with montane, disjunctive boreo‐montane and arctic–alpine distribution ranges (Raschmanová, Miklisová, et al, 2018). Generally, cave entrances represent dynamic environments with characteristic microclimate fluctuations (e.g., Mammola et al, 2017; Moldovan et al, 2018; Raschmanová, Šustr, et al, 2018) and are also considered to be functional ecotones for epigean (surface) and subterranean systems, revealing high local diversity and endemism of arthropods (Culver, 2005; Culver & Poulson, 1970; Kozel et al, 2019; Mammola et al, 2017; Papáč et al, 2019; Prous et al, 2004, 2015; Raschmanová, Miklisová, et al, 2018; Yao et al, 2016). Furthermore, the specific conditions of permanently cold habitats (near the floor ice) at the cave entrance may enhance speciation and diversity of arthropod communities, including cryptic taxa (Raschmanová et al, 2017).…”

Exploring the homogeneity of terrestrial subterranean communities at a local spatial scale

“…In a few cases, troglobionts also occurred in close proximity to the surface, although in low numbers. This was not an unexpected pattern as it has been shown that obligate subterranean species within different cave systems may present a bimodal distribution, with peaks in richness and abundance in close proximity to the surface and deeper inside caves (Novak et al, 2012;Kozel et al, 2019). Yet, in the cave system of Comba dell'Infernotto, the predicted and observed abundance in the vicinity of the surface was close to zero (Fig.…”

The role of microhabitats in structuring cave invertebrate communities in Guatemala

“…Troglobitic organisms might have suffered different ecological pressures over time when compared to troglophiles and trogloxenes, hence occupying an entirely different niche. Being adapted to the dark and oligotrophic cave environment, they can inhabit places that are not tolerable for most cave dwellers (Kozel et al, 2019).…”

“…Several studies have tried to elucidate the main environmental factors driving the invertebrate community structure (species richness and composition) in cave environments. The main factors highlighted as important are seasonality (Tobin et al, 2013;Mammola et al, 2015;Bento et al, 2016;Lunghi et al, 2017;Kozel et al, 2019), lithology (Souza-Silva et al, 2011b), landscape structure (Christman et al, 2016;Mammola & Leroy, 2017), distance from cave entrance (Ferreira & Martins, 1998;Prous et al, 2004;Tobin et al, 2013;Kozel et al, 2019), linear development of the cave (Simões et al, 2015;, presence…”