Cave features, seasonality and subterranean distribution of non-obligate cave dwellers

Abstract

Seasonality impacts species distributions through changes of the environmental conditions that affect the presence of individuals at a given place. Although the dynamics of cave microclimates are well known, only a few studies have evaluated the effects of such dynamics on non-strictly cave species. Here we assessed if species exploiting subterranean environments show changes in habitat occupation related to seasonal variation of cave microclimates. We surveyed 16 caves in central Italy every month for one year. Caves were subdivided into longitudinal sectors of three meters. In each sector we measured cave morphology and microclimatic features, assessed the occurrence of eight non-troglobitic taxa (orthopterans, spiders, gastropods and amphibians), and related species distribution to environmental features and sampling periods. The occurrence of most species was related to both cave morphology and microclimatic features. The survey month was the major factor determining the presence of species in cave sectors, indicating that cave-dwelling taxa show strong seasonality in activity and distribution. For multiple species, we detected interactions between sampling period and microclimatic features, suggesting that species may associate with different microhabitats throughout the year. The richest communities were found in sites with specific microclimates (i.e., high humidity, warm temperature and low light) but seasonality for species richness was strong as well, stressing the complexity of interactions between outdoor and subterranean environments.

An ecological survey of the invertebrate community at the epigean/hypogean interface

“…According to the results of the GAMM, the prevalence of external elements dropped significantly during winter. Seasonal dynamics in faunal assemblages were observed by previous authors focusing on MSS (e.g., Crouau-Roy et al 1992, Nitzu et al 2011, Rendoš et al 2012, 2016a) and on caves (e.g., Tobin et al 2013, Ferreira et al 2015, Mammola et al 2015, Bento et al 2016, Lunghi et al 2017. It is possible to argue that, over the year, at the blurry epigean/hypogean interface, there are complex exchanges involving fauna with different levels of subterranean adaptation (Prous et al 2004, Moseley 2009, Novak et al 2012, which introduce fundamental trophic resources in the subterranean habitat (Novak et al 2013) but also cause greater fluctuations in species composition over the year.…”

Finding answers in the dark: caves as models in ecology fifty years after Poulson and White

“…It is well understood that most subterranean habitats are characterized by a constant flux of invaders and migrants, i.e. For instance, different arthropods may actively move from larger cave chambers to the stable network of fissures and vice versa (Chapman 1985), or rearrange their spatial distribution along the cave length in different seasons (Crouau-Roy et al 1992, Mammola et al 2015a, 2017a, Lunghi et al 2017. Moreover, there can be a temporal variability in the distribution of troglobionts inhabiting subterranean habitats.…”

“…He argued that, ecologically, caves can be seen as ecotones between the surface communities and the deep and more climatically-stable network of fissures -by many authors considered to be the 'true' subterranean habitat (Howarth 1983, Howarth and Stone 1990, Giachino and Vailati 2010. Suspending judgment on this debate, it is worth pointing out that the recent recognition of these surface-subterranean thresholds is fostering their increased utilisation as model systems in subterranean biology, especially for studying species-environment relationships (Lunghi et al 2017), interspecific interactions (Novak et al 2010b, Luštrik et al 2011, Mammola et al 2016b and adaptive radiations (Yao et al 2016). …”

Cave exploitation by an usual epigean species: a review on the current knowledge on fire salamander breeding in cave

“…When analysing cave biota, it is important to recognize that underground habitats are not a closed system (Romero 2009): besides the exchange of abiotic components (e.g. chemicals, air and water) with outdoor environments, many organisms (more or less occasionally) move in and out caves, being entirely or for a part of their life cycles linked to underground environments (Lunghi et al 2017).…”

“…However, most of studies on underground animals focus on obligate cave dwellers, while only few consider underground populations of usually epigeous species (Lunghi et al 2015;Lunghi et al 2017).…”