Abstract
Caves are excellent model systems to study the effects of abiotic factors on species distributions due to their selective conditions. Different ecological factors have been shown to affect species distribution depending on the scale of analysis, whether regional or local. The interplay between local and regional factors in explaining the spatial distribution of cave-dwelling organisms is poorly understood. Using the troglophilic subterranean spider Artema nephilit (Araneae: Pholcidae) as a model organism, we investigated whether similar environmental predictors drive the species distribution at these two spatial scales. At the local scale, we monitored the abundance of the spiders and measured relevant environmental features in 33 caves along the Jordan Rift Valley. We then extended the analysis to a regional scale, investigating the drivers of the distribution using species distribution models. We found that similar ecological factors determined the distribution at both local and regional scales for A. nephilit. At a local scale, the species was found to preferentially occupy the outermost, illuminated, and warmer sectors of caves. Similarly, mean annual temperature, annual temperature range, and solar radiation were the most important drivers of its regional distribution. By investigating these two spatial scales simultaneously, we showed that it was possible to achieve an in-depth understanding of the environmental conditions that governs subterranean species distribution.
Highlights
The distribution of a species depends on ecological and evolutionary processes occurring at both local and regional scales [1,2]
We extended the analysis to a regional scale to understand whether similar environmental predictors drive the species distribution at these two distinct spatial scales
In light of the initial data exploration, one outlier illuminance value was removed from the dataset and a log-transformation was applied to illuminance to homogenize its distribution
Summary
The distribution of a species depends on ecological and evolutionary processes occurring at both local and regional scales [1,2]. While regional scale processes can determine the species pool, the small-scale biotic processes and abiotic factors act as filters and determine which of these species becomes part of the community [4]. The scarcity of light, space, and nutrients in caves limits the number and abundance of resident species and selects for species adapted to a narrow ecological niche [5,6,7]. Due to these particular conditions, spatial patterns of subterranean organisms are usually very different from those observed in surface species [8,9]. Still little is known about global and regional macroecological patterns in subterranean biota [8,9,22]
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