Abstract
Caves share unique conditions that have led to convergent adaptations of cave-dwelling animals. In addition, local factors act as filters on regional species-pools to shape the assemblage composition of local caves. Surveys of 35 Levantine caves, distributed along a climate gradient from the mesic in the north of Israel to hyper-arid areas in the south of Israel, were conducted to test the effect of cave characteristics, location, climate, bat presence, and guano level on the spider assemblage. We found 62 spider species and assigned four species as troglobites, 28 as troglophiles, and 30 as accidentals. Precipitation, elevation, latitude, minimum temperature, and guano levels significantly affected the composition of cave-dwelling spider assemblages. Caves situated in the Mediterranean region had higher species richness and abundance, as well as more troglobite and troglophile arachnids. These discoveries contribute to the knowledge of the local arachnofauna and are important for the conservation of cave ecosystems. By comparing spider assemblages of Levantine caves to European caves, we identified gaps in the taxonomic research, focusing our efforts on spider families that may have additional cryptic or yet to be described cave-dwelling spider species. Our faunistic surveys are crucial stages for understanding the evolutionary and ecological mechanisms of arachnid speciation in Levantine caves.
Highlights
IntroductionSubterranean habitats (caves and other hypogean habitats) around the world can be found in different climates, rock formations, and biogeographical regions
We showed that Levantine cave spider assemblages are diverse and are affected by the specific geographic location and its climatic characteristics, as well as by the presence of bats and guano level
In one analysis, we found a significant effect of the surrounding rock type on the spider assemblage, but most of our caves are located in carbonate rocks (27 of 35) and more samples from basaltic, chalk, marlstone, salt, and sandstone caves are needed in order to have a more balanced analysis
Summary
Subterranean habitats (caves and other hypogean habitats) around the world can be found in different climates, rock formations, and biogeographical regions. They can be formed by various means such as volcanic, glacial, mechanical, and erosion/solution processes. The majority of these subterranean habitats share unique abiotic conditions such as a limitation of light, stable and narrow range of temperature, and high relative humidity [1,2,3]. The peculiar abiotic conditions found in subterranean habitats, together with specific regional and local factors, determine species richness and assemblage composition of a particular cave. Processes at the regional scale include geological and climatic events together with historical biogeography, dispersal, extinction, and speciation, which shape the regional species pool [4,5,6]
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