The ecological niche of a specialized subterranean spider

Abstract

Hypogean habitats offer unique opportunities for ecological studies because they are characterized by low abundance and diversity of organisms, they receive low energy inputs, they are relatively stable from a climatic point of view, and they are quite easily modeled. However, given the harsh conditions of the working environment and difficulty of access, very few studies have investigated in detail the ecology of subterranean species directly in the field. In this study, we describe the ecological niche of the subterranean spider Troglohyphantes vignai (Araneae, Linyphiidae). We monitored the population of T. vignai in a disused graphite mine in the Western Italian Alps over 1 year, and recorded the main biotic and abiotic parameters characterizing each sampling plot (i.e., temperature, humidity, prey availability, illuminance, and structural complexity). The ecological niche of T. vignai was modeled through polynomial generalized linear mixed models (GLMM) and illustrated graphically by means of three‐dimensional plots and GIS techniques. The environmental range in which the probability of presence of T. vignai was higher was consistent with a trade‐off between climatic stability and food availability. Neither temporal nor spatial variation of the niche of T. vignai was detected through the year. The methodology used here may be easily adapted to other hypogean sites, paving the way to a novel understanding of niche partitioning in subterranean ecosystems.

Climate change may drive cave spiders to extinction

“…In turn, this latter factor significantly increases the threat of global extinction because the rate of recolonisation is low (Cardoso et al 2011a, b). This is particularly evident for Troglohyphantes spiders, for which we previously demonstrated a very low dispersal ability within caves (Mammola and Isaia 2016) and extreme levels of population differentiation (Mammola et al 2015a).…”

“…Among the range of subterranean taxa occurring in the western Alps, we chose the cave-dwelling spiders Troglohyphantes (Araneae, Linyphiidae) as model organisms. The reliability of this model comes from empirical observations pointing out their preference for narrow, stable and cool microclimatic conditions (Deeleman-Reinhold 1978, Isaia and Pantini 2010, Isaia et al 2011, Mammola and Isaia 2016. Accordingly, Troglohyphantes spiders are characterized by moderate to high levels of troglobiomorphy (sensu Juberthie and Decu 1994) and show restricted or point-like ranges of distribution (Brignoli 1971, Deeleman-Reinhold 1978, Isaia and Pantini 2010, Isaia et al 2011).…”

Spiders in caves

“…Being top predators, spiders are preferentially found in preyrich areas, where they maximize food intake [5,11,12,98]. Many subterranean spiders also evolved unusual foraging behaviours and feeding habits, in order to comply with the general low prey availability.…”

“…Among other subterranean taxa, spiders are distinctive for their ecological role of top predators [3][4][5], and for the variety of functional adaptations [6], therefore representing undervalued models for the understanding the evolution of life in extreme habitats. Accordingly, subterranean spiders have served as models for physiological [7][8][9], ecological [4,5,[10][11][12], ethological [13,14] and biogeographic studies [15][16][17], among others.However, compared with other animal groups, the potential of spiders as model organisms is still under-expressed. It is possible that the paucity of studies is related to the difficulty of working in subterranean habitats and to the rarity of most subterranean species, which pose major impediments to data collection and analysis.…”

The deep subterranean environment as a potential model system in ecological, biogeographical and evolutionary research

“…Mammola and Isaia (2016) studied the environmental niche of a subterranean spider (Troglohyphantes vignai Brignoli, 1971) during a year, concluding that although some minimal spatial climatic variation was detected, neither temporal nor spatial variation of the niche of this species was found through the year. Finally, caves harbour comparatively simple biological communities (Racovitza 1907, Culver and Pipan 2009, Cardoso 2012, which minimizes the additional complexity of biological interactions.…”