Abstract
Being characterized by the absence of light and a reduced environmental cyclicity, the subterranean domain is generally regarded as temporally stable. Yet, in the proximity of cave entrances (twilight zones), patterns of sunlight and darkness can be detected within the 24-hour day–night cycle. In parallel, changes in the abiotic and biotic conditions are expected; however, these patterns have been rarely explored in animal communities dwelling in the twilight zone. We performed a biological investigation in a small abandoned mine in the Western Alps, monitoring it once per season, both during the day and at night. At each survey, we collected data on the spatial distribution of the resident species, their activity patterns, and the main microclimatic parameters. We observed significant daily variations in the environmental conditions during winter and spring, namely higher temperature, relative humidity and availability of trophic resources at night. In conjunction with these disparate nocturnal conditions, the abundance of troglophile species was also higher, as well as the activity patterns of one of the most frequent species inhabiting the entrance area – the orb-weaver spiderMetamenardi. We further documented temporal changes in the composition of the parietal community, due to species using the mine as a diurnal, nocturnal or overwintering shelter. Overall, our results suggest that the communities of the twilight zone are not temporally stable and we highlight the importance of taking into account not only their seasonal, but also their daily variations.
Highlights
Light availability plays a crucial ecological role for organisms on the earth surface (e.g., Panda et al 2002, Bradshaw and Holzapfel 2010, Gaston et al 2013, Tierney et al 2017)
The permanent darkness below the ground determines the absence of daily dark–light cycles and a reduced influence of the environmental cyclicity (Poulson and White 1969, Howarth 1980, 1983), two factors which seemingly triggered the reduction in the circadian components of activity of numerous cave-limited species over their evolutionary history (Trajano and Menna‐Barreto 1995, Hervant et al 2000, Trajano et al 2005, Moran et al 2014, Espinasa et al 2016)
Illuminance ranged from 900 lx in the vicinity of the entrance, to 0 lx at the end of the mineshaft
Summary
Light availability plays a crucial ecological role for organisms on the earth surface (e.g., Panda et al 2002, Bradshaw and Holzapfel 2010, Gaston et al 2013, Tierney et al 2017). The absence of light, at least from a biological point of view (see Badino 2000), represents the most crucial factor conditioning the ecology of subsurface habitats and the evolution of subterranean inhabitants (Pipan and Culver 2012, Battiston and Marzotto 2015, Culver and Pipan 2015, Konec et al 2015, Fišer et al 2016, Tierney et al 2017). There are seasonal turnovers in the species composition in a typical subterranean community
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
