We studied the ground‐dwelling spider assemblages along the receding Vedretta d’Amola debriscovered glacier foreland (central‐eastern Italian Alps). We addressed the hypothesis that species richness, abundance, and functional guilds of spiders are associated with age since deglaciation along the glacial foreland. We also hypothesized that species distribution on the glacier and along the foreland is related to specific environmental variables. We placed 25 pitfall traps along the glacier foreland and we sampled vegetation and soil. Sampling was performed during the period July‐September 2012‐2013. We collected 92 individuals belonging to 13 species. Results showed that both species richness and abundance of individuals increased along the glacial foreland, with the lowest values on the glacier and the highest on sites deglaciated for almost 150 years. Specifically, a strong stepwise‐increase in species richness and abundance appeared approximately 20 years after deglaciation. We observed that the number of functional guilds increased from early to late successional stage possibly in relation to higher habitat complexity and increased interspecific competition. Small spiders that spin small webs at ground level (Linyphiidae) dominate spider assemblages on the glacier. In the mid and late successional stages most of the spiders are funnel web spiders. Canonical correspondence analysis showed that the percentage of gravel and the vegetation cover are the main variables influencing the assemblages. Meioneta rurestris showed a higher preference for the sites on the glacier. On the other hand, Coelotes pickardi, Diplocephalus helleri, Mughiphantes handschini and Pardosa nigra were mostly related to the mid successional stages, while Drassodex heeri, Sitticus longipes and Arctosa alpigena to the late successional ones. According to the literature we confirmed that time since deglaciation influences spider species richness and assemblage composition; in addition the study of functional guilds offered a new opportunity to increase the ecological knowledge of the glacier foreland landform.
Distribution patterns in ground dwelling-spiders along a debris-covered glacier foreland
ISAIA, MARCO;
2014-01-01
Abstract
We studied the ground‐dwelling spider assemblages along the receding Vedretta d’Amola debriscovered glacier foreland (central‐eastern Italian Alps). We addressed the hypothesis that species richness, abundance, and functional guilds of spiders are associated with age since deglaciation along the glacial foreland. We also hypothesized that species distribution on the glacier and along the foreland is related to specific environmental variables. We placed 25 pitfall traps along the glacier foreland and we sampled vegetation and soil. Sampling was performed during the period July‐September 2012‐2013. We collected 92 individuals belonging to 13 species. Results showed that both species richness and abundance of individuals increased along the glacial foreland, with the lowest values on the glacier and the highest on sites deglaciated for almost 150 years. Specifically, a strong stepwise‐increase in species richness and abundance appeared approximately 20 years after deglaciation. We observed that the number of functional guilds increased from early to late successional stage possibly in relation to higher habitat complexity and increased interspecific competition. Small spiders that spin small webs at ground level (Linyphiidae) dominate spider assemblages on the glacier. In the mid and late successional stages most of the spiders are funnel web spiders. Canonical correspondence analysis showed that the percentage of gravel and the vegetation cover are the main variables influencing the assemblages. Meioneta rurestris showed a higher preference for the sites on the glacier. On the other hand, Coelotes pickardi, Diplocephalus helleri, Mughiphantes handschini and Pardosa nigra were mostly related to the mid successional stages, while Drassodex heeri, Sitticus longipes and Arctosa alpigena to the late successional ones. According to the literature we confirmed that time since deglaciation influences spider species richness and assemblage composition; in addition the study of functional guilds offered a new opportunity to increase the ecological knowledge of the glacier foreland landform.
I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
