Increased population density depresses activity but does not influence emigration in the snail Pomatias elegans. (7th November 2020)

• Record Type: Journal Article
• Authors: Dahirel, M.; Menut, L.; Ansart, A.
• Is Part Of: Journal of zoology. Volume 313:Number 3(2021)
• Page Start: 172
• Page End: 181
• Publication Date: 2020-11-07
• Subjects: defence -- dispersal syndromes -- ecosystem functioning -- gastropod -- sex‐biased dispersal; Zoology -- Periodicals; Zoologie -- Périodiques; 590.5
• DOI: 10.1111/jzo.12846
• Languages: English
• ISSNs: 0952-8369

Abstract

Abstract: Dispersal is a key trait linking ecological and evolutionary dynamics, allowing organisms to optimize fitness expectations in spatially and temporally heterogeneous environments. Some organisms can either actively disperse or reduce activity in response to challenging conditions, and both responses may be under a trade‐off. To understand how such organisms respond to changes in environmental conditions, we studied emigration (the first step of dispersal) and activity behaviour in the gonochoric land snail Pomatias elegans, a litter decomposer that can reach very high local densities, over most of the range of ecologically relevant densities. We found that crowding had no detectable effect on emigration tendency in this species, contrary to previous results in many hermaphroditic snails. Pomatias elegans is nonetheless able to detect population density; we show they reduce activity rather than increase dispersal in response to crowding. We propose that limiting activity may be more advantageous than moving away in species with especially poor movement abilities, even by land mollusc standards, such as P. elegans . Interestingly, emigration and activity were positively correlated independently of density; this dispersal syndrome may reflect an underlying pace‐of‐life syndrome and is compatible with a dispersal‐dormancy trade‐off, which would require further investigation. Additionally, we found snails with heavier shells relative to their size tended to be less mobile, which may reflect physical and metabolic constraints on movement and/or survival during inactivity. We finally discuss how the absence of density‐dependent dispersal may explain why P. elegans is often found at very high local densities, and the possible consequences of this behaviour for ecosystem functioning and litter decomposition. Abstract : Dispersal is a key trait of organisms, which may in some cases help individuals escape stress such as crowding. In a small land snail, we found that high densities surprisingly had no effect on dispersal tendency. Instead, snails reduced activity at high densities. We discuss the consequences of dispersal and activity responses for ecosystem functioning in this litter decomposer.