Abstract
ABSTRACTBody size is one of the most important individual traits, determining various other life-history traits, including fitness. Both evolutionary and ecological factors shape the body size in arthropods, but the relative contribution of abiotic drivers acting at different spatial scales has been little investigated. We aimed to identify the importance of two broad-scale variables (study region and elevation) in shaping body size of the free-running and locally abundant wolf spider Pardosa palustris (Linnaeus 1758), in contrast to the fine-scaled variable topographic position. Therefore, we set up transects along environmental gradients in the arctic-alpine ecosystems of Norway, which we analyzed using a random forest approach to identify the relative importance of topographic position, elevation, and study region on body size of P. palustris. Our approach revealed that research region was the best explanatory variable, followed by elevation and topographic position. Differences in body size were most likely a consequence of the pronounced differences in season length and the ability of P. palustris to avoid local unfavorable environmental conditions due to its high mobility.
Highlights
The identification of spatial patterns in life-history traits, as well as the mechanisms that generate and maintain them, is mandatory in ecological field studies
163 adult female and 651 male specimens of P. palustris were sampled and measured during three trapping periods, corresponding to six weeks of sampling; juveniles were excluded in this study
Trying to disentangle the influence of fine- vs. broadscale ecological factors on body size of a highly mobile spider, we found that the effects of the broad-scale factors of study region and elevation were both more important than the fine-scaled factor of topographic position
Summary
The identification of spatial patterns in life-history traits, as well as the mechanisms that generate and maintain them, is mandatory in ecological field studies. This will, result in a better understanding of spatio-temporal patterns of species distribution and adaptations in response to changing environments. Knowledge about specific spatial and temporal variations of life history traits remains scarce in invertebrates, especially in cold environments (Homburg et al 2013; Høye and Sikes 2013; Ameline et al 2017). Larger individuals show higher fecundity and lower mortality rates (Smith and Fretwell 1974; Fox and Czesak 2000)
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