ABSTRACT
Dispersal and its evolution play a key role for population persistence in fragmented landscapes where habitat loss and fragmentation increase the cost of between-habitat movements. In such contexts, it is important to know how variation in dispersal and other traits is structured, and whether responses to landscape fragmentation are aligned with underlying dispersal-trait correlations, or dispersal syndromes. We, therefore, studied trait variation in Erigone longipalpis, a European spider species specialist of (often patchy) salt marshes. We collected spiders in two salt-marsh landscapes differing in habitat availability. We then reared lab-born spiders for two generations in controlled conditions, and measured dispersal and its association with various key traits. Erigone longipalpis population densities were lower in the more fragmented landscape. Despite this, we found no evidence of differences in dispersal, or any other trait we studied, between the two landscapes. While a dispersal syndrome was present at the among-individual level (dispersers were more fecund and faster growing, among others), there was no indication it was genetically driven: among-family differences in dispersal were not correlated with differences in other traits. Instead, we showed that the observed phenotypic covariations were mostly due to within-family correlations. We hypothesize that the dispersal syndrome is the result of asymmetric food access among siblings, leading to variation in development rates and carrying over to adult traits. Our results show we need to better understand the sources of dispersal variation and syndromes, especially when dispersal may evolve rapidly in response to environmental change.
ABSTRACT
Landscape connectivity promotes dispersal and other types of movement, including foraging activity; consequently, the inclusion of connectivity concept is a priority in conservation and landscape planning in response to fragmentation. Urban planners expect the scientific community to provide them with an easy, but scientifically rigorous, method to identify highly connecting contexts in landscapes. The least-cost paths (LCP) method is one of the simplest resistance-based models that could be a good candidate to spatially identify areas where movement is potentially favored in a given landscape. We tested the efficiency of LCP predictions to detect highly connecting landscape contexts facilitating individual movements compared to those performed in un-connecting landscape contexts. We used a landscape-level behavioral experiment based on a translocation protocol and individual repeated measures. In the city of Rennes (France), 30 male hedgehogs (Erinaceus europaeus) were translocated and radio-tracked in both highly connecting and un-connecting contexts, respectively, which were determined by the presence and absence of modelled LCPs. Individual movement patterns were compared between the two predicted contexts. Individuals travelled longer distances, moved faster, and were more active in the highly connecting contexts compared to the un-connecting contexts. Moreover, in highly connecting contexts, hedgehog movement followed LCP orientation, with individuals using more wooded habitats than other land cover class. By using a rigorous experimental design, this study validated the ecological relevance of LCP analysis to identify highly connecting areas, and could be easily implemented by urban landscape planners.
