Comparative spatial patterns of the terrestrial isopod Hemilepistus reaumuri at multiple scales

Previous long-term studies of the spatial distribution of Hemilepistus reaumuri at the slope scale in the Negev Desert, Israel demonstrate a high correlation between geological formation and burrow density. We explain this pattern by the difference in rock-to-soil ratio and the generation of runoff on a small scale. Areas with high rock-to-soil ratio have greater amounts of local runoff and higher densities of the isopods. Our current study examines the pattern of settlers on a patch scale, a slope scale, and a watershed scale. We use geostatistics and point pattern analysis to characterize the pattern of isopods at these different spatial scales. Our results show nonrandom spatial distributions at all scales. The pattern of settlement at the watershed scale appears to be related to expected overall water balance, which is comprised of dewfall and rainfall. The slope scale shows a relationship between the surface properties and settlement areas. The pattern at the patch scale is related to the local source-sink relationships of waterflow between the patch and the surrounding environment. By analyzing the spatial pattern at several scales we were able to show that different processes are probably determining site selection in H. reaumuri.