SPATIAL ASSOCIATION BETWEEN A SPIDER WASP AND ITS HOST IN FRAGMENTED DUNE HABITATS

Abstract

In patchily distributed habitats, species potentially occur wherever conditions are suitable or show a restricted distribution, influenced by patch quality, geometry and configuration. If patch isolation appears to be the main determinant of the species' distribution then dispersal ability is supposed to be limited. Although only scarce literature is available, dispersal limitation seems to be an important factor in determining the spatial population structure in spiders. In this paper, we document on the spatial population structure of the rare wolf spider Alopecosa fabrilis, restricted to fragmented grey dunes along the Flemish coast (Belgium) and ask whether its distribution appears to be affected by aspects of patch configuration. Simultaneously, we investigated whether the local distribution of its main parasitoid, the spider wasp Arachnospila rufa (Hymenoptera, Pompilidae) was associated with its host. Our results in- dicate that A. fabrilis shows an aggregative population structure, which is determined by the distance to nearest occupied patch, indicating that spatially correlated habitat quality probably determine its occur- rence. Although spider wasps are generally characterized as non-specialists, the almost complete covari- ation between its spatial occurrence and that of A. fabrilis, indicates that spider hunting wasps may, at least temporally and locally, show a restricted host-range. As a result, the presence of a rather generalist parasitoid is a good predictor for the presence of nocturnal and burrowing dune wolf spider.