Diversity of ground-active spiders in Negev desert habitats, Israel

Abstract

Deserts, despite being extreme environments, contain multiple habitats of different productivity and vegetation structure, affecting the abundance and diversity of desert arthropods. Predatory arthropods may be exceptionally diverse where scattered vegetation provides micro-habitats, concentrations of prey, and protection from predation risk. We examined the effect of habitat differences and local vegetation structure on abundance, diversity and assemblage composition of ground-active spiders in the Negev desert, Israel. Our monthly pitfall trapping in four main habitat types – dunes, loess plain, rocky slopes and wadis (dry watercourses), collected 5937 adults of 136 species. The abundance of ground-active spiders was highest in the dunes due to two dominant species, Haplodrassus pugnans and Zodarion nitidum. Both habitat and season significantly affected species richness, which peaked in the warm season; wadis had consistently higher species richness (63–74 spp.) than other habitats (48–61 spp.). Vegetation height positively correlated with both species richness and abundance in all habitats. Spider assemblages in the same, but geographically distant, habitats were more similar than those in adjacent but different habitats. Several numerically dominant species were habitat specialists. Our results confirm the need for large- and local-scale habitat management to maintain spider diversity in the face of increasing anthropogenic threats.