Host Plant Availability and Nest-Site Selection of the Social Spider Stegodyphus dumicola Pocock, 1898 (Eresidae)

SIMPLE SUMMARY: Choosing the right habitat is a critical decision for an animal because it influences its survival and reproduction. Spiders are abundant in all terrestrial habitats including arid habitats. They are often associated with vegetation, which provides structure for building capture webs or activities such as foraging and mating, or which provides shelter and protection. Spiders may select the plant species they live on based on attributes that facilitate these functions. Social spiders live in groups which construct communal silk nests in trees or on shrubs. Little is known about whether and how social spiders choose host plants. In this study, we investigated the use of host plants and the role of host plant features in the social spider Stegodyphus dumicola in Namibia. We found that nests were relatively more abundant on specific plant species, on which the spiders also survived better. Spider nests were relatively more abundant on plants higher than 2 m, and on plants with thorns and with a rigid structure. Our findings indicate that social spiders are found more frequently on high and rigid host plants, which provide structure for anchoring their nests and capture webs, and on thorny plants, which may provide protection from browsing animals. ABSTRACT: An animals’ habitat defines the resources that are available for its use, such as host plants or food sources, and the use of these resources are critical for optimizing fitness. Spiders are abundant in all terrestrial habitats and are often associated with vegetation, which may provide structure for anchoring capture webs, attract insect prey, or provide protective function. Social spiders construct sedentary communal silk nests on host plants, but we know little about whether and how they make nest-site decisions. We examined host plant use in relation to host plant availability in the social spider Stegodyphus dumicola Pocock, 1898 (Eresidae) across different arid biomes in Namibia and analysed the role of host plant characteristics (height, spines, scent, sturdiness) on nest occurrence. Host plant communities and densities differed between locations. Spider nests were relatively more abundant on Acacia spp., Boscia foetida, Combretum spp., Dichrostachys cinerea, Parkinsonia africana, Tarchonanthus camphoratus, and Ziziphus mucronatus, and nests survived longer on preferred plant genera Acacia, Boscia and Combretum. Spider nests were relatively more abundant on plants higher than 2 m, and on plants with thorns and with a rigid structure. Our results suggest that spiders display differential use of host plant species, and that characteristics such as rigidity and thorns confer benefits such as protection from browsing animals.