An arthropod community beyond the dry limit of plant life

Water availability, which enables plant growth and animal activity, regulates dryland ecosystem function. In hyper-arid ecosystems, rain cannot support vascular plant growth. Therefore, hyper-arid vegetation is restricted to the lower topography, where runoff accumulates. Typically, food resources originating from areas of dense vegetation are dispersed across the desert floor, enabling animal life in areas lacking vascular plant growth. However, certain regions, such as the hyper-arid upper topography, may be devoid of plant-derived food resources. The present study examined arthropod activity in the upper topography of a hyper-arid desert, in comparison with arthropod activity in the lower topography. Pitfall traps were utilized to compare arthropod activity along unvegetated ridges with activity in parallel, vegetated riverbeds. Surprisingly, the study revealed dense arthropod communities in the barren upper topography. Arthropods collected in the upper topography represented 26% of total arthropod abundance. In addition, the overlap between arthropod identity in the ridges and wadis (i.e., riverbeds) was low, and certain arthropods were strongly affiliated with the ridges. The upper topographic communities included high numbers of silverfish (Zygentoma: Lepismatidae), malachite beetles (Psiloderes), and predatory mites (Acari: Anystidae), and these arthropods were present at various life stages. It remains unclear how arthropod communities can persist in the unvegetated upper topography of the hyper-arid study area. These results raise the possibility that other food sources, independent from vascular plants, may play a significant role in the life history of hyper-arid arthropods.