Partitioning of niches among four species of orb-weaving spiders in a grassland habitat.

Partitioning of niches can play an important role in structuring faunal communities. We tested the hypothesis that differences between four species of orb-weaving spiders (Araneidae) in body size and the structure and position of their webs resulted in their partitioning the available prey. The study species are sympatric in a grassland habitat and included Argiope trifasciata (Forskål), Cyclosa turbinata (Walckenaer), Mangora gibberosa (Hentz), and Neoscona arabesca (Walckenaer). The spider species differed in body size, web diameter, height of web above the ground, spacing of mesh within webs, and the type of plant to which the web was attached. The spider species had a generalist diet and captured prey of multiple trophic levels. Nevertheless, the hypothesis was supported: the spider species differed in the types of prey that they captured. Partitioning of the available prey was influenced by body size, with larger spiders capturing larger prey, but not by the structure or position of their webs. Differences between spider species in niche may reduce competitive interactions and allow them to coexist in sympatry.