Analysis of body size, web size, and diet in two congeneric orb-weaving spiders (Araneae: Araneidae) syntopic in Florida scrub

摘要

The yellow garden spider, Argiope auranta Lucas (Araneae: Araneidae), is widespread in North America, whereas the Florida garden spider, Argiope?orida ChamberlinandIvie (Araneae: Araneidae), is restricted to scrub habitats in the southeastern USA. Both orb-weavers occur syntopically in natve oak scrub at the Archbold Biological Staton in Highlands County, Florida. We hypothesized that female spiders of both species might have ahigh degree of dietary niche overlap because their orb-webs are located near each other, despite the fact that they may di?er in body size and webcharacteristcs. We located 180 side-by-side pairs of mature A. auranta and A. ?orida, and assigned them at random into 3 treatment groups of 60pairs each. Argiope auranta in group 1 were more heavy-bodied and longer legged than A. ?orida. In group 2, the orb-webs of both species werehung at the same height aboveground, but A. auranta webs were larger with fewer stcky spirals than those of A. ?orida. Over the course of 5 d,the 2 spider species in group 3 captured almost the same number of aerial arthropods (80 for A. auranta; 76 for A. ?orida). We identfed most prey(94%) to genus or species. Dietary niche overlap at the ordinal level was extensive (70%), but it shrank dramatcally when calculated at the generic/species level (20%). We concluded that not only were A. auranta consuming substantally larger prey than A. ?orida, but also that they were feedingon di?erent kinds of aerial insects moving through gaps in oak scrub.