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Analysis of Body Size, Web Size, and Diet in Two Congeneric Orb-Weaving Spiders (Araneae: Araneidae) Syntopic in Florida Scrub

Carrel, James E., Deyrup, Mark
TheFlorida entomologist 2019 v.102 no.2 pp. 388-394
Argiope aurantia, arthropods, body size, diet, females, habitats, highlands, insects, shrublands, webs, Florida
The yellow garden spider, Argiope aurantia Lucas (Araneae: Araneidae), is widespread in North America, whereas the Florida garden spider, Argiope florida Chamberlin & Ivie (Araneae: Araneidae), is restricted to scrub habitats in the southeastern USA. Both orb-weavers occur syntopically in native oak scrub at the Archbold Biological Station in Highlands County, Florida. We hypothesized that female spiders of both species might have a high degree of dietary niche overlap because their orb-webs are located near each other, despite the fact that they may differ in body size and web characteristics. We located 180 side-by-side pairs of mature A. aurantia and A. florida, and assigned them at random into 3 treatment groups of 60 pairs each. Argiope aurantia in group 1 were more heavy-bodied and longer legged than A. florida. In group 2, the orb-webs of both species were hung at the same height aboveground, but A. aurantia webs were larger with fewer sticky spirals than those of A. florida. Over the course of 5 d, the 2 spider species in group 3 captured almost the same number of aerial arthropods (80 for A. aurantia; 76 for A. florida). We identified most prey (94%) to genus or species. Dietary niche overlap at the ordinal level was extensive (70%), but it shrank dramatically when calculated at the generic/ species level (20%). We concluded that not only were A. aurantia consuming substantially larger prey than A. florida, but also that they were feeding on different kinds of aerial insects moving through gaps in oak scrub.