Analysis of body size, web size, and diet in two congeneric orb-weaving spiders (Araneae: Araneidae) syntopic in Florida scrub
Abstract
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.
Resumen
La araña amarilla de jardín, Argiope aurantia Lucas (Araneae: Araneidae), está muy extendida en América del Norte, mientras que la araña de jardín de la Florida, Argiope florida Chamberlin & Ivie (Araneae: Araneidae), está restringida a hábitats de matorral en el sureste de los Estados Unidos. Ambas son tejedoras de orbes (que hacen su telararaña en forma de una espiral) que ocurren sinópticamente en el matorral de roble nativo en la Estación Biológica Archbold en Condado de Highlands, Florida. Supusimos que las arañas hembras de ambas especies podrían tener un alto grado de superposición de nichos dietéticos debido a que sus telararañas-orbes están ubicadas cerca unas de otras, a pesar del hecho de que pueden diferir en el tamaño del cuerpo y las características de la red. Localizamos 180 pares de A. aurantia y A. florida maduros viviendo lado a lado y los asignamos al azar en 3 grupos de tratamiento de 60 pares cada uno. Argiope aurantia en el grupo 1 tenía un cuerpo más pesado y patas más largas que A. florida. En el grupo 2, las redes de orbe de ambas especies se colgaron a la misma altura sobre el suelo, pero las redes de A. aurantia fueran más grandes y con menos espirales pegajosas que las de A. florida. En el transcurso de 5 días, las 2 especies de arañas del grupo 3 capturaron casi la misma cantidad de artrópodos aéreos (80 para A. aurantia; 76 para A. florida). Identificamos la mayoría de las presas (94%) a nivel de género o especie. La superposición de nichos en la dieta a nivel ordinal fue extensa (70%), pero se redujo drásticamente cuando se calculó a nivel genérico/de especie (20%). Concluimos que no solo A. aurantia consumía presas sustancialmente más grandes que A. florida, sino que también se alimentaban de diferentes clases de insectos aéreos que se movían a través de brechas en los matorrales de roble.
Key Words: predation; prey selection; niche breadth; Meloidae
View this article in BioOne https://doi.org/10.1653/024.102.0215
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