Spider webs, stable isotopes and molecular gut content analysis: multiple lines of evidence support trophic niche differentiation in a community of Hawaiian spiders

1. Adaptive radiations are typically characterized by niche partitioning among their constituent species. Trophic niche partitioning is particularly important in predatory animals, which rely on limited food resources for survival. 2. We test for trophic niche partitioning in an adaptive radiation of Hawaiian Tetragnatha spiders, which have diversified in situ on the Hawaiian Islands. We focus on a community of nine species belonging to two different clades, one web building and the other actively hunting, which co-occur in wet forest on East Maui. We hypothesize that trophic niches differ significantly both 1) among species within a clade, indicating food resource partitioning, and 2) between the two clades, corresponding with their differences in foraging strategy. 3. To assess niches of the spider species, we measure a) web architecture, the structure of the hunting tool, and b) site choice, the physical placement of the web in the habitat. We then test whether differences in these p...