2nd Place: D3127: Spider safari: Floral associations of old field Araneae

Spiders are bioindicators, and as consumers, they prey on herbivores, other predators, and sometimes even pollinators. The net result of these interactions for the plant then depends on the functional group of the prey (herbivore vs pollinator). We investigated the floral associations of flower-dwelling spiders and assessed overall prey-capture success rates in repeated field surveys in a Maryland old field. In 25 m2 plots, we recorded floral abundance, flower size, and the visitation of pollinators and spiders to flowers. We hypothesized that flowers used by spiders would differ among spider families, that flower occupancy by spiders would increase with flower size, and that spiders would be found on flowers visited by more pollinators. In early season surveys, the most abundant spiders were crab (Thomisidae) and jumping spiders (Salticidae). Crab spiders were primarily found on flowers matching their body coloration, whereas jumping spiders tended to be found on larger flowers, indicating that drivers of floral association vary among spider taxa. Flowers varied substantially in size, from Veronica arvensis (1mm diameter) to Coronilla varia (5.5 cm). Spiders were not found on flowers smaller than 1 cm (Dianthus armeria), indicating that plants bearing smaller flowers may be free from the potential effects of spider predation on pollinators. Although spider predation on flower-visiting insects was relatively rare in our surveys, the presence and activity of the spiders may impact pollinators with strong preferences for certain flowers, with consequences for foraging behavior and ecosystem services.