Spider interactions with arthropod prey and their consequences in temperate and tropical communities

Spiders are common arthropod predators in terrestrial ecosystems. They are important consumers of herbivores and detritivores, but also feed regularly on pollinators and on other spiders. This dissertation describes research into interactions between hunting spiders and their prey and the consequences of these interactions for populations of each and for other animals and plants linked to each. In a riparian community in northern California, crab spider predation on pollinating insects can limit pollination and seed production in host plants on which the spiders hunts. In adjacent forest and grassland habitats, intraguild predation may drive spatial segregation among wolf spiders. Predation among three spider species with partially overlapping distributions is hierarchically structured, such that the largest spider exerts disproportionately greater predation pressure on the mid-sized than on the smallest species. The hierarchical nature of this interaction can promote coexistence among these three species in an interaction akin to atrophic cascade. Spiders on remote islands in the South Pacific may be vulnerable to their own prey. The invasive glassy-winged sharpshooter is killing many of the spiders that attack it in French Polynesia, apparently by lethal intoxication. The outbreak and spread of this insect has already caused reductions in the range and abundance of at least one endemic spider species. With continued natural history exploration and field experimentation we can work to understand the contexts under which hunting spiders limit and are limited by their prey, and how these interactions may change with increasing human domination of earth's ecosystems.