The role of mosquito-derived nutrients from tree holes in supporting terrestrial predator communities

Adult mosquitoes emerging from aquatic habitats may provide nutrients to surrounding terrestrial environments and the predators that inhabit them. Such nutrients, termed resource subsidies, have been explored for many aquatic insect groups from lotic environments, although the specific role of mosquitoes from lentic environments has not been explored. We predicted that if mosquitoes emerging from isolated container systems, i.e., tree holes, affect the surrounding terrestrial invertebrate predators, then there would be differences in the predator communities that inhabit areas with naturally occurring tree holes compared to areas without these containers. We also predicted that predator communities would vary with distance from the tree hole. We focused on spiders as an abundant invertebrate predator that has been shown to benefit from mosquito prey.  We sampled spiders using sweep nets and pitfall traps around three tree types:  existing tree holes in deciduous trees, and deciduous and pine trees with no tree holes. At each tree we sampled along two transects at 3, 6, 9, and 12 m from the tree.  Abundance, richness, and composition of different feeding types of spiders were assessed at each location.   After sampling, we released nitrogen enriched mosquitoes from target trees used for spider sampling, with subsequent resampling of the spider communities wherein we quantified stable isotope composition to determine if different spider feeding types were benefiting from mosquitoes emerging from tree holes or non-tree hole forming trees. Our initial sampling suggested no differences in total abundance of spiders among different tree types.