The Riparian Continuum Concept: Spiders and Cross Ecosystem Subsidies Along a Stream Size Gradient

Emerging aquatic insects provide important subsidies to consumers in terrestrial ecosystems and elicit a variety of responses in riparian predator populations. Flux of aquatic insects into the riparian zone is determined by both secondary production per unit stream area and stream width, while particular insect taxa emerging are dependent on location within the river continuum as described by the river continuum concept. Riparian spider communities appear to be particularly influenced by emergence events due to their various feeding strategies and ability to track preferred prey. However, little work has been conducted on the relationship between spider groups and aquatic insect emergence patterns. We hypothesized 1) spiders using different hunting strategies will be distributed in a predictable manner along the river continuum and 2) spider biomass will correlate with aquatic insect emergence. We collected riparian spiders and emerging insects from 1st-7th order streams in central Pennsylvania during a one month period in summer 2014. Preliminary results indicate riparian predator abundance increases with aquatic insect flux; however, further data analysis is required to examine patterns in spider feeding group distributions