Introduced species often disrupt food webs in native communities, with resultant impacts on food webs in other linked communities. Stocking of Sierra Nevada lakes with non-native trout may have impacts that extend into terrestrial food webs, because the fish decrease emergence of insects from lakes, and many terrestrial animals prey on these insects. I studied several factors that may affect wolf spider and general spider abundance at alpine lakes, in order to determine if spiders are affected by introduced trout. Using a classification and regression tree I found that habitat type, classified as either low density or high density boulder, explained the most variability in wolf spider abundance, with date of sampling period next most important to explaining variability. Sampling period was first in importance for explaining variability in overall spider abundance, with habitat next most important. Presence or absence of fish only helped explain variability in overall spider abundance after the effects of sampling period, habitat, time of day, and weather were taken into consideration. Effects of trout are therefore still debatable, and may be indirect and tempered by other interspecific interactions, such as predation or competition, with other animals that are also influenced by trout presence or absence.
About Us Science Fridays Staff Corie Cann: Research Project Kate Merrick: Bio