Molecular assessment of seasonal fluctuation in intraguild predation and prey utilization among wolf spiders (Schizocosa spp.)

Background/Question/Methods

Generalist predators are expected to consume prey in accordance with the relative abundance of various taxa. Despite having broad diets, generalists have been shown to be capable of selective feeding wherein prey consumption is not a simple reflection of prey availability. Deviations from expected diets have been attributed to differences in prey quality, as predators can select to feed on higher quality prey to increase their fitness. Seasonal changes, in particular stressful conditions imposed during cooler months, may impact the foraging decisions made by generalist predators by creating a greater demand for quality-based foraging while simultaneously decreasing overall prey abundance and altering prey community composition. We examined patterns of consumption in the wolf spiders Schizocosa ocreata and Schizocosa stridulansover an 18 month period and quantified the availability of different prey types. Using molecular gut content analyses, we explored the relationships between prey availability, intraguild predation, and seasonal temperature patterns.

Results/Conclusions

The leaf litter layer of a deciduous forest floor experienced significant temperature fluctuations throughout our study period, and overall arthropod abundance was negatively correlated with temperature. The prey community composition varied seasonally, with collembolans and dipterans representing the most abundant food source for Schizocosa species. Molecular gut content analyses revealed selective foraging by generalist predators, with stronger deviations from non-selective feeding in cooler months than in warmer months. The frequency and direction of intraguild predation also varied seasonally, and may reflect changes in prey abundance, community composition, and foraging decisions made based on prey quality. Overall, these results reveal seasonal changes in a dynamic food web and provide insight into foraging decisions made by generalist predators.