Tracking temporal predation shifts in forest wolf spiders

As generalist predators, spiders are thought to feed opportunistically during times of low prey availability. This is complicated, however, by the inevitable temporal variability in invertebrate populations, which provides spiders access to fluctuating populations of prey over their life cycle. The primary objective of this research was to identify seasonal spider predation patterns in response to seasonal variation in availability of the three common potential prey groups: springtails (Collembola), flies (Diptera), and small crickets (Ensifera). Within a temperate deciduous forest ecosystem, located in a humid subtropical climate, prey availability was monitored and, in parallel, the dominant epigeal spiders from the genus Schizocosa (Araneae: Lycosidae) were collected for molecular gut-content analysis to characterize predation strength through time. Prey availability and predation were correlated using an electivity index to quantify temporal differences in spider preference for certain prey. Despite high variation in prey populations throughout the year, spiders fed independently of Collembola availability and unexpectedly foraged for them selectively during the winter when their populations were lowest. Therefore, temperature, rather than prey availability, was a more accurate predictor of Collembola predation frequency. In addition, spiders fed on Diptera consistently and on Ensifera seldom regardless of availability. These findings suggest that spider foraging is not frequency dependent upon their prey during all parts of the year. Molecular detection of trophic interactions in this forest system provided insight into the role of the dominant Schizocosa spiders in a complex leaf-litter foodweb, especially during the winter where there is a paucity of information concerning predator-prey interactions.