Associate Professor Rowan University, United States
Habitat complexity and the spatial arrangement of habitat elements are important characteristics of ecosystems and can influence interactions between predators and prey. In addition, the size structure of predator assemblages can contribute to the occurrence of intraguild predation (IGP) where predators that share prey also consume each other. These factors may also interact to influence the outcome of predator-prey interactions. However, there are few studies that simultaneously consider how changes in the spatial arrangement of habitat elements and size differences between top and intermediate predators influence the outcome of IGP. To better understand how these factors influence IGP among aquatic insects I conducted a mesocosm experiment with a study system that included larvae of Cybister fimbriolatus (top predator), Anax junius (intermediate predator), and Sympetrum semicinctum (shared prey). The factorial treatment design included three different habitat arrangements (uniform, patchy without a corridor, or patchy with a vegetation corridor) crossed with two different size classes of the intermediate predator (large F-1 or small F-2 A. junius). The experiment was conducted across three temporal blocks with three replicates of each treatment in each block (n=9 for each treatment). Spatial habitat arrangement had no effect on the survival of any species but larger A. junius were more likely to be consumed than smaller individuals. There was also a significant temporal block effect and survival of the shared prey trended lower with each temporal block. This was likely due to warmer water temperatures as the experiment progressed. A follow-up behavioral experiment in the lab revealed that C. fimbriolatus were significantly more active than either size of A. junius but neither species significantly altered behavior as a function of spatial habitat arrangement. The results of this research further our understanding of the effects of habitat connectivity and size structure on IGP interactions and suggest that small scale alterations in habitat connectivity are not likely to significantly impact IGP interactions in these insects.
