Presentation on theme: "Effects of habitat complexity on intraguild predation and cannibalism in an assemblage of size-structured predators Shannon Carter, Baylor University,"— Presentation transcript:
Effects of habitat complexity on intraguild predation and cannibalism in an assemblage of size-structured predators Shannon Carter, Baylor University, Class of 2014 Patrick Crumrine, PhD Rowan University, Dept. of Biology Introduction ` Methods Results Discussion Acknowledgements Traditional food webs oversimplify complex community interactions Intraguild predation (IGP) occurs when two organisms competing for the same resource prey on one another IGP is common in nature, particularly among size-structured populations Existing theoretical models do not explain the ubiquity of IGP Size structure within populations and habitat complexity may explain the persistence of IGP Cybister fimbriolatus and Anax junius are common size-structured top predators in fishless ponds This study examined habitat complexity and size structure as potential factors that facilitate IGP Research Questions Does habitat complexity affect survival of predators and prey? Is IGP or cannibalism more frequent among predators? Does a predator’s feeding behavior change in the presence of other predators? Could size structure and habitat complexity allow IGP to persist in nature? Collecting in fishless ponds Organisms separated, photographed, and measured in lab Predator and habitat treatments assigned to plastic mesocosms set up in Blandy Oak Grove Predator and prey survival measured twice daily for three days Predator of each consumed prey determined by condition of prey carcass TreatmentGrouping 1Grouping 2Grouping 3Grouping 4Grouping 5Grouping 6 High Habitat Complexity Large Cybister Large Anax Large Cybister Small Anax Large Cybister Small Cybister Large Anax Small Anax Large Anax Small Cybister Small Anax Low Habitat Complexity Large Cybister Large Anax Large Cybister Small Anax Large Cybister Small Cybister Large Anax Small Anax Large Anax Small Cybister Small Anax TreatmentPredatorPrey 1Large Cybister Small Cybister Small Anax 2Large Anax Choice test experiment set up in low density mesocosms in lab Mouth parts of prey removed Survival monitored every 2 hours until each predator consumed 1 prey Thank you to Blandy Experimental Farm, the National Science Foundation, Megan Grandinetti, Amber Burgett, Whitetail Golf Resort, and Frederick County Landfill Habitat structure affected prey survival, but did not influence IGP or cannibalism Predators’ ecological roles change through their development Cannibalism and IGP are both common interactions in aquatic communities Small Cybister is preyed on more often than small Anax because its active behavior exposes it to larger predators more frequently Predators change their feeding behavior in the presence of other predators Size structure and habitat structure add complexity to communities and could help ecologists understand predator coexistence These results are significant because our understanding of community interactions informs policy regarding agroecology and wildlife conservation ANOVA P = 0.004 Prey mortality was lower at high habitat complexity because prey were able to take refuge, thereby reducing the number of encounters with predators. For large Anax and small Cybister, predation rate was dependent on the size class of the competing heterospecific predator. Predation rates for large Cybister and small Anax were unaffected by the size of the other predator Habitat complexity did not affect survival of predators. Predation rates are averaged across habitat treatments. Size structured IGP and cannibalism were both observed, and cannibalism was more frequent. Low energetic demands led to low prey mortality for the small Cybister/small Anax treatment. Low levels of IGP between large Anax/small Cybister contributed to high prey mortality Both large Anax and large Cybister consumed small Cybister first in 8 of 9 trials. Small Cybister’s high activity level exposes it to large predators more often, resulting in higher rates of predation. Predator treatment influenced frequency of cannibalism and IGP. Cannibalism seems to be a stronger interaction than IGP for both large Anax and large Cybister.