GARY A. POLIS INTRAGUILD PREDATION Presented by: Maria Vozzo, BIOL 7083 April 16, 2013

Mini-Biography  Education:  Ph.D., Biology, UC-Riverside, 1977  M.A., UC-Riverside, 1975  Loyola University, 1969  Professor of Ecology at University of California – Davis  Vanderbilt University  Oregon State University  Drowned in a boating accident in the Sea of Cortez while on a field expedition in 2000 Gary Allan Polis,

Field Studies “The evidence argues that actual community food webs are extraordinarily more complex than those webs cataloged by theorists. I argue that most cataloged webs are over simplified caricatures of actual communities…that they poorly represent real biological communities. Consequently, the practice of abstracting empirical regularities from such catalogs yields an inaccurate and artifactual view of trophic interactions within communities. Contrary to strong assertions by many theorists, patterns from food webs of real communities generally do not support predictions arising from dynamic and graphic models of food-web structure.” Polis 1991

Research Interests  Scorpions, spiders, desert communities  Food web complexity  Trophic Cascades  Intraguild Predation (IGP)  “The killing and eating of prey species by a predator that also can utilize the resources of those prey”  Competition and predation by species in the system Polis et al., 1989

Research Interests  Scorpions, spiders, desert communities  Food web complexity  Trophic Cascades  Intraguild Predation (IGP)  “The killing and eating of prey species by a predator that also can utilize the resources of those prey”  Competition and predation by species in the system Polis et al. 1989

Key papers Polis, G. A., C. A. Myers and R. D. Holt The ecology and evolution of intraguild predation: Potential competitors that eat each other. Annual review of ecology and systematics 20: Cited by 1118 Polis, G. A. and R. D. Holt Intraguild predation: The dynamics of complex trophic interactions. Trends in Ecology & Evolution 7: Cited by 489 Holt, R. D. and G. A. Polis A theoretical framework for intraguild predation. The American Naturalist 149: Cited by 530

Key Concepts  Omnivory: consuming resources from more than one trophic level  Competition vs. Predation  Competition theory: Resource use, coexistence, exclusion, and alternative stable states among species  Predation theory: How predators and prey persist, predator impacts on prey, oscillations among populations Polis and Holt 1992

Shared Resource (Basal prey) Intraguild Predation Polis et al. 1989

Intermediate Predator (Intraguild or IG Prey) Shared Resource (Basal prey) Intraguild Predation Polis et al. 1989

Top Predator (Intraguild or IG Predator) Intermediate Predator (Intraguild or IG Prey) Shared Resource (Basal prey) Intraguild Predation Polis et al. 1989

Top Predator (Intraguild or IG Predator) Intermediate Predator (Intraguild or IG Prey) Shared Resource (Basal prey) Intraguild Predation Polis et al. 1989

Top Predator (Intraguild or IG Predator) Intermediate Predator (Intraguild or IG Prey) Shared Resource (Basal prey) Predation Intraguild Predation Polis et al. 1989

Top Predator (Intraguild or IG Predator) Intermediate Predator (Intraguild or IG Prey) Shared Resource (Basal prey) Predation Competition Intraguild Predation Polis et al. 1989

Intraguild Predation Polis and Holt 1992

Intraguild Predation Polis and Holt 1992 Predators, Consumers & Resource (no IGP)

Intraguild Predation Polis and Holt 1992 Predators, Consumers & Resource (no IGP) IGP

Theory Holt and Polis 1997 SymbolDefinition a’Functional response of IG predator to resource α Functional response of IG predator to IG prey aFunctional response of IG prey to resource m, m’Density dependent mortality rates b, b’ Resource consumption  IG prey and IG predator reproduction β IG predator benefit from consuming IG prey

Without IGP Isocline of predator (species A) Isocline of prey (species B) Polis et al No IGP - A excludes B; IGP enhances A No IGP - priority effect; IGP - dominance by A No IGP – B excludes A; IGP – priority effect No IGP - B excludes A; IGP - coexistence Competitors coexist with no IGP; IGP A and B

Must species B be a superior competitor in order to exist in IGP? Without IGP Isocline of predator (species A) Isocline of prey (species B) Polis et al No IGP - A excludes B; IGP enhances A No IGP - priority effect; IGP - dominance by A No IGP – B excludes A; IGP – priority effect No IGP - B excludes A; IGP - coexistence Competitors coexist with no IGP; IGP A and B

IGP is ubiquitous in nature Polis et al. 1989

IGP is ubiquitous in nature Polis et al. 1989

Community Ecology Implications of IGP  Community structure  Exclusion, coexistence, alternative stable states (Polis et al. 1988, Holt and Polis 1997)  Resource use  Superior competitors (Polis et al. 1989)  Direct vs. Indirect effects (Polis and Holt 1992)  Exclude or decrease resources  Alter behavioral interactions  Trophic cascades (Polis and Holt 1992)  Predation impacts lower trophic levels

Legacy of IGP: Trophic Cascades  Addition of top predator, suppresses larvae, indirectly benefiting aphids.  Top predator addition can suppress herbivore population Rosenheim et al

Legacy of IGP: Indirect and Direct Effects Wissinger and McGrady 1993

Legacy of IGP: Indirect and Direct Effects  IG predator presence (Tramea) reduced feeding of IG prey (Erythemis)  Indirect effect (behavior)  Direct effect (consumption) Wissinger and McGrady 1993

Legacy of IGP  How is IGP influenced by other factors such as habitat structure and complexity? Janssen et al. 2007

Legacy of IGP: Community Structure, Resource Use, Trophic Cascades, and Indirect & Direct Effects Research Questions:  How does intraguild predation and habitat structure affect species interactions on an oyster reef?  Sheepshead  Mud crab-bivalve interaction  Resource survival Consumption or indirect effects?

Oyster Reef Communities  Drastic declines in oyster populations  85% loss worldwide  Oyster reefs provide vital habitat to many species Common Oyster Reef Residents SC DNR Beck et al. 2011

Intraguild Predation Sheepshead (Archosargus probatocephalus) Mud crabs Mussels (Geukensia demissa) SC DNR sms.si.edu Top Predator Intermediate Predator Basal Prey (Panopeus herbstii) Predator-Prey Interactions Trophic Cascades Holt and Polis 1997, Janssen et al. 2007

IGP and Oyster reef complexity Sheepshead Mud crabs Mussels SC DNR sms.si.edu Top Predator Intermediate Predator Basal Prey − + Low Structure Reef High Structure Reef Sheepshead Mud crabs Mussels SC DNR sms.si.edu Top Predator Intermediate Predator Basal Prey − behavioral effect consumptive effect indirect effects Vozzo et al. 2012, presentation

IGP and Community Ecology  Community structure  Resource use  Direct vs. Indirect effects  Trophic cascades “…intraguild predation is a ubiquitous and often powerful interaction central to the structure and functioning of many natural communities; closer attention to it will enrich our understanding of population and community ecology.” Polis et al. 1989

Questions? Thank you!

Citations Beck, M. W. et al Oyster reefs at risk and recommendations for conservation, restoration, and management. BioScience 61: Grawbowski, J Habitat complexity disrupts predator-prey interactions but not the trophic cascade on oyster reefs. Ecology 85: Janssen, A. et al Habitat structure affects intraguild predation. Ecology 88: Holt, R. D. and G. A. Polis A theoretical framework for intraguild predation. The American Naturalist 149: Polis, G. A Complex-trophic interactions in deserts: an empirical critique of food-web theory. The American Naturalist 138: Polis, G. A., C. A. Myers and R. D. Holt The ecology and evolution of intraguild predation: Potential competitors that eat each other. Annual review of ecology and systematics 20: Polis, G. A. and R. D. Holt Intraguild predation: The dynamics of complex trophic interactions. Trends in Ecology & Evolution 7: Rosenheim, J. A., L. R. Wilhoit and C. A. Armer Influence of intraguild predation among generalist insect predators on the suppression of an herbivore population. Oecologia 96: Saxon, Wolfgang. “Gary Allan Polis, 53, an Expert On Scorpions and Desert Ecology”. The New York Times. 01 April February polis-53-an-expert-on-scorpions-and-desert-ecology.html Wissinger, S. and J. McGrady Intraguild predation and competition between larval dragonflies: direct and indirect effects on shared prey. Ecology 74: