GARY A POLIS INTRAGUILD PREDATION Presented by Maria

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 Gary Allan Polis, 19462000 Professor of Ecology at University of California – Davis 1998 -2000 Vanderbilt University 1979 -1998 Oregon State University 1977 -1979 Drowned in a boating accident in the Sea of Cortez while on a field expedition in 2000 www. news. ucdavis. edu

Field Studies Polis 1991 “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. ”

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 system Polis et al. , 1989 and predation by species in the

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 system Polis et al. 1989 and predation by species in the

Key papers Polis, G. A. , C. A. Myers and R. D. Holt. 1989. The ecology and evolution of intraguild predation: Potential competitors that each other. Annual review of ecology and systematics 20: 297 -330. Cited by 1118 Polis, G. A. and R. D. Holt. 1992. Intraguild predation: The dynamics of complex trophic interactions. Trends in Ecology & Evolution 7: 151 -154. Cited by 489 Holt, R. D. and G. A. Polis. 1997. A theoretical framework for intraguild predation. The American Naturalist 149: 745764. 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

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

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

Intraguild Predation Polis and Holt 1992

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

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

Theory Holt and Polis 1997 Symbol Definition a’ Functional response of IG predator to resource α Functional response of IG predator to IG prey a Functional 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

Competitors coexist with no IGP; IGP A and B No IGP - A excludes B; IGP enhances A No IGP - B excludes A; IGP coexistence No IGP - priority effect; IGP - dominance by A No IGP – B excludes A; IGP – priority effect Polis et al. 1989 Without IGP Isocline of predator (species A) Isocline of prey (species B)

Competitors coexist with no IGP; IGP A and B No IGP - A excludes B; IGP enhances A No IGP - B excludes A; IGP coexistence No IGP - priority effect; IGP - dominance by A No IGP – B excludes A; IGP – priority effect Polis et al. 1989 Without IGP Isocline of predator (species A) Isocline of prey (species B) Must species B be a superior competitor in order to

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 Mc. Grady 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 Mc. Grady 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

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

IGP and Oyster reef complexity Low Structure Reef High Structure Reef Top Predator − − SC DNR + Sheepshe ad Mussel s sms. si. ed u Basal Prey SC DNR Intermedia te Predator - Mud crabs + Sheepshea d Mud + - crab s Mussel s - Intermedia te Predator + - sms. si. edu 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

Thank you! Questions?

Beck, M. W. et al. 2011. Oyster reefs at risk and recommendations for conservation, restoration, and management. Bio. Science 61: 107 -116. Grawbowski, J. 2004. Habitat complexity disrupts predator-prey interactions but not the trophic cascade on oyster reefs. Ecology 85: 995 -1004. Janssen, A. et al. 2007. Habitat structure affects intraguild predation. Ecology 88: 2713 -2719. Holt, R. D. and G. A. Polis. 1997. A theoretical framework for intraguild predation. The American Naturalist 149: 745 -764. Polis, G. A. 1991. Complex-trophic interactions in deserts: an empirical critique of food-web theory. The American Naturalist 138: 123 -155. Polis, G. A. , C. A. Myers and R. D. Holt. 1989. The ecology and evolution of intraguild predation: Potential competitors that each other. Annual review of ecology and systematics 20: 297 -330. Polis, G. A. and R. D. Holt. 1992. Intraguild predation: The dynamics of complex trophic interactions. Trends in Ecology & Evolution 7: 151 -154. Rosenheim, J. A. , L. R. Wilhoit and C. A. Armer. 1993. Influence of intraguild predation among generalist insect predators on the suppression of an herbivore population. Oecologia 96: 439 -449. Saxon, Wolfgang. “Gary Allan Polis, 53, an Expert On Scorpions and Desert Ecology”. The New York Times. 01 April 2000. 20 February 2013. < http: //www. nytimes. com/2000/04/01/us/gary-allan-polis-53 -an-expert-on-scorpions-and-desert -ecology. html>. Wissinger, S. and J. Mc. Grady. 1993. Intraguild predation and competition between larval dragonflies: direct and indirect effects on shared prey. Ecology 74: 207 -218. Citations