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, 1946-2000
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
“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
Polis et al., 1989
and predation by species in the system
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
Polis et al. 1989
and predation by species in the system
Key papers
Polis, G. A., C. A. Myers and R. D. Holt. 1989. The ecology and
evolution of intraguild predation: Potential competitors that eat
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: 745-764.
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
Intraguild Predation
Shared Resource
(Basal prey)
Polis et al. 1989
Intraguild Predation
Intermediate
Predator
(Intraguild or
IG Prey)
Shared Resource
(Basal prey)
Polis et al. 1989
Intraguild Predation
Top Predator
(Intraguild or
IG Predator)
Intermediate
Predator
(Intraguild or
IG Prey)
Shared Resource
(Basal prey)
Polis et al. 1989
Intraguild Predation
Top Predator
(Intraguild or
IG Predator)
Intermediate
Predator
(Intraguild or
IG Prey)
Shared Resource
(Basal prey)
Polis et al. 1989
Intraguild Predation
Top Predator
(Intraguild or
IG Predator)
Predation
Intermediate
Predator
(Intraguild or
IG Prey)
Shared Resource
(Basal prey)
Polis et al. 1989
Intraguild Predation
Top Predator
(Intraguild or
IG Predator)
Predation
Competition
Shared Resource
(Basal prey)
Polis et al. 1989
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 exist in IGP?
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. 1993
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
Predator-Prey
Interactions
Trophic
Cascades
Intraguild Predation
Top Predator
SC DNR
Sheepshead (Archosargus
probatocephalus)
Intermediate
Predator
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
Top Predator
−
−
SC DNR
Sheepshead
+
Mussels
sms.si.edu
Basal Prey
SC DNR
Intermediate
Predator
Mud
crabs
-
Sheepshead
+ +
Mud
crabs
-
+
-
Mussels
-
Intermediate
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. BioScience 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 eat 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-allanpolis-53-an-expert-on-scorpions-and-desert-ecology.html>.
Wissinger, S. and J. McGrady. 1993. Intraguild predation and competition between larval dragonflies:
direct and indirect effects on shared prey. Ecology 74:207-218.
Citations