predation – what is it?
DESCRIPTION
Predation – what is it?. One animal kills another for food ( + - interaction ). Parasitism / Parasitoidism. Herbivory. Predation. Any ecological process in which energy and matter flow from one species to another. One organism consumes another in the classic “+ -” interaction: - PowerPoint PPT PresentationTRANSCRIPT
Predation – what is it?Predation – what is it?
One animal kills another for food
( + - interaction )
One animal kills another for food
( + - interaction )
Parasitism / ParasitoidismParasitism / Parasitoidism
HerbivoryHerbivory
Any ecological process in which energy and matter flow from one species to another.
Any ecological process in which energy and matter flow from one species to another.
PredationPredation
One organism consumes another in the classic “+ -” interaction:
carnivore herbivore
parasite / parasitoid (virus, bacteria, etc)
‘cannibalism’
One organism consumes another in the classic “+ -” interaction:
carnivore herbivore
parasite / parasitoid (virus, bacteria, etc)
‘cannibalism’
Why do we care?Why do we care?
1. Predation can act as a force to structure communities.1. Predation can act as a force to structure communities.
2. Predation can act as a mechanism for natural selection.2. Predation can act as a mechanism for natural selection.
3. Predation can control species distribution or density.3. Predation can control species distribution or density.
Keystone predatorKeystone predator
RegulationRegulation
Trophic cascadesTrophic cascades
Lotka-Volterra: classic 2-species model
Primary AssumptionsPrimary Assumptions
● all individuals represented by the average● all individuals represented by the average
● linear relationship between predator and prey● linear relationship between predator and prey
● no time lag in response● no time lag in response
● exponential growth, no K● exponential growth, no K
(Begon et al. 1996 p. 118)
RealityReality
Gause 1934 – rotifer vs. protist Gause 1934 – rotifer vs. protist
unmanipulatedunmanipulated
prey refuge addedprey refuge added
“immigration”“immigration”
Huffaker 1958 – mites and oranges Huffaker 1958 – mites and oranges
Initial results – similar to Gause, simple systems
were incapable of sustaining coexistence
Initial results – similar to Gause, simple systems
were incapable of sustaining coexistence
Coexistence was only possible with extreme
environmental heterogeneity
“hide and seek”
Coexistence was only possible with extreme
environmental heterogeneity
“hide and seek”
Eotetranychus sexmaculatusvs.
Typhlodromus occidentalis
Adding reality to model predictions: C.S. Holling 1959
Adding reality to model predictions: C.S. Holling 1959
II
III IV
I
Ind
ivid
ua
l pre
dat
ion
rat
e
Prey density
2 types of predator response:2 types of predator response:
2. Numerical: Increase in the total number of predators
- reproduction- aggregation
2. Numerical: Increase in the total number of predators
- reproduction- aggregation
1. Functional: Change in the rate of predation by an individual predator - ‘search image’ - ‘prey switching’
1. Functional: Change in the rate of predation by an individual predator - ‘search image’ - ‘prey switching’
Holling 1959 Holling 1959
2 types of predators:2 types of predators:
GeneralistsGeneralists SpecialistsSpecialists
Krebs et al. 2001
Specialist numerical response:Specialist numerical response:
Quick reviewQuick review
Simple dynamics (L-V) predicts a steady cycle
This cannot be re-created empirically without interference by the investigator
In reality, we observe a wide variety of dynamics
- cycles - stability- extinction - chaos- periodic fluctuations
Simple dynamics (L-V) predicts a steady cycle
This cannot be re-created empirically without interference by the investigator
In reality, we observe a wide variety of dynamics
- cycles - stability- extinction - chaos- periodic fluctuations
What factors control whether predator/prey interactions are stable?
What factors control whether predator/prey interactions are stable?
StabilizingStabilizing
Factors influencing stabilityFactors influencing stability
DestabilizingDestabilizing
Type III functional response
RefugiaRefugiaGeneralist predatorGeneralist predator
Low predator efficiencyLow predator efficiency
Complex systems multiple predator spp. multiple prey spp. prey switching
Complex systems multiple predator spp. multiple prey spp. prey switching
Time lags Time lags
Specialist predatorSpecialist predator
High predator efficiencyHigh predator efficiency
Simple systemsSimple systems
SummarySummary
● Factors that influence coexistence:predator efficiency, system complexityrefugia, time lags
● Factors that influence coexistence:predator efficiency, system complexityrefugia, time lags
● Predation involves energy and matter flowing from one species into another (+ -).● Predation involves energy and matter flowing from one species into another (+ -).
● Holling’s Type I, II, III curves● Holling’s Type I, II, III curves
● Generalist vs. specialist, numerical vs. functional● Generalist vs. specialist, numerical vs. functional
● Predation can: act as an agent of selectionstructure communitiesregulate populations
● Predation can: act as an agent of selectionstructure communitiesregulate populations