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Predation – what is it?

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:

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Predation – what is it?

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  1. Predation – what is it? One animal kills another for food ( + - interaction ) Parasitism / Parasitoidism Herbivory

  2. Predation Any ecological process in which energy and matter flow from one species to another. One organism consumes another in the classic “+ -” interaction: carnivore herbivore parasite / parasitoid (virus, bacteria, etc) ‘cannibalism’

  3. Why do we care? 1. Predation can act as a force to structure communities. Keystone predator Trophic cascades 2. Predation can act as a mechanism for natural selection. 3. Predation can control species distribution or density. Regulation

  4. Lotka-Volterra: classic 2-species model Primary Assumptions ● all individuals represented by the average ●linear relationship between predator and prey ●no time lag in response ●exponential growth, no K

  5. Reality (Begon et al. 1996 p. 118)

  6. Gause 1934 – rotifer vs. protist unmanipulated prey refuge added “immigration”

  7. Huffaker 1958 – mites and oranges Eotetranychus sexmaculatus vs. Typhlodromus occidentalis Initial results – similar to Gause, simple systems were incapable of sustaining coexistence Coexistence was only possible with extreme environmental heterogeneity “hide and seek”

  8. II IV III Adding reality to model predictions: C.S. Holling 1959 I Individual predation rate Prey density

  9. 2 types of predator response: 1. Functional: Change in the rate of predation by an individual predator - ‘search image’ - ‘prey switching’ 2. Numerical: Increase in the total number of predators - reproduction - aggregation Holling 1959

  10. 2 types of predators: Generalists Specialists

  11. Specialist numerical response: Krebs et al. 2001

  12. Quick 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 What factors control whether predator/prey interactions are stable?

  13. Type III functional response Factors influencing stability Stabilizing Destabilizing Low predator efficiency High predator efficiency Specialist predator Generalist predator Refugia Time lags Complex systems multiple predator spp. multiple prey spp. prey switching Simple systems

  14. Summary ● Predation involves energy and matter flowing from one species into another (+ -). ● Factors that influence coexistence: predator efficiency, system complexity refugia, time lags ● Holling’s Type I, II, III curves ● Generalist vs. specialist, numerical vs. functional ● Predation can: act as an agent of selection structure communities regulate populations

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