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Stochastic aggregative responses and spatial patterns of parasitism in patchy host-parasitoid interactions
1Department of Entomology, University of Maryland, 20742, College Park, MD, USA.
Oecologia
|March 18, 2017
Summary
Stochastic models reveal that parasitoid searching behavior, not just host density, influences parasitism patterns. Variability in searching time allocation can alter density-dependent parasitism, challenging deterministic models.
Area of Science:
- Ecology
- Population Dynamics
- Behavioral Ecology
Background:
- Current host-parasitoid models assume deterministic aggregative responses, potentially oversimplifying parasitism dynamics.
- These models predict density-dependent parasitism based on parasitoid aggregation in high-density host patches.
- The role of variability in parasitoid searching time allocation remains underexplored.
Purpose of the Study:
- To investigate the impact of stochasticity in parasitoid searching time allocation on spatial patterns of parasitism.
- To compare predictions from stochastic and deterministic host-parasitoid models.
- To develop a unified 'random forager' equation applicable to various predator-prey systems.
Main Methods:
- Incorporated a stochastic aggregative response into the 'random parasitoid equation'.
- Utilized simulation based on laboratory data of parasitoid behavior.
- Analyzed the relationship between searching time variability and parasitism patterns.
Main Results:
- Stochastic models produced different parasitism patterns compared to deterministic models.
- Positive aggregative responses may not yield density-dependent parasitism if searching time variability is high.
- Even 'flat' responses (no average difference in searching time) can result in various density dependencies based on variance.
Conclusions:
- Parasitoid searching time variability is crucial for understanding spatial parasitism dynamics.
- Stochastic models offer a more nuanced view of host-parasitoid interactions than deterministic ones.
- A unified 'random forager' equation may describe diverse foraging systems, including plant-herbivore interactions.
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