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Competitive interactions between parasitoid larvae and the evolution of gregarious development.
John J Pexton1, Peter J Mayhew
1Department of Biology, University of York, PO Box 373, YO10 5 YW, York, UK.
Oecologia
|July 20, 2004
Summary
Gregarious development in parasitoid wasps likely evolved due to reduced larval mobility, not reduced fighting. Experiments with Aphaereta species support new models, showing mobility differences explain competitive outcomes in gregarious evolution.
Area of Science:
- Evolutionary Biology
- Insect Behavior
- Parasitoid Ecology
Background:
- Gregarious development in parasitoid wasps is thought to evolve rarely due to siblicide.
- Previous models suggested gregariousness arises from non-fighting larvae, making its evolution difficult.
Purpose of the Study:
- To investigate the evolutionary drivers of gregarious development in alysiine braconid wasps.
- To test predictions of older tolerance models versus newer reduced mobility models.
Main Methods:
- Comparative study of two closely related alysiine braconid species: Aphaereta genevensis (solitary) and Aphaereta pallipes (gregarious).
- Observation of larval mobility and interspecific competition outcomes under multiparasitism.
- Experimental manipulation of host exposure to different parasitoid species.
Main Results:
- Solitary A. genevensis larvae exhibited significantly higher mobility than gregarious A. pallipes larvae.
- The proportion of hosts yielding solitary wasps decreased when exposed to gregarious wasps first.
- Observed competitive outcomes contradicted predictions based on larval fighting ability.
Conclusions:
- Reduced larval mobility, rather than a lack of fighting ability, is a more likely driver for the evolution of gregariousness in this wasp subfamily.
- Findings support newer theoretical models emphasizing larval mobility differences in gregarious evolution.