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Gregarious development in alysiine parasitoids evolved through a reduction in larval aggression
1Institute of Evolutionary and Ecological Sciences, University of Leiden
Animal Behaviour
|November 30, 1999
Summary
Siblicide in parasitoid wasps, once evolved, is hard to lose. Experiments show a behavioral shift in larvae of Aphaereta pallipes, not Aphaereta genevensis, may explain the rare loss of siblicide and evolution of gregarious development.
Area of Science:
- Evolutionary Biology
- Insect Behavior
- Population Genetics
Background:
- Population genetic models posit that siblicide, once established in parasitoid wasps, is difficult to lose, making transitions to gregarious development rare.
- Phylogenetic studies indicate gregarious development has evolved multiple times, yet the underlying mechanisms remain poorly understood.
Purpose of the Study:
- To investigate the evolutionary mechanisms of gregarious development in alysiine braconids.
- To compare oviposition behavior and larval development in two similar Aphaereta species to understand the loss of siblicide.
Main Methods:
- Comparative laboratory experiments on Aphaereta genevensis and Aphaereta pallipes using Drosophila virilis as a host.
- Observation of oviposition behavior and larval development, including dissections of superparasitized hosts.
Main Results:
- Aphaereta genevensis typically lays single eggs and exhibits siblicide, with only one larva surviving.
- Aphaereta pallipes frequently lays multiple eggs, and multiple larvae often survive due to a lack of larval aggression.
- First-instar larvae of A. genevensis kill conspecifics, while A. pallipes larvae do not, suggesting a behavioral change underlies the loss of siblicide.
Conclusions:
- A simple change in larval behavior, specifically the loss of aggression towards conspecifics, may explain the evolution of gregarious development in Aphaereta.
- Aphaereta species offer a promising model system for studying the evolution of siblicide and gregariousness.