Etude des stratégies de reproduction du criquet pèlerin Schistocerca gregaria
(2012)
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- Authors
- Supervisors
- Hance, Thierry
- Abstract
- (en) Schistocerca gregaria (Forsk.) (Orthoptera, Acrididae) are major insect pests in Africa, particularly in the Sahelian and Sub-Sahelian regions. Usually solitary, these locusts breed when environmental and meteorological conditions are favorable, to become gregarious. Very greedy, they attack any type of crop and pasture resulting in enormous economic loss even cyclical famines in some parts of Africa. This phase polymorphism has been the subject of numerous studies to understand the basis of this phenotypic plasticity. This is primarily the result of increasing population density, which is itself linked to reproduction success. In this thesis, we analyzed the reproductive strategies of this species. Pre-copulation, copulation and post copulation behavior were studied. The results of the competitiveness of sterilized males by irradiation and normal males allowed us to understand how we can use Sterile Insects Technique (SIT) to control this species. We showed that sperm competition is closely linked with the guard behavior observed in S. gregaria. Although multiple matings of males (polygyny) determine the reproductive success and the ability to transmit its own genes to the next generation, things are less clear in females, as multiple matings (polyandry) represent a lost in time and energy. In behavioral ecology, costs and benefits could explain the evolution of behavior, especially when the benefits exceed the costs associated with this behavior. Thus, polyandry in insects can be easily explained in terms of fitness maximization. In this thesis, multiple mating is not associated with fitness benefits for females. We found no short or long-term effects. None of the life history traits investigated (i.e. female fecundity, fertility, lifespan and offspring survival) was affected by multiple matings. In this study, we have found that polyandry in S. gregaria has another interesting explanation than fitness maximization. Polyandry acts as a signal of phase shift through offspring. We showed that hatchlings of females mated once produced smaller and green offspring characteristic of the solitary form of the desert locust. In this study, we found that females mated more than two times with different males produce larger eggs, heavier and black hatchlings characteristic of gregarious phase known in S. gregaria. According to our knowledge, it is the first study that demonstrates polyandry as a determinant of phenotypic plasticity in gregarious desert locust.
- Affiliations
Citations
Dushimirimana, S. (2012). Etude des stratégies de reproduction du criquet pèlerin Schistocerca gregaria. https://hdl.handle.net/2078.5/78279