Desert locusts: abundant, highly mobile solitary populations
CIRAD scientists, in collaboration with all locust control centres in West Africa, Northwest Africa, Sudan and Pakistan, and support of the FAO, organised a substantial operation to collect populations of the desert locust (Schistocerca gregaria) during remission periods. This project provided a clearer understanding of population dynamics and made it possible to determine their size during remission periods compared to during invasion periods. It was previously thought that solitary locusts only existed in small populations and were liable to extinction as a result of the arid conditions in the Sahara. The results contradicted this belief: the solitary locust populations almost all showed high genetic diversity, indicating that population levels do not fall sufficiently at the end of invasions to affect their genetic diversity and homogeneity. In fact, populations are much larger during remission periods than previously thought. These and other conclusions of this project will support invasion surveillance and prevention strategies: solitary populations, which travel fast, can very quickly discover zones in which conditions are conducive for reproduction. During remission periods, those zones must therefore be identified as soon as possible, so as to act immediately to prevent invasions.
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