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RESEARCH PRODUCT

Mating system adaptation in populations of Centaurea cyanus L.

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International audience; Since the 50s, the agriculture intensification in Western Europe resulted in landscape homogenizationand reduction of habitat connectivity, which in turn caused a widespread decline of farmland biological diversity.Centaurea cyanus is one of the declining “segetal species”. It is an annual and insect-pollinatedspecies with a self-incompatibility system. When the populations are small and fragmented, they mayextinct if the incompatibility system cannot evolve towards a compatibility system. A coexistence ofmixed mating system is also possible in a population.In our study, we examined the ability of C. cyanus to produce seeds by autogamy. For this purpose,three conditions were tested: 1) two plants in a cage with flies as pollinators to allow outcrossing;2) one plant by cage with flies as pollinators to force free self fertilization; and 3) one capitulumbagged by cage without flies to force self fertilization. The results confirmed that C. cyanus is aninsect-pollinated species that cannot produce seeds without pollinators. In most of the plants flowerfertilization was less than 1% under free self fertilization while some plants produced more than 6% ofseeds. Crossing by flies yielded 26% of fertilized flowers. Therefore, a low frequency of plants seemedto be partially self-compatible. It could be an advantage for the conservation of small populations, butit could change the genetic structure of the populations and modify their biology.