Biological causes of cornflower regression

International audience; Agroecosystems are currently experiencing high biodiversity loss. This decline results from intensive cropping systems. However, not all the anciently present weeds respond similarly. There should be specific biological traits that render some species more prone to disappear from arable fields than others. Investigating the biological causes of regression could inform about management strategies in changing agricultural farming systems. In this report we focus on cornflower (Centaurea cyanus) that is an emblem of the flora associated with traditional cereals in Europe. It is currently disappearing from Western regions. Several traits were investigated as seed longevity in the soil, establishment capacity and mating system. Special emphasis is given to self-incompatibility and requirement of cross-pollination by insects, which, in conjunction to the decline of the pollinator insects, results in a concurrence of un-adapted biological characteristics. However, some self-compatible individual could occur and be selected in case of small population size and shortage of pollinators. This “recue” process is at fitness cost due to inbreeding depression, which again could contribute to cornflower regression. The consequences in terms of ecosystemic services provided by such a segetal species are discussed.