Ephemerum cohaerens (Hedw.) Hampe, répartition et écologie en France

Ephemerum cohaerens is a widely spread species that has been mentioned in North America, Asia and Europe. In France, a bibliographical survey yielded 2 localities, the classic one of Bas-Rhin and that of Deux-Sèvres. In the present account the authors provide 5 additional localities, in the departments of Eure-et-Loir, Savoie and Isère. Ephemerum cohaerens is a strictly hygrophilous and heliophilous taxon that thrives in a great number of different habitats, the most typical one being marginal reservoir and lake mud which have been exposed after long period of submergence and also stubble fields. Ephemerum cohaerens evidently rely on sexual production of spores but asexual reproduction, by means of protonematal fragments and tubers, should also be considered in assessing its strategy. It appears that Ephemerum cohaerens is most probably a taxon that was strictly dependent upon disturbance that characterizes the natural dynamic of many habitats such as lakes or river. Adequate managing should be based on periodic disturbance of the superficial substratum layers.