Connectivity, habitat heterogeneity, and population persistence in Ranunculus nodiflorus, an endangered species in France.

Here, we explore the role of habitat spatial structure in the maintenance of metapopulations of Ranunculus nodiflorus. This rare species grows in puddles that can be connected occasionally by flooded corridors. We monitored five locations in the Fontainebleau forest, France, since 2002 and recorded the presence of corridors among puddles and evaluated their impact on puddle demography and plant fitness. We showed that connections increased population size, by increasing both the number of puddles occupied by the species and the density of individuals within puddles, but seemed to have no direct influence on plant fitness. We found no evidence of a large persistent soil seed bank. Natural corridors are likely to decrease the extinction probability of the populations, most probably by allowing recolonization of empty puddles after extinctions. Therefore, the preservation of corridors appears crucial for the conservation of R. nodiflorus in its natural habitat.