Distribution patterns of Batrachium communities in Mediterranean hard waters

The greatest number of Batrachium plant-communities is reached in base-poor waters of SW Europe where most Batrachium species develop laminar leaves. In contrast, base-rich waters of the Western Mediterranean are characterized by few Batrachium communities and by the only one Batrachium species present in the area with only dissected leaves. This work focused initially on studying the water ecology of Iberian Batrachium communitiesʹ developing in hard waters in order to seek to what extend the water physical–chemical gradient determines the occurrence of heterophyllous or homophyllous-dissected species. Floristic data and water physical–chemical data were analyzed using multivariate and comparative methods. We found two main types of Batrachium communities: community of Ranunculus trichophyllus – homophyllous and dissected species–, and community of Ranunculus penicillatus – heterophyllous species–. Alkalinity degree is the main factor separating both communities. Our results of a tentative survey on Batrachium composition in hard waters in the Eastern Mediterranean showed a wider range of physical–chemical water features as well as a greater number of Batrachium species with only dissected leaves in comparison to Western Mediterranean. We conclude that high alkalinity is related to the occurrence of Batrachium communities characterized by species with only dissected leaves in both the western and eastern parts of Mediterranean Europe.