New data on the distribution, ecology and syntaxonomy of Riella macrocarpa (Riellaceae, Marchantiophyta)

In this paper, we present the first reports of liverwort Riella macrocarpa in Montenegro, Sicily, and Greece. The species has been documented as occurring in former salt pans in Montenegro and Attica, in natural brackish ponds in Sicily, and in a flooded parking area in the Peloponnese. In these environments Riella macrocarpa was found growing either in monospecific communities or associated with charophytes, green algae and a few species of vascular plants. Notes on its habitats and communities based on our personal observations are presented. New distributional data on this species seems to confirm that R. macrocarpa is widespread throughout the Mediterranean, while its sister species, R. helicophylla s.s., appears to be rarer, reported so far only in the western Mediterranean countries. The mutation of the name Rielletum helicophyllae Cirujano, Velayos et García-Mur. 1993 (to Rielletum macrocarpae Cirujano, Velayos et García-Mur. mut. Romanov et al. nom. mut. nov. ) is suggested here in agreement with the International Code of Phytosociological Nomenclature. Riella macrocarpa , already included in the Italian Red List (under R. helicophylla ), is also a candidate for inclusion in the national Red Lists of Montenegro and Greece. Although this liverwort often occurs within protected areas, monitoring and conservation efforts are essential to better understand the risks and threats that the species and its habitat face.