Elucidating distributional and ecological patterns of the rare Mediterranean-Atlantic species Petalophyllum ralfsii in Europe following its first record on the Adriatic coast (Croatia)

Abstract: Šegota, V., Rimac, A., Koletić, N., Vuković, N. & Alegro, A. 2020. Elucidating distributional and ecological patterns of the rare Mediterranean-Atlantic species Petalophyllum ralfsii in Europe following its first record on the Adriatic coast (Croatia). – Herzogia 33: 275 –290. The Mediterranean-Atlantic bryophyte Petalophyllum ralfsii was discovered on Cape Kamenjak (Istrian Peninsula) as a first record of this rare liverwort in Croatia. It was found in a partly shaded, open calcareous microhabitat within evergreen vegetation with periodically persistent humidity and low-level disturbance, which largely corresponds to other Mediterranean records. No more than a hundred localities are known in Europe, extending from the British Isles, Portugal and the Balearic Islands to Italy, Malta, Greece and Cyprus. Our analyses show that P. ralfsii prefers lower and more maritime positions on the Atlantic coast, while Mediterranean populations favour higher and more inland locations. Based on climatic data analysed, the precipitation of the wettest period largely overlaps in both geographic areas, which corresponds with the observed period, in which the species benefits from humid conditions. Moreover, frost seems to be the limiting factor determining the European distribution of the species.