Notes on some Marchantiales taxa from Rishiri Island, Japan

Abstract

Rishiri Island is located near the northernmost coast of Japan, and is of great botanical interest due to the presence of a high-altitude stratovolcano. Through our recent expeditions to this island, we provided notes on some noteworthy Marchantiales taxa. We speculated that human activities and climate changes may cause the decline or disappearance of the populations of the alpine species, such as Peltolepis quadrata, Mannia gracilis and Sauteria alpina, and allow the introduction of some species that prefer low-lying and/or man-made habitats. Since there are few reports on Japanese materials, we gave a detailed illustration of Peltolepis quadrata on its important distinguishing characters. Marchantia polymorpha L. subsp. polymorpha is reported as new to Hokkaido. The distribution and taxonomic status of Cleveaceae taxa in Japan requires further reevaluation.