Gyrothyraceae (Marchantiophyta) — a new family for the Russian liverwort flora

Abstract

Gyrothyra underwoodiana is the only species of a peculiar monotypic family, a remarkable western North American endemic. Recent exploration has revealed Gyrothyra at the western end of the Commander-Aleutian Island Chain (Bering Island), and this is the first record of the taxon in Russia. The species was collected in four localities in various parts of the island and these findings formally emphasizes the West-North American connections of the flora of the Commander Islands. However, the distribution patterns of Gyrothyra in other Aleutians may suggest the adventive character of occurrence of the species on Bering Island. The morphological description and illustrations of G. underwoodiana based on specimens from Bering Island, as well as discussion on its ecology, morphology and distribution are provided.