Mnium orientale sp. nov. from Japan is morphologically and genetically distinct from m. hornum in Europe and North America

Authors:

• Robert Wyatt,
• Ireneusz Odrzykoski,
• Timo Koponen

Abstract

Genetic markers from horizontal starch-gel electrophoresis showed that plants of Mnium orientale n. sp. from Japan, currently referred to M. hornum, are genetically distinct from M. hornum Hedw. of Europe and North America. Plants from Japan expressed unique alleles at approximately half of the loci surveyed. In contrast, samples from Poland and the eastern United States were highly similar, differing at only a single locus. Genetic variation was low in all populations, with expected heterozygosities reaching only 5.5% in the most polymorphic populations from Japan. Genetic evidence therefore strongly supports Koponen's earlier suspicions, based on morphological and ecological differences, that the Japanese populations represent a distinct species from M. hornum of Europe and North America. Accordingly, we suggest the new name Mnium orientale for these plants, which are characterized by their smaller size, excurrent costa, more broadly decurrent leaf base, and smaller, thick-walled laminal cells. Our approach demonstrates the utility of genetic evidence in resolving taxonomic problems in wide-ranging species of bryophytes.