Range extensions for the rare moss Plagiothecium handelii, and its transfer to the resurrected genus Ortholimnobium

Abstract

Plagiothecium handelii is newly recorded for Europe (Austria and Romania) and eastern North America (Tennessee, USA). This dainty species was previously known only from Yunnan and Sichuan Provinces, China. Morphologically, the disjunctive populations belong to a single species. A 27-taxon phylogeny of Plagiothecium based on nuclear ITS and plastid rpl16 intron DNA sequence data resolved Austrian and Chinese populations of P. handelii as sisters, in a clade with P. paleaceum, a julaceous Himalayan species with cochleariform leaves. In contrast, P. handelii is a filiform plant with distant, ovate-acuminate leaves. In sequence identity the three terminals have a similar level of variation, suggesting that the geographic disjunction between the two populations of P. handelii is quite old. Morphologically and genetically the clade is a well defined lineage (Ortholimnobium) that is transitional between Plagiothecium s.str. and Struckia. The new combinations O. paleaceum and O. handelii are made. In Europe, O. handelii should be classified as vulnerable.