What's in a Name? Disentangling the <I>Dicranum scoparium</I> Species Complex (Dicranaceae, Bryophyta)

Abstract

Dicranum is a large (ca. 90 species) and taxonomically complex moss genus. Circumscriptions and relationships of many Dicranum species remain ambiguous due to the absence of a worldwide revision and comprehensive phylogenetic analyses. In this study, we address species circumscriptions and relationships of presumed close allies within Dicranum sect. Dicranum. Molecular phylogenetic reconstructions based on five chloroplast regions and nrITS suggest a close relationship between D. bonjeanii, D. howellii, D. nipponense, D. japonicum, D. cf. lorifolium, and D. scoparium, which can be regarded as the D. scoparium species complex. In contrast, D. majus and D. polysetum, as well as D. fuscescens and D. spadiceum (former varieties of D. scoparium), are separated from the complex. Molecular data are generally congruent with the morphological species concept, but the circumscriptions of D. bonjeanii, D. japonicum, D. cf. lorifolium, and D. scoparium need further study. Most analyzed D. scoparium specimens from across its Holarctic distribution are contained in one clade (D. scoparium s. s.), but a number of North American specimens are resolved as closely related to D. japonicum and D. cf. lorifolium. Costa cross sections and characters of the leaf apex (shape, serrulation of margins) are most relevant for identifying the studied Dicranum species morphologically.