Integrative taxonomy reveals too extensive lumping and a new species in the moss genus <i>Amphidium</i> (Bryophyta)

<p>An integrative taxonomic approach, including molecular phylogenetic reconstructions based on plastid <i>rps4-trnF</i> and nuclear ITS sequences, statistical analysis of morphological-anatomical characters, and classical taxonomy, indicates that the reduction of 13 <i>Amphidium</i> species to three in a recent morphological revision represents a case of too extensive lumping. Instead, six <i>Amphidium</i> species can be distinguished based on molecular and morphological data, the widespread <i>Amphidium lapponicum</i>, <i>A. mougeotii</i>, and <i>A. tortuosum</i>, as well as the Macaronesian endemic <i>A. curvipes</i>, the North American endemic <i>A. californicum</i>, and a newly discovered species from Central Asia (southern Siberia and northern Mongolia), <i>A. asiaticum</i> sp. nov. Diagnostic morphological characters for all six species are discussed. The present data confirm that species diversity of <i>Amphidium</i> is highest in the Holarctic, where all six species occur.</p