36 TAXON 60 (1) • February 2011: 36–50 Olsson & al. • Neckera and Thamnobryum Neckera and Thamnobryum (Neckeraceae, Bryopsida): Paraphyletic assemblages Sanna Olsson, 1,2,6 Johannes Enroth, 3 Volker Buchbender, 1,6 Lars Hedenäs, 4 Sanna Huttunen 4,5 & Dietmar Quandt 1,6 1 Institute of Botany, Plant Phylogenetics and Phylogenomics Group, Dresden University of Technology, 01062 Dresden, Germany 2 Department of Agricultural Sciences, P.O. Box 27, 00014 University of Helsinki, Finland 3 Department of Biosciences and Botanical Museum, P.O. Box 7, 00014 University of Helsinki, Finland 4 Department of Cryptogamic Botany, Swedish Museum of Natural History, Box 50007, 104 05 Stockholm, Sweden 5 Laboratory of Genetics, Department of Biology, 20014 University of Turku, Finland 6 Nees Institute for Biodiversity of Plants, University of Bonn, Meckenheimer Allee 170, 53115 Bonn, Germany Authors for correspondence: Sanna Olsson, sanna.olsson@helsinki.fi and Dietmar Quandt, quandt@uni-bonn.de Abstract Recent phylogenetic analyses indicated that the backbone phylogeny of the pleurocarpous moss family Neckeraceae falls into three distinct clades. Here the detailed composition and phylogenetic relationships of the two major clades (the Neckera clade and the Thamnobryum clade) are analysed. The phylogenetic analyses, based on sequence data from the plastid rpl16 intron and the rps4-trnT-trnL-trnF cluster as well as the nuclear ITS1 and 2, retained this tripartition and revealed a strong biogeographic pattern, especially inside the Neckera clade. In addition, several morphological characters that have been held as unique and characteristic to a certain group of mosses and therefore valuable in taxonomic classification, were shown to be highly homoplastic and subjected to convergent evolution. Consequently, the circumscriptions of Leptodon and Thamnobryum are amended, the new genera Exsertotheca, Echinodiopsis and Thamnomalia (each with two species), and Alleniella (with ten species) are formally described and several implied nomenclatural changes are proposed, including synonymisation of Alsia with Neckera and Cryptoleptodon with Leptodon. Keywords convergent evolution; molecular phylogeny; nomenclature; pleurocarpous mosses; taxonomy INTRODUCTION With around 5000 species, pleurocarpous mosses represent the largest radiation of early land-plants that occur in nearly all terrestrial ecosystems. Typically they have a creeping, pro- fusely branching habit, and the sporophyte development takes place in the apices of short, lateral branches. This contrasts to the so-called acrocarpous condition, in which the sporophytes develop at the apices of the main shoots. As defined by Bell & al. (2007) the pleurocarpous mosses form a monophylum (“core pleurocarps”) with four orders: Hypnodendrales, Ptychomni- ales, Hookeriales and Hypnales. The moss family Neckeraceae belongs to the order Hyp- nales. The family consists of temperate and tropical taxa, with the total species number estimated to be ca. 200 (Enroth, 1994a; Olsson & al., 2009a). Most of the species are epiphytic or epi- lithic, but there are also a few aquatic (rheophytic) species. Most typically Neckeraceae are large, glossy plants that have a creep- ing stolon bearing very small leaves and tufts of rhizoids located just below the leaf insertions, and more or less frondose (rarely dendroid) stems with or without distinct stipes. The leaf cells are almost always smooth, relatively short, and the marginal cells are typically quadrate to short-rectangular in few to several rows. The sporophyte features are variable but usually fairly consistent within genera. A more detailed morphological characterisation of the Neckeraceae was provided by Olsson & al. (2009b). Ac- cording to the current classification by Goffinet & Buck (2004) the family comprises 28 genera, although detailed phylogenetic analyses based on a wider taxon sampling suggest that several of these genera, such as Homaliadelphus and Bissetia (both Miya- beaceae) or Dixonia (OPP-clade) belong elsewhere (Olsson & al., 2009a,b) and more changes in generic composition are expected. However, the most recent attempt to resolve the backbone phy- logeny and broad relationships of Neckeraceae by Olsson & al. (2009b) identified three distinct clades. As one of the three, the well defined Pinnatella clade was already the focus of a detailed study that clarified most of the taxonomic and nomenclatural aspects in this group (Olsson & al., 2010). This paper focuses on the composition, phylogenetic relationships and nomenclature of the two remaining clades, containing the largest neckeraceous genera (Neckera, Thamnobryum) that were used to denominate each clade (Olsson & al., 2009b). Members of both the Neckera and Thamnobryum clades as defined by Olsson & al. (2009b) are mainly non-Asiatic and non-tropical, although the Neckera clade includes some species which have a wide, often disjunct (possibly relict) distribution, e.g., Leptodon smithii, Forsstroemia trichomitria and F. pro- ducta. Most species of the Neckera clade sensu Olsson & al. (2009b) have a weak costa and immersed capsules with reduced peristomes and the teeth at the leaf margins are usually unicel- lular. In the Thamnobryum clade sensu Olsson & al. (2009b) the few truly tropical taxa are almost exclusively limited to South America. The members of this clade are typically fairly robust, distinctly stipitate, and have a single, at least relatively strong