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Plant Syst. Evol. (2003) DOI 10.1007/s00606-003-0032-z A taxonomic reassessment of the Vittiaceae (Hypnales, Bryopsida): evidence from phylogenetic analyses of combined chloroplast and nuclear sequence data A. Vanderpoorten1, B. Goffinet2, L. Hedena¨s3, C. J. Cox4, and A. J. Shaw4 1Universite´Catholique de Louvain, Unite´d’Ecologie et Bioge´ographie, Louvain-la-Neuve, Belgium 2Department of Ecology and Evolutionary Biology, University of Connecticut, CT, USA 3Swedish Museum of Natural History, Department of Gyptogamic Botany, Stockhalm, Sweden 4Department of Biology, Duke University, NC, USA Received November 29, 2001; accepted April 8, 2003 Published online: October 16, 2003 Ó Springer-Verlag 2003 Abstract. The Vittiaceae are a small family of including other Amblystegium species suggests aquatic mosses that are defined based on game- that A. serpens may be better accommodated in tophytic traits whose interpretation has led to a distinct genus. Amblystegium serpens is the type conflicting taxonomic arrangements. Phylogenetic species of Amblystegium and thus retains the analyses of two cpDNA regions, trnL-trnF and name. The other species are accommodated in atpB-rbcL, indicate that Vittia is nested within their own genus, Hygroamblystegium, including the Amblystegiaceae s. str., suggesting that the H. fluviatile, H. humile comb. nov., H. notero- family Vittiaceae should not be recognized. phyllum, H. tenax,andH. varium. Platylomella lescurii appears nested within the Thuidiaceae/Leskeaceae. This suggests that the Key words: Vittia, Platylomella, Hygroamblyste- series of character states shared by Vittia and gium, Amblystegiaceae, convergent evolution, Platylomella, including a differentiated leaf bor- aquatic mosses, ITS, atpB-rbcL spacer, trnF-trnL der, short laminal cells, stiff stems, and a thick region. costa, are convergent features that arose inde- pendently in unrelated lineages of aquatic Hyp- Unrelated plant species growing in similar nales. Within the Amblystegiaceae, phylogenetic habitats may often exhibit a similar appearance, analyses of the two cpDNA regions combined a process known as convergent evolution. In with ITS sequence data show that Hypnobartlet- fast flowing waters, plant species often have a tia, Vittia elimbata spec. nov., V. pachyloma, and suite of convergent morphological characters, V. salina, despite their strong morphological similarity to aquatic Amblystegium species, form including extensive attachment to their sub- a clade that is sister to the Drepanocladus/Pseudo- strates, increased tensile strength, increased calliergon complex. This combined clade is unre- flexibility to dissipate energy through elasticity, solved at a polytomy that includes Amblystegium and/or a streamline shape (Suren et al. 2000). serpens and a clade including all the other Mosses, which are common in running waters, Amblystegium species. The occurrence of are rarely flexible but increase strength with a A. serpens outside the strongly supported clade suite of morphological characters such as stiff A. Vanderpoorten et al.: Taxonomic reassessment of the Vittiaceae wiry stems, small thick-walled leaf cells, a strong costa, and a leaf margin composed of many costa, and often pluri-stratose leaf borders or layers of linear, thick-walled cells (Ochyra laminae (Vitt and Glime 1984). 1987a), led to a large number of alternative Due to an assumed greater exposure of the taxonomic placements. Montagne (1838) first moss gametophyte to selective environmental interpreted the taxon, with hesitation, as a pressures, much of the suprageneric classifica- member of Gymnostomum Nees and Hornsch. tion of mosses has traditionally been based on (Pottiaceae), indicating its similarity, especially sporophytic characters. However, the assump- the possession of a thickened leaf border, with tion that gametophytic characters are more Cinclidotus P. Beauv. Subsequently, Hooker labile than sporophytic ones has been chal- and Wilson (1844) transferred the taxon into lenged (e.g. Buck 1991; Buck et al. 2000; Sciaromium (Mitt.) Mitt. within the Amblys- Hedena¨s 1999, 2001, 2002). As a consequence, tegiaceae. This treatment was followed in a number of gametophytic traits were given subsequent classification systems (Vitt 1984) primacy at various taxonomic levels in recent until Ochyra (1987a) erected the monospecific moss classifications. For example, within the genus Vittia and family Vittiaceae to accom- Hypnales, the most diverse of the two orders of modate the taxon. This taxonomic position, pleurocarpous mosses, the thickness of leaf however, remained debatable, and was dis- lamina has been interpreted as an important cussed by Hedena¨s (1995) who interpreted the taxonomic character (Ochyra 1986a) to such taxon as a specialized Amblystegium with a few an extent that new species [e.g. Palustriella autapomorphies presumably connected with pluristratosa Stech and Frahm (Stech and the adaptation to growth in running water. Frahm 2001b)], genera [e.g. Donrichardsia Most recently, Buck and Goffinet (2000) and (Grout) H.A. Crum & L.E. Anderson (Crum Ochyra and Matteri (2001) retained Vittia as a and Anderson 1979), Gradsteinia Ochyra (Och- distinct genus within the Amblystegiaceae. yra 1990, Ochyra et al. 1998), Ochyraea Vana Other taxa with at least partly polystratose (Vana 1986), Richardsiopsis Ochyra (Ochyra leaf laminae and a well-defined leaf border, 1986b)] and, in some cases, families [e.g. the such as Platylomella A. L. Andrews, were also Donrichardsiaceae (Ochyra 1985) and the included in the family (Buck and Goffinet Vittiaceae (Ochyra 1987a)], have been erected 2000). to accommodate peculiar pleurocarpous aqua- In this paper, we use variation in sequences tic mosses with variously multistratose leaf from chloroplast and nuclear loci to clarify the laminae. Recent analyses of morphological phylogenetic relationships of Vittia pachyloma (Hedena¨s 1995, 1997, 1998; Ochyra and Bedn- and the recently described species, V. salina arek-Ochyra 1999; Ochyra and Vanderpoorten Hedena¨s and Munoz (Hedena¨s and Munoz 1999) and molecular data (Stech and Frahm 2002). The analysis also included other aquatic 1999, 2001a; Stech et al. 1999, Vanderpoorten Hypnales to determine whether their morpho- et al. 2001, 2002a) suggest, conversely, that logical similarities reflect common ancestry or these taxa are often extreme expressions nested convergent responses to growth in running within larger genera, including Platyhypnidium waters. Fleisch., Drepanocladus (Mu¨ll. Hal.) Roth, Hygrohypnum Lindb., and Amblystegium Material and methods Schimp. Hence, the taxonomic position of Taxon sampling. Two sampling strategies were many aquatic mosses has been an area of employed, the first to confirm the placement of controversy. For example, the peculiar game- Vittia within the Amblystegiaceae and to assess tophytic features of one such aquatic moss, familial relationships of morphologically similar Vittia pachyloma (Mont.) Ochyra (Vittiaceae), taxa. The second dataset was constructed to assess including multistratose leaf laminae, short sister group relationships within the Amblystegia- laminal cells, a strong, percurrent to excurrent ceae. Vittia and related taxa included six accessions A. Vanderpoorten et al.: Taxonomic reassessment of the Vittiaceae of V. pachyloma from different Chilean provinces; replicates, using simple taxon addition, and saving two accessions of V. salina; one accession of a no more than 20,000 trees per replicate. puzzling aquatic moss from Bolivia previously Within the Amblystegiaceae, the sample of interpreted as an extreme Amblystegium expression; closely related species allowed the use of the internal and three accessions of Platylomella lescurii (Sull.) transcribed spacers (ITS) of the 18S-26S nrDNA, in A. L. Andrews, a rheophilous moss endemic to the combination with the two cpDNA regions. The Appalachian mountains (Table 1). The inclusion of decision to combine the partitions was made after these taxa within the Amblystegiaceae was tested comparing both the topologies and the support for by sampling members of the Amblystegiaceae s. the branches as assessed by nonparametric boot- str., plus representative members of Hypnalean strapping. If a taxon was resolved as part of two families whose potential relationships with the distinct monophyletic clades supported each by Amblystegiaceae have been suggested by morpho- bootstrap proportions of 70% or higher in bootstrap logical (Hedena¨s 1995, 1998; Ochyra and Vander- analyses of individual partitions, these partitions poorten 1999) and molecular data (Vanderpoorten would be considered incongruent (Mason-Gamer et al. 2002b) (dataset 1, appendix 1). These Hyp- and Kellog 1996). In such cases, taxa causing the nalean families include the Anomodontaceae incongruence were removed from the analysis. The (Anomodon Hook. and Tayl.), Thuidiaceae (Thui- ML analyses were conducted as described above. dium Bruch and Schimp, Haplocladium Mu¨ll. Hal., Abietinella Mu¨ll. Hal., Helodium Warnst.), Hyp- Results naceae (Hypnum Hedw., Caribaeohypnum Ando and Higuchi, Ptilium De Not.), Rhytidiaceae The substitution model maximizing the likeli- (Rhytidium (Sull.) Kindb), Brachytheciaceae hood of the neighbor-joining tree derived from (Platyhypnidium), and Leskeaceae (Leskea Hedw.). the first cpDNA dataset ()lnL ¼ 5080.6074) Neckera pennata Hedw. and N. douglasii Hook., was a general time-reversible model (Rodriguez two members of the suborder Neckerineae (Brothe- et al. 1990). The rate heterogeneity among sites rus 1925, De Luna

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