Browsing by Author "Buck, W. R."
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- Disentangling knots of rapid evolution: origin and diversification of the moss order HypnalesPublication . Huttunen, S.; Bell, N.; Bobrova, V. K.; Buchbender, V.; Buck, W. R.; Cox, C. J.; Goffinet, B.; Hedenäs, Lars; Ho, B. -C.; Ignatov, M. S.; Krug, M.; Kuznetsova, O.; Milyutina, I. A.; Newton, Alice; Olsson, S.; Pokorny, L.; Shaw, J. A.; Stech, M.; Troitsky, A.; Vanderpoorten, A.; Quandt, D.The Hypnales are the largest order of mosses comprising approximately 4200 species. Phylogenetic reconstruction within the group has proven to be difficult due to rapid radiation at an early stage of evolution and, consequently, relationships among clades have remained poorly resolved. We compiled data from four sequence regions, namely, nuclear ITS1–5.8S–ITS2, plastid trnL–F and rps4, and mitochondrial nad5, for 122 hypnalean species and 34 species from closely related groups. Tree topologies from both Bayesian and parsimony analyses resolve the order as monophyletic. Although inferences were made from fastevolving genes, and despite strong phylogenetic signal in the nuclear ITS1–5.8S–ITS2 data, monophyly, as well as backbone nodes within the Hypnales, remains rather poorly supported except under Bayesian inferences. Ancestral distribution based on Bayesian dispersal-vicariance analysis supports a Gondwanan origin of the Hypnales and subsequent geographical radiation in the area of the former Laurasian supercontinent. Reconstruction of historical biogeography is congruent with mainly tropical and Gondwanan distributions in the sister groups Hypnodendrales, Ptychomniales, and Hookeriales, and with the dating for the oldest pleurocarp and hypnalean fossils. We contrast groupings in the phylogenetic tree with recent classifications and other phylogenetic inferences based on molecular data, and summarise current knowledge on the evolutionary history of, and relationships among, the Hypnales.
- A new species of Leskeodon (Daltoniaceae) from EcuadorPublication . Buck, W. R.; Shaw, A. J.; Cox, C. J.Leskeodon caducifolius is described from recent collections made at a single site in a cloud forest in southern Ecuador. The species is distinctive in its small, caducous leaves and elongate, porose exothecial cells.
- Newly resolved relationships in an early land plant lineage: Bryophyta class Sphagnopsida (peat mosses)Publication . Shaw, A. J.; Cox, C. J.; Buck, W. R.; Devos, N.; Buchanan, A. M.; Cave, L.; Seppelt, R.; Shaw, B.; Larraín, J.; Andrus, R.; Greilhuber, J.; Temsch, E. M.Premise of the study : The Sphagnopsida, an early-diverging lineage of mosses (phylum Bryophyta), are morphologically and ecologically unique and have profound impacts on global climate. The Sphagnopsida are currently classifi ed in two genera, Sphagnum (peat mosses) with some 350 – 500 species and Ambuchanania with one species. An analysis of phylogenetic relationships among species and genera in the Sphagnopsida were conducted to resolve major lineages and relationships among species within the Sphagnopsida. Methods : Phylogenetic analyses of nucleotide sequences from the nuclear, plastid, and mitochondrial genomes (11 704 nucleotides total) were conducted and analyzed using maximum likelihood and Bayesian inference employing seven different substitution models of varying complexity. Key results : Phylogenetic analyses resolved three lineages within the Sphagnopsida: (1) Sphagnum sericeum , (2) S. inretortum plus Ambuchanania leucobryoides , and (3) all remaining species of Sphagnum . Sister group relationships among these three clades could not be resolved, but the phylogenetic results indicate that the highly divergent morphology of A. leucobryoides is derived within the Sphagnopsida rather than plesiomorphic. A new classifi cation is proposed for class Sphagnopsida, with one order (Sphagnales), three families, and four genera. Conclusions : The Sphagnopsida are an old lineage within the phylum Bryophyta, but the extant species of Sphagnum represent a relatively recent radiation. It is likely that additional species critical to understanding the evolution of peat mosses await discovery, especially in the southern hemisphere.
- Phylogenetic evidence of a rapid radiation of pleurocarpous mosses (Bryophyta)Publication . Shaw, A. J.; Cox, C. J.; Goffinet, B.; Buck, W. R.; Boles, S. B.Pleurocarpous mosses, characterized by lateral female gametangia and highly branched, interwoven stems, comprise three orders and some 5000 species, or almost half of all moss diversity. Recent phylogenetic analyses resolve the Ptychomniales as sister to the Hypnales plus Hookeriales. Species richness is highly asymmetric with approximately 100 Ptychomniales, 750 Hookeriales, and 4400 Hypnales. Chloroplast DNA (cpDNA) sequences were obtained to compare partitioning of molecular diversity among the orders with estimates of species richness, and to test the hypothesis that either the Hookeriales or Hypnales underwent a period (or periods) of exceptionally rapid diversification. Levels of biodiversity were quantified using explicitly historical ‘‘phylogenetic diversity’’ and nonhistorical estimates of standing sequence diversity. Diversification rates were visualized using lineage-through-time (LTT) plots, and statistical tests of alternative diversification models were performed using the methods of Paradis (1997). The effects of incomplete sampling on the shape of LTT plots and performance of statistical tests were investigated using simulated phylogenies with incomplete sampling. Despite a much larger number of accepted species, the Hypnales contain lower levels of (cpDNA) biodiversity than their sister group, the Hookeriales, based on all molecular measures. Simulations confirm previous results that incomplete sampling yields diversification patterns that appear to reflect a decreasing rate through time, even when the true phylogenies were simulated with constant rates. Comparisons between simulated results and empirical data indicate that a constant rate of diversification cannot be rejected for the Hookeriales. The Hypnales, however, appear to have undergone a period of exceptionally rapid diversification for the earliest 20% of their history.