Browsing by Author "Shaw, J. A."
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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.
- Phylogenetic relationships among Sphagnum sections: Hemitheca, Isocladus, and SubsecundaPublication . Shaw, J. A.; Cox, C. J.; Boles, S. B.Sphagnum macrophyllum, S. pylaesii, and S. cyclophyllum are morphologically atypical in the genus Sphagnum and their systematic placement has been a source of controversy. The first is generally classified in the mono-specific section Isocladus, and the second as section Hemitheca. Sphagnum cyclophyllum is classified in the section Subsecunda, but several authors have hypothesized a close relationship between all three species. Nucleotide sequences from eight nuclear and chloroplast loci were obtained to test hypotheses about relationships among these taxa. Phylogenetic analyses resolve these species (along with S. microcarpum, closely related to S. cyclophyllum) in a well-supported monophyletic group within the section Subsecunda. Sphagnum macrophyllum is sister to S. cyclophyllum, S. microcarpum, and S. pylaesii. Sphagnum cyclophyllum and S. microcarpum form a clade that is sister to S. pylaesii. Two mutually monophyletic groups of populations are resolved within S. pylaesii, one including the European populations and the other including populations from eastern North America and South America. The European populations are almost identical at the nucleotide sequence level whereas the American populations are genetically diverse. Short, delicate pseudopodia; exceptionally large opercula; and an absence or near absence of pseudostomata appear to be synapomorphies for the clade containing S. macrophyllum, S. microcarpum, S. cyclophyllum, and S. pylaesii.