Percorrer por autor "Hedderson, T. A. J."
A mostrar 1 - 7 de 7
Resultados por página
Opções de ordenação
- Evolution of the major moss lineages phylogenetic analyses based on multiple gene sequences and morphologyPublication . Newton, Alice; Cox, C. J.; Duckett, J. E.; Wheeler, J. A.; Goffinet, B.; Hedderson, T. A. J.; Mishler, B. D.Evolutionary relationships of mosses are still poorly understood, with family, order, and subclass circumscription and relationships remaining especially obscure. Over the past decade, a considerable body of data has accumulated, including information on morphological, developmental, anatomical, and ultrastructural characteristics, as well as nucleotide sequences for a number of nuclear and plastid genes. We have combined data from these different sources to provide an overview of the relationships of the major lineages of mosses. We analyzed a data set that includes 33 moss species and ten outgroup taxa drawn from the liverworts, hornworts, and vascular plants. Molecular data consisted of nucleotide sequences from four DNA regions, (rbcL, trnL-trnF, rps4 and 18S). Morphological data included 41 characters of which many were derived from published anatomical and ultra-structural studies. Combining morphological and molecular data in the analyses showed that mosses, including Sphagnum, Takakia, Andreaea and Andreaeobryum, form a monophyletic group, provided improved resolution of higher level relationships, and further insight into evolutionary patterns in morphology.
- Evolution of the major moss lineages: phylogenetic analyses based on multiple gene sequences and morphologyPublication . Newton, Alice; Cox, C. J.; Duckett, J. G.; Wheeler, J. A.; Goffinet, B.; Hedderson, T. A. J.; Mishler, B. D.Evolutionary relationships of mosses are still poorly understood, with family, order, and subclass circumscription and relationships remaining especially obscure.
- Phylogenetic relationships among the ciliate arthrodontous mosses: evidence from chloroplast and nuclear DNA sequencesPublication . Cox, C. J.; Hedderson, T. A. J.Parsimony and maximum likelihood analyses of combined trnL (UAA) 5 t exon - trnF (GAA) and rps4 exon cpDNA, and 18S nrDNA sequences of 60 arthrodontous moss taxa indicate strong support for the monophyly of a clade containing the Splachnineae, Orthotrichineae, and diplolepideous alternate sub-orders. A clade including the Splachnineae, Meesiaceae and Leptobryum (Bryaceae) is similarly well supported and forms the sister group to a clade comprising the Orthotrichineae and the other diplolepideous alternate mosses. Within this latter clade a number of weil supported lineages are identified, but relationships among these remain poorly resolved. These analyses indicate that the Splachnaceous and Orthotrichaceous peristomes have been independently derived from an ancestral 'perfect' bryoid peristome.
- Phylogenetic relationships among the diplolepideous-alternate mosses (Bryidae) inferred from nuclear and chloroplast DNA sequencesPublication . Cox, C. J.; Goffinet, B.; Newton, Alice; Shaw, A. J.; Hedderson, T. A. J.The diplolepideous-alternate peristome, when most highly developed, has endostome segments attached to a basal membrane and positioned alternate to the outer exostome teeth, with cilia often present between the segments. This peristome type defines the Bryidae (sensu Vitt et al. 1998), which includes four orders: the Bryales, Leucodontales, Hypnales, and Hookeriales, of which the latter three are mainly pleurocarpous in their growth form. Chloroplast (rbcL, rps4, and trnL-trnF) and nuclear (18S rRNA) gene sequences have been analyzed using the parsimony optimality criterion to elucidate relationships among the Bryidae. The analyses strongly support the paraphyly of the Bryidae, with the Splachnidae, and possibly the Orthotrichidae, having arisen from ancestors within the Bryidae. The Leucodontales, Hypnales, and Hookeriales form a monophyletic group, as do the pleurocarpous members of the Bryidae. However, the two pleurocarpous clades are not resolved as sister groups, although their non-monophyly is not supported by the bootstrap. The phylogenetic hypothesis provides a context in which to infer evolutionary transitions in some key morphological characters relating to the peristome and the transition from the acrocarpous to pleurocarpous growth forms.
- Phylogenetic relationships of haplolepideous mosses (Dicranidae) inferred from rps4 gene sequencesPublication . Hedderson, T. A. J.; Murray, D. J.; Cox, C. J.; Nowell, T. L.The haplolepideous mosses (Dicranidae) constitute a large group of ecologically and morphologically diverse species recognised primarily by having peristome teeth with a single row of cells on the dorsal surface.
- Phylogenetic relationships within the moss family Bryaceae based on chloroplast DNA evidencePublication . Cox, C. J.; Hedderson, T. A. J.The Bryaceae are a large cosmopolitan family of mosses containing genera of considerable taxonomic difficulty. Phylogenetic relationships within the family were inferred using data from chloroplast DNA sequences (rps4 and trnL-trnF region). Parsimony and maximum likelihood optimality criteria, and Bayesian phylogenetic inference procedures were employed to reconstruct relationships. The genera Bryum and Brachymenium are not monophyletic groups. A clade comprising Plagiobryum, Acidodontium, Mielichhoferia macrocarpa, Bryum sects. Bryum, Apalodictyon, Limbata, Leucodontium, Caespiticia, Capillaria (in part: sect. Capillaria), and Brachymenium sect. Dicranobryum, is well supported in all analyses and represents a major lineage within the family. Section Dicranobryum of Brachymenium is more closely related to section Bryum than to the other sections of Brachymenium, as are Mielichhoferia macrocarpa and M. himalayana. Species of Acidodontium form a clade with Anomobryum julaceum. The grouping of species with a rosulate gametophytic growth form suggests the presence of a 'rosulate' clade similar in circumscription to the genus Rosulabryum. Mielichhoferia macrocarpa and M. himalayana are transferred to Bryum as B. porsildii and B. caucasicum, respectively.
- The bryophyta (mosses): systematic and evolutionary inferences from an rps4 gene (cpDNA) phylogenyPublication . Goffinet, B.; Cox, C. J.; Shaw, A. J.; Hedderson, T. A. J.Phylogenetic analyses of nucleotide and amino acid sequences of the chloroplast protein coding gene rps4 were performed for 225 species of mosses, representing 84%of families recognized by Vitt (1984. In: Schuster RM, ed. New manual of bryology, vol 2. Nichinan: Hattori Botanical Laboratory), under the criterion of maximum parsimony with Takakia and Sphagnum as outgroups. Most parsimonious topologies converge to a scenario wherein the Andreaeidae are monophyletic and sister to the Bryidae ( peristomate mosses), the Nematodonteae and the Buxbaumiaceae form a monophyletic lineage, the Diphysciaceae are sister to the Arthrodonteae and, within the latter, the Funarineae-Encalyptineae-Timmiaceae-Haplolepideae compose a monophyletic clade sister to remaining diplolepideous mosses. This hypothesis suggests that early in the evolution of the Arthrodonteae, two major lineages diverged, with opposite and alternate peristomes, respectively. Bootstrap support for the deep dichotomies is poor or lacking but increases when protein translations of rps4 sequences are included in the analysis. Several novel systematic hypotheses are raised, including (a) a diplolepideous rather than haplolepideous origin of the Pleurophascaceae; (b) an a nity of the Catascopiaceae with the Funariineae rather than the Bryineae; and (c) a close relationship of the Calomniaceae and Mitteniaceae to the Rhizgoniaceae. The advantages and disadvantages of a single gene phylogeny are discussed with respect to the identi®cation of polyphyletic familial or suprafamilial taxa.