Evolution and Diversification of the Hookeriales (Bryopsida) with emphasis on <em>Distichophyllum</em> (Daltoniaceae) and its allied genera

Abstract

Unbiased by human intuition in interpreting morphological criteria and by convergence of morphological traits, recent methods in molecular phylogeny is offering an independent option to guide our postulations on phylogeny. This is especially significant in evolutionary studies of mosses as morphological variations are rather limited and their phylogenetic relevance difficult to interpret. Past conflicting systems of classifications with emphasis on few morphologies on either generations of the plant life cycle has been exemplified in the Hookeriales. Recent phylogenetic studies based on DNA sequence data have repeatedly proven useful in the re-interpretation of evolutionary concepts in mosses (e.g. Huttunen et al., 2004; Olsson et al., 2009a, 2009b; Quandt et al., 2009; Sotiaux et al., 2009).<br /> In the first study, the monophyly of the Hookeriales as currently circumscribed was confirmed with a sampling size of 122 taxa and a five-gene- sequence data representing three different genomes. The previous controversial position of the Hypopterygiaceae was also resolved within the order. The relationships of the families, in the greater part, have been resolved. At the generic level, several larger genera, especially within Daltoniaceae and Pilotrichaceae, are shown to be not monophyletic. Additionally six selected morphological characters (four gametophytic and two sporophytic ones), were scored to trace their evolution by means of ancestral state reconstruction in the resulting phylogeny. The common ancestor of the Hookeriales was reconstructed as having elimbate leaves, single costa, and a conspicuously striated outer exostome base without a furrow. From the study, it shows that the selected gametophytic features flared better in defining supported clades than the sporophytic ones. The many losses and regains of the exostome furrow were interpreted as reversals. Similarly, the presence of leaf costa(e), regardless of being single or double, is clearly a case of loss and gain of structure. It points to the fact that strong costae in unicostate leaves and bicostate ones are not homologous.<br /> In Chapter 2, the phylogeny between and within genera in Daltoniaceae is inferred with the same approach as Chapter 1, but with significant increase in the sampling size within the family, especially in the genus <em>Distichophyllum</em>. This study also represents the first attempt to assess infra-generic relationships within<em> Achrophyllum </em>and<em> Calyptrochaeta</em>. The monophyly of both genera are proven but definitions of some crown species require re-evaluations. Within the core Daltoniaceae, relationships among the elimbate taxa (including <em>Ephemeropsis</em>) are generally resolved. Contrastingly, topology of the limbate taxa show various combined clades of species in <em>Daltonia, Distichophyllum </em>and<em> Leskeodon</em>, not in accordance with the traditional generic concepts. Attempt to re-organize these taxa is a major challenge. Transfers and combinations are not made without adequate statistical and known morphological supports. Similarly, no new genera are proposed in the absence of critical morphological evaluation. Nevertheless, nine new combinations are made including: <em>Beeveria microcarpos, Daltonia carinata, Da. meizhiae, Distichophyllum armatus, Leskeodon crispulus, L. ellipticum, L. fernandezianus, L. montagneanus, </em>and<em> L. rotundifolius. Distichophyllum acuminatum </em>is revived from<em> Leskeodon acuminatus </em>as the accepted name<em>. Distichophyllum decolyi, </em>and<em> D. maibarae </em>are proposed as new synonyms of<em> L. montagneanus. Distichophyllum hainanense</em> stat. nov. is elevated from a varietal level. Peristome types, particularly exostome ornamentations, are shown not useful for distinguishing genera at least in Daltoniaceae. Although considerable phylogenetic knowledge has been revealed, several significant nodes remains ambiguous. Critical generic revision is crucial to bridge the lacking morphological knowledge, especially circumscriptions of the newly recognize clades.<br /> Chapter 3 presents the outcomes of re-confirming specimens for use in the molecular phylogenetic studies. In total, 24 new distributional records of species of <em>Distichophyllum</em> and allied genera in Asia and Australasia are reported along with several illustrations of the species. For each new species record, taxonomic, biogeographic and habitat notes, where appropriate, are included. Three new synonyms (<em>Distichophyllum cucullatum</em> E.B. Bartram,<em> D. macropodum</em> Dixon, and<em> D. pullei</em> Dixon) are proposed and several probable synonymies are pointed out.<br /> The proposal to conserve the illegitimate name <em>Distichophyllum</em> with a conserved type <em>D. spathulatum</em> has been drafted and submitted to the nomenclature committee and awaits the decision and voting in the forthcoming XVIII International Botanical Congress, to be held in Melbourne, Australia, in July 2011. <br /> In conclusion, the present dissertation covers research at different levels of classification and aspects with focus on <em>Distichophyllum</em>. This includes the phylogenetic studies of the order Hookeriales and the family Daltoniaceae, as well as resolving relationships between and within several genera. At a species levels, some taxonomical puzzles are resolved along with several new species records for countries and sub-regions. Attempts were also made to untangle some nomenclatural confusion and to assess their consequences due to earlier misinterpretations. Henceforth, several essential skills have been acquired during the course of this dissertation project.