Document Type



Doctor of Philosophy


Biology, Plant Systematics

Date of Defense


Graduate Advisor

Elizabeth A. Kellogg, Ph.D.


Robert Magill


Elizabeth Kellogg

Robert Magill

Peter Stevens

William Buck


The family Sematophyllaceae is probably the most diverse Hypnales in the tropics and one of the most complex and taxonomically confused. This thesis comprises three parts: 1, a micromorphological study of papilla development in Taxithelium and relatives; 2, a phylogenetic study of Taxithelium; and 3, a revision of Taxithelium subgenus Vernieri. 1. I present data on the structure and development of leaf cell papillae in different Sematophyllaceae. Two kinds of papillae are recognized. One is dome-shaped to conical tapering to a firmly rounded apex (?conical?), whereas the other presents a more flaccid, baggy appearance, and is often flat-topped and wider at the apex than at the base (?baggy?). The two types of papillae are also developmentally distinct: Conical papillae first appear as slight protrusions that gradually increase in height, whereas baggy papillae change shape as they develop. Conical papillae occur in most papillose taxa, whereas baggy papillae are present only on Taxithelium subgenus Taxithelium. 2. I constructed a molecular phylogeny using three chloroplast DNA loci, three mitochondrial DNA loci and a nuclear gene. Analyses of the loci separately and in various combinations all support the monophyly of Taxithelium, which is probably of SE Asian origin. Two major clades corresponding to subgenera were resolved within the genus. Data show that T. merrillii, T. concavum, T. pluripunctatum, T. planissimum and T. isocladum are each demonstrably monophyletic units. On the other hand, T. planum, T. nepalense and T. instratum as circumscribed today are polyphyletic. Taxithelium lindbergii can be considered monophyletic only with the inclusion of T. alare. The ho1 nuclear locus is used for the first time in bryological studies, and with promising results. 3. Taxithelium includes plants with pluripapillose leaf cells as well as plants that lack papillae. Based on this results Taxithelium is newly re-circumscribed and includes two subgenera, Taxithelium and Vernieri, that differ in papilla morphology. Detailed morphometric studies were carried out in subgenus Vernieri. Eleven are recognized, a key to identify the species is provided, as well as full descriptions, nomenclature, distribution maps, etc. One species, T. damanhurianum, is new to science and is described from Seram, Indonesia.

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