Date of Award

Winter 1997

Project Type

Dissertation

Program or Major

Plant Biology

Degree Name

Doctor of Philosophy

First Advisor

A Linn Bogle

Abstract

The Hamamelidaceae are a plant family of 31 genera and more than 140 species distributed in both the Old and New worlds. There has long been debate about the subfamilial, tribal, as well as generic, relationships within the family.

Parsimony analysis was performed to examine the relationships in the Hamamelidaceae based on morphology, and DNA sequences of the Internal Transcribed spacers (ITS) of nuclear ribosomal DNA, and the chloroplast matK gene. The morphology-based phylogeny shows weak support for all clades except for the Altingioideae, and differs greatly from the molecular phylogenies. Phylogenies based on the matK and ITS data are basically congruent. The consensus of the most parsimonious trees generated from separate analyses of the morphology, ITS and matK data sets resolves few relationships. However, the analysis using the combined data set of morphology, ITS and matK gene data resolves all suprageneric relationships of the Hamamelidaceae.

In the combined phylogeny, the first clade containing Altingia and Liquidambar is sister to the second clade including the other genera of the Hamamelidaceae, supporting the recognition of the Altingioideae. Exbucklandia and Rhodoleia form a clade, suggesting a close relationship between the two genera. Mytilaria forms its own clade, as does Disanthus. Paraphyly of Disanthus, Mytilaria and Exbucklandia does not support the combination of these genera in one subfamily. Disanthus is the immediate sister taxon to the clade of the Hamamelidoideae.

A phylogenetically annotated classification system is presented here that reflects natural relationships of the genera, facilitates communication of taxon relationships, and minimizes nomenclatural modifications. This classification system recognizes six subfamilies, and six tribes in the subfamily Hamamelidoideae: (1) Altingioideae, (2) Rhodoleioideae, (3) Exbucklandioideae, (4) Mytilarioideae, (5) Disanthoideae, and (6) Hamamelidoideae. Tribes are (1) Corylopsideae, (2) Loropetaleae Trib. Nov., (3) Hamamelideae, (4) Fothergilleae, (5) Eustimgateae, and (6) Dicorypheae Trib. Nov.

The combined phylogeny manifests that parallel evolution has occurred for several important morphological characters that have been used to classify the family, including loss of petals, wind pollination, and monoecy.

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