Aida Shafreena Ahmad Puad

Doctoral Dissertation Announcement

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Candidate: Aida Shafreena Ahmad Puad

Degree of: Doctor of Philosophy

Department: Biological Sciences

Title: Preliminary Revision, Phylogenetics and Studies of Anatomical Variation Along an Altitudinal Gradient in the Genus Schefflera (Araliaceae) in Sabah, Malaysia

Committee:
Dr. Todd J. Barkman, Chair
Dr. Steven L. Kohler
Dr. Maarten Vonhof
Dr. Gregory M. Plunkett

Date: Friday, February 15, 2012 1:00 p.m. to 3:00 p.m.
2734 Wood Hall

Abstract:
The genus Schefflera of the ginseng family Araliaceae is a widely distributed species in the tropics of both hemispheres and is especially abundant in mountainous areas in South America and Southeast Asia. Schefflera is the largest genus in this family and is classified into 18 subgeneric groups with more than 800 species worldwide. However, Schefflera in Borneo has never been systematically studied and remains poorly understood both taxonomically and ecologically. In this study a key is provided for 36 Schefflera species in Sabah, Malaysia. Based on field study and preserved specimens, 20 new species of Schfflera are described. Previous phylogenetic work has shown that Schefflera is not a monophyletic group and there are five unrelated clades distributed throughout all the major lineages of Araliaceae. One of the clades recognized, the Asian clade, is the largest and possibly the most complex in Araliaceae with about 315 recognized species thus far. However, that study did not include any species from Borneo (except S. elliptica which is very widely distributed in Asia and S. Tomentosa that can be found in west Malesia). Thus, the phylogenetic relationships of Schefflera in Borneo, (especially in Sabah and Sarawak, Malaysia), in relation to species from throughout the genus is still uncertain. Therefore, five DNA regions (two from the nuclear genes and two from the chloroplast genes, generating a total of 233 new DNA sequences) were used to test the monophyly of Schefflera in Borneo to investigate how Schefflera taxa within Borneo related to species from other parts of Asia and to observe how well the latest treatment for Bornean taxa reflects natural groupings of species. Phylogenetic analyses showed that Schefflera in Borneo is not monophyletic but rather are comprised of multiple lineages from within the Asian clade. A well-defined comparison between the latest treatment and the result in this study could not be concluded. Leaf anatomical and morphological traits were measured along an altitudinal gradient on Mount Kinabalu to understand how these traits vary. The result of this study showed that cuticle, palisade mesophyll, leaf thickness and LMA are most strongly correlated with elevation.