Division of Graduate Studies

Master’s Thesis Proposal Seminar

Abstract

Phylogeny and Biogeography of the Variegata complex in the genus Tolumnia (Orchidaceae)

Jimi Sadle

The orchid genus Tolumnia comprises about thirty species endemic to the Caribbean. The relatively large size of the genus and its restricted Caribbean distribution make the group ideal for analyzing biogeographic patterns in the region. However, taxonomic issues resulting from intraspecific variation, hybridization, homoplasy in floral characters and poor taxonomic practices have led to poorly defined species concepts. This has prevented the generation of a phylogenetic hypothesis for the genus. A particularly confusing group of eight species referred to as the Variegata complex is the center of much of the difficulty. Although a phylogenetic analysis of ITS (nrDNA) and trnL-F (cpDNA) sequences supports the monophyly of the clade, neither dataset contained enough variable characters resolve the relationships of the species within the clade.

This study will clarify the systematics of the Variegata clade and use the resulting phylogeny to assess biogeographic patterns across the range of the species. A morphological cladistic analysis using vegetative and floral characters will be conducted and parsimony analysis will be used to produce a phylogenetic hypothesis for the clade. This analysis will also be used as the basis of a formal taxonomic treatment that includes species descriptions as well as a key to the species. In addition, distribution maps will be generated from field collected location data and from herbarium specimens. These maps will be used as the basis of analysis of biogeographic patterns. Coarse patterns of correlation between environmental variables and species distribution will be evaluated by creating maps that display one or more environmental characteristic and plotting species distributions onto them. Observed patterns will then be used to develop hypotheses about factors influencing the distribution of these species in the Caribbean.

Date: April 15^th, 2002 Department: Biological Sciences

Time: 2:30

Place: University Park, WC130 Major Professor: Dr. David Lee