UNIVERSITY GRADUATE SCHOOL BULLETIN

ANNOUNCEMENT

Florida International University

University Graduate School

Master’s Thesis Defense

Abstract

The origin, phylogenetics and natural history of Darwiniothamnus (Asteraceae: Astereae), an endemic shrub of the Galapagos Islands

by

Nicole G. Andrus

Darwiniothamnus (Asteraceae:Astereae) is currently considered to be one of seven endemic plant genera of the Galapagos Islands, and until recently the origin, number of species, and current conservation status of this genus was unknown. The purpose of this thesis was to determine the origin and phylogenetics of Darwiniothamnus and to outline the major ecological factors influencing the conservation status of this genus.

In the first part of this study the internal transcribed spacer (ITS) region of 18-26S nuclear ribosomal DNA was sequenced in 23 representatives from the tribe Astereae (including subtribes Asterinae and Grangeinae). An additional 31 sequences from members of the same tribe were exported from the GenBank database and a phylogeny was constructed in order to test the competing hypotheses on the origin of Darwiniothamnus. This thorough phylogenetic study contained putative sister taxa from throughout South, Central and North America, Mexico and the Caribbean, and sequence data suggested that Darwiniothamnus is polyphyletic and stems from two separate introductions into the Galapagos.

These findings also demonstrate that the current taxa of Darwiniothamnus are nested within the paraphyletic Erigeron-Conyza complex, composed of 24 genera spread throughout the world. In addition, the data suggest that the current members of Darwiniothamnus ought to be regrouped within the genus Erigeron, until additional work is performed on taxonomy of this genus, and all members of the Erigeron-Conyza complex.

The second part of this study details the present conservation status of Darwiniothamnus, and includes descriptions of the current biological threats on extant populations of the genus; suggestions for the naming of potential new taxa; and hypotheses on the disjunct distribution of the genus throughout the archipelago.

Date: July 24, 2002 Department: Biological Sciences

Time: 3:00 pm Major Professor: Dr. Javier Francisco-Ortega

Place: University Park, WC 130