Abstract Detail

Systematics Section/ASPT

Paudyal, Sushil [1], Delprete, Piero [2], Motley, Timothy [3].

Improved phylogenetic resolution and insight into the ancestral origin of the problematic Exostema alliance (Chiococceae; Rubiaceae).

Exostema (sensu McDowell 1996) is a Neotropical genus of 25 species of trees and shrubs. In 1998, McDowell and Bremer considered Exostema to be monophyletic. Phylogenies using molecular data have shown Exostema to be paraphyletic and polyphyletic and reveled close relationships of Coutarea and Hintonia with certain species of Exostema. Subsequently, Borhidi segregated section Pitonia from Exostema as a new genus Solenandra. Because morphology does not always correspond to the well-resolved clades because of the presence of both convergence and divergence within clades, it has been complicated to understand the taxonomic relationships. Reconstructing the biogeographical history has also been hindered by the lack of well-resolved phylogenetic trees. We reevaluated the phylogeny of Exostema alliance (Exostema, Solenandra, Coutarea, and Hintonia) using Bayesian and Maximum Likelihood analyses with data from four DNA regions (ITS, ETS, trnL-F and petD). Analyses using 26 species (over 75% of the species) yielded five distinct clades within a monophyletic complex. The two arborescent South American species of Exostema and Coutarea form a well-supported clade, while the shrubby Exostema species form two distinct clades with Solenandra nested between the two. Using RASP (Reconstruct Ancestral State in Phylogenies), a new tool for inferring ancestral state using Bayesian method, we tested the previous hypothesis suggesting a South American origin of Exostema. We find that the ancestral area reconstructions indicate the Exostema alliance more likely originated in the Greater Antilles.

Broader Impacts:

1 - Old Dominion University, Biological Sciences, 110 Mills Godwin Building, W 45th Street, Norfolk, VA, 23529, USA
2 - IRD France, Herbier de Guyane, Boite Postale 165, 97323 Cayenne Cedex, Cayenne, French Guiana
3 - Old Dominion University, Biological Sciences, 110 Mills Godwin/ W 45th St., Norfolk, VA, 23529, USA

Keywords:
biogeography
Central America
Exostema
Greater Antilles
neotropics
phylogeny
Rubiaceae
South America.

Presentation Type: Oral Paper:Papers for Sections
Session: 25
Location: Franklin A/Hyatt
Date: Tuesday, July 10th, 2012
Time: 8:15 AM
Number: 25002
Abstract ID:557