Abstract Detail

Systematics Section / ASPT

Fehlberg, Shannon D. [2], Ranker, Tom A. [1].

Diversification of Encelia (Asteraceae) in the Sonoran and Mojave Deserts.

The genus Encelia (Asteraceae: Heliantheae) comprises 15 species of shrubs primarily distributed in the arid lands of southwestern North America. Two species also occur in western South America: E. hispida from the Galápagos Islands and E. canescens from Perú, Chile, and Argentina. Studies based on morphological and chemical features strongly support the monophyly of Encelia. These studies also suggest a sister-group relationship with Enceliopsis + Geraea, and the division of the genus into two distinct clades on the basis of several synapomorphies. However, further resolution of relationships within Encelia is difficult because there is some morphological overlap among taxa, and the taxa undergo hybridization when sympatric. The primary goal of this study was to examine genetic diversification in the genus Encelia within the framework of geography and geologic history in order to compare phylogenies based on morphology, chloroplastic loci, and nuclear loci and discern if speciation events are correlated with putative vicariance events. Phylogenetic relationships among species of Encelia, Enceliopsis, and Geraeae were assessed using chloroplastic and nuclear DNA sequence variation. Preliminary parsimony analysis of the combined cpDNA psbA-trnH and nrDNA ITS regions resolved relationships that did not agree with those predicted on the basis of morphology and secondary chemistry. For example, Encelia nutans, historically placed in Enceliopsis but recently placed in Encelia on the basis of achene characteristics, was strongly supported as sister to Enceliopsis agrophylla and Enceliopsis covillei.

1 - University of Colorado, University Museum & Department of Ecology and Evolutionary Biology, 265 UCB, Boulder, Colorado, 80309-0265, USA
2 - University of Colorado, Department of Ecology and Evolutionary Biology, UCB 334, Boulder, Colorado, 80309-0334, USA

Keywords:
Asteraceae
phylogenetics
Encelia.

Presentation Type: Paper
Session: 3-14
Location: Cottonwood B (Snowbird Center)
Date: Monday, August 2nd, 2004
Time: 11:30 AM
Abstract ID:659