Systematics Section / ASPT
Marlowe, K. , Hufford, Larry .
Phylogeny and biogeography of North American Gaillardia (Asteraceae).
Gaillardia, which comprises ca. 19 species distributed in northeastern Mexico, western North America, along the Gulf Coast and in Argentina, has received considerable taxonomic attention. We use nrDNA ITS and ETS and plastid trnT-trnF to assess phylogenetic relationships in Gaillardia and explore its biogeography. There is strong support for the monophyly of Gaillardia and the sections circumscribed by Biddulph. Gaillardia comosa, G. gypsophila and G. suavis, forming section Agassizia, are sister to the rest of Gaillardia, in which the sister clades correspond to sections Gaillardia and Hollandia. The Gulf Coast G. aestivalis complex forms section Hollandia. In section Gaillardia, G. pulchella and G. aristata form a Great Plains clade sister to Texas coast G. amblyodon, and at subjacent nodes is a Mexican grade including G. henricksonii, G. powellii, G. coahuilensis, and G. mexicana. The above are sister to G. pinnatifida and G. arizonica of the Great Plains, Intermountain and Sonoran regions. Sister to the rest of the section are Sonoran and Intermountain G. turneri, G. multiceps, G. parryi, G. spathulata and G. flava. Conflicting hypotheses for the geographic origin of Gaillardia have been proposed. DIVA indicates that prior hypotheses for a Texas or Mexican origin are consistent with our phylogeny reconstructions, although equally likely ancestral areas are the Great Plains and Gulf Coast. It also indicates that vicariance led to a split between sections Hollandia and Gaillardia. Within section Gaillardia, dispersal from an ancestral Chihuahuan desert region led to expansion to the Intermountain region, and this was followed by vicariance. A later dispersal led to the disjunct distribution of G. multiceps in southeastern New Mexico and Central Arizona. Desertification of regions in northern Mexico may be associated with the speciation of the narrowly-distributed Mexican taxa.
1 - Washington State University, School of Biological Sciences, P.O. Box 644236, Pullman, Washington, 99164-4236
Presentation Type: Paper
Location: Cottonwood B (Snowbird Center)
Date: Monday, August 2nd, 2004
Time: 11:00 AM