Systematics Section / ASPT
Kimball, Rebecca T. , Crawford, Daniel J. , Lowrey, Tim .
A Molecular Study of Brachylaena (Asteraceae): Phylogenetic and Biogeographic Insights.
The Afro-Madagascan genus Brachylaena, together with the very similar genus Tarchonanthus, consists of dioecious shrubs or trees. Prior molecular studies have demonstrated that the two genera comprise a strongly supported clade, though their position within the Asteraceae remains uncertain. There have been no phylogenetic studies of relationships within and between the genera. The present study used both nuclear (ITS and ETS) and plastid (rpl16) sequences to construct phylogenies for 10 of the 11 species generally recognized for Brachylaena; one accession of Tarchonanthus was also included in the ingroup because there has been considerable debate on whether the two genera should be combined or recognized as distinct. Hecastocleis shockleyi and Oldenburgia grandis were used as outgroups. Phylogenies from nuclear and plastid sequences are highly congruent, and the phylogeny generated from the combined data is well resolved with high support for most clades. The species of Brachylaena occur in two major clades, one clade includes only African taxa, with the one accession of Tarchonanthus nested within this group. The other major clade contains only species endemic to Madagascar with the notable exception of B. huillensis, a species widely distributed in southern Africa. The morphological similarity between B. huillensis and B. merana of Madagascar has been noted by others; the two species occur together in a strongly supported clade. The present study indicates that Brachylaena as traditionally recognized is paraphyletic, with Tarchonanthus nested within it. Another salient result of our study is that there appears to have been a relatively recent dispersal of B. huillensis (or an ancestor of it) from Madagascar to Africa subsequent to diversification of Brachylaena in Madagascar.
1 - University of Kansas, Dept. Ecol. & Evol. Biol. and Natural History Museum, 1200 Sunnyside Ave., Lawrence, Kansas, 66045-7534, USA
2 - University of Florida, Department of Zoology, P.O. Box 118525, 223 Bartram Hall, Gainesville, Florida, 32611-8525, USA
3 - University of New Mexico, Department of Biology, 167 Castetter Hall, Albuquerque, New Mexico, 87131-0001, USA
Presentation Type: Paper
Location: Cottonwood A (Snowbird Center)
Date: Wednesday, August 4th, 2004
Time: 12:15 PM