Systematics Section / ASPT
Livshultz, T. , Middleton, David , Endress, Mary , Williams, J.K. .
Systematics of the subfamily Apocynoideae (Apocynaceae) and the APSA clade.
The Apocynoideae encompasses 78 genera and 822 species. While easily circumscribed on the basis of dextrorsely contorted corollas, synorganized androecium and gynoecium forming a gynostegium, porate pollen, and follicular fruit with comose seeds, it has been difficult to divide into tribes and genera. The most recent classification of Endress and Bruyns recognizes five tribes, Apocyneae, Echiteae, Mesechiteae, Malouetieae, and Wrighteae. Previous analyses show that the Apocynoideae forms a clade, the "APSA" clade, with Periplocoideae, Secamonoideae, and Asclepiadoideae (the latter three constitute the segregate family Asclepiadaceae), but relationships within this clade have remained unresolved. To investigate tribal and generic delimitations in the Apocynoideae and relationships in the APSA clade, we sequenced the chloroplast trnL intron and trnL-trnF spacer, rps16 intron, and rpL16 intron from 85 accessions representing 38 genera from all tribes of Apocynoideae and all four subfamilies of the APSA clade plus exemplars of subfamily Rauvolfioideae as outgroups. In the strict consensus of most parsimonious trees both the Apocynoideae and Wrighteae are paraphyletic with Wrightia sister to the rest of the APSA clade, indicating that its sinistrorsely contorted corolla is a
symplesiomorphy shared with the Rauvolfioideae. The Malouetieae is monophyletic if Neobracea is included. A group including all other New World Echiteae and Apocyneae, except Apocynum, plus the Australasian Parsonsia is paraphyletic to a monophyletic group of Mesechiteae. An Old World group of Apocyneae and Echiteae is also paraphyletic with a predominantly Asian clade (plus the North American Apocynum) sister to a clade comprising the African genus Oncinotis and the clade of Secamonoideae plus Asclepiadoideae. The segregate family Asclepiadaceae is thus resolved as polyphyletic with the Periplocoideae sister to the clade of Apocyneae and Secamonoideae plus Asclepiadoideae. Much of this resolution is not supported by jackknife resampling, however. Morphological characters will be incorporated to further test it.
1 - Harvard University, Arnold Arboretum, 22 Divinity Avenue, Cambridge, Massachusetts, 02138, USA
2 - Sam Houston State University, Department of Biological Sciences, Huntsville, Texas, 77340, USA
3 - University of Zurich, Institute of Systematic Botany, Zollikerstrasse 107, Zurich, 8008, Switzerland
chloroplast DNA sequence
Presentation Type: Paper
Location: Cottonwood A (Snowbird Center)
Date: Monday, August 2nd, 2004
Time: 2:00 PM