Systematics Section / ASPT
Simpson, Beryl , McDill, Joshua , Weeks, Andrea .
Phylogeny and biogeography of Pomaria (Caesalpinieae: Caesalpinioideae: Leguminosae)..
Pomaria is a genus of 16 suffrutescent perennial legumes that have traditionally been confounded with Caesalpinia, Hoffmannseggia, or both. Our molecular analyses using ITS, trnL-trnF, and rbcL show that the species of the genus form a well-supported clade sister to the Erythrostemon group of Caesalpinia. The monophyly of the genus is supported by several morphological synapomorphies including sunken orange punctate glandular trichomes on the undersurfaces of the leaves, lateral stigmas, and the presence of complex, branched trichomes on the fruits. The genus has an interesting geographical distribution with nine species in the arid regions of Southwestern USA and Mexico, four species in the dry regions of Paraguay, Uruguay, northeastern Argentina, and southern Brazil, and three species in South Africa. Preliminary data suggest that geographically, only the South American species form a clade. The phylogeny to date suggests two exchanges between the New and Old Worlds: 1) a colonization of South Africa by ancestral North American Pomaria followed by 2) a reinvasion of the Americas by a South African ancestor. The data suggest all North American species, with the exception of P. glandulosa and P. multijuga form a clade sister to a lineage containing a basal grade of South African species and a derived clade containing the South American species and one Mexican species, P. multijuga. This Mexican species may be the sole product of northward dispersal of a South American ancestor or, alternatively, the single representative of a North American ancestor that dispersed southward into South America and radiated into the clade of endemic species there. The Pomaria biogeographic pattern differs dramatically from that of another member of the Caesalpinia generic group, Hoffmannseggia, a New World genus in which there were four independent dispersals from South America, each leading to a lineage of endemic North American species.
1 - University of Texas at Austin, Plant Resources Center and Section of Integrative Biology, 1 University Station A6720, Austin, Texas, 78712, USA
Presentation Type: Paper
Location: Cottonwood C (Snowbird Center)
Date: Monday, August 2nd, 2004
Time: 11:30 AM