Cohen, Jim , Davis, Jerrold I. .
Systematics of Lithospermum L.: Taxonomic reevaluations and morphological evolution.
Lithospermum (Boraginaceae) comprises approximately 40 species in both the Old and New Worlds, with a center of diversity in the southwestern United States and Mexico. Using 10 cpDNA regions and 15 morphological characters, a phylogeny of Lithospermum and related taxa was reconstructed to examine taxonomic boundaries and morphological evolution. Lithospermum and related New World members of the tribe Lithospermeae are a monophyletic group, with five of the genera, Lasiarrhenum, Macromeria, Nomosa, Onosmodium, and Psilolaemus, nested within Lithospermum. Of these genera, Macromeria and Onosmodium are the only ones that are not monotypic, and the former is polyphyletic, while the latter is monophyletic. The Old World species of Lithospermum are sister to the clade that includes all New World species of Lithospermum and the five related genera. In the New World clade, some characters are quite homoplastic, such as leaf venation, corolla color, and corolla shape. Of these three characters, four different types of leaf venation, five different corolla colors, and nine different corolla shapes are found in the ingroup. Other characters, including pollen shape, the presence/absence of faucal appendages, and the presence/absence and type of herkogamy, are less homoplastic and serve as useful synapormorphies for clades. The absence of faucal appendages and the presence of approach herkogamy characterize a large clade of New World Lithospermeae, while each of five different pollen shapes characterizes one or more smaller clades in the group. Because Lithospermum is not monophyletic without the inclusion of the other members of New World Lithospermeae, an updated taxonomy of the group has been proposed, and this more inclusive Lithospermum can be recognized by a combination of two characteristics: smooth, white, erect, lustrous nutlets, and corollas that are white, orange, yellow, and/or yellow-green.
Log in to add this item to your schedule
1 - Cornell University, Department of Plant Biology, 412 Mann LIbrary, Tower Road, Ithaca, NY, 14853, USA
2 - Cornell University, L.H. Bailey Hortorium, Department of Plant Biology, Ithaca, New York, 14853, USA
Presentation Type: Oral Paper:Papers for BSA Sections
Location: Cottonwood D/Snowbird Center
Date: Monday, July 27th, 2009
Time: 8:45 AM