Systematics Section / ASPT
Morris, Julie A. , Graham, Shirley A. , Schwarzbach, Andrea E. .
Placement of the monotypic genus Didiplis within the Lythraceae.
Didiplis is a semi-aquatic monotypic genus endemic to the eastern United States. It occurs in ponds or small streams completely or partially submerged, or exposed along muddy banks. Morphological characters easily place this species within the Lythraceae; however, determination of its position within the family has long been problematic. Although it is currently accepted as a separate genus, in the past, it has been recognized in five different genera. In the only monograph of the family it was classified as a species of Peplis, and is still generally considered closely associated with Peplis and Lythrum. In this study, we used molecular characters to clarify the relationships of Didiplis by sequencing both chloroplast (atpB-rbcL intergenic spacer) and nuclear (ITS) markers for a selection of genera from across the family. The data sets were analyzed separately and combined using parsimony, maximum likelihood, and Bayesian methods. Results suggest that Didiplis is not closely related to either Peplis or Lythrum, but instead falls in a distant clade as sister to Rotala, an Afro-Asian genus with a single North American representative. Morphological characters that support this relationship and the biogeographical implications will be discussed.
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1 - Kent State University, Department of Biological Sciences, 256 Cunningham Hall, Kent, Ohio, 44242, USA
2 - Kent State University, Missouri Botanical Garden, Po Box 299, St. Louis, Missouri, 63166-0299, USA
Presentation Type: Oral Paper
Date: Tuesday, August 16th, 2005
Time: 2:45 PM