Systematics Section / ASPT
Stefanovic, Sasa , Kuzmina, Maria , Costea, Mihai .
Phylogeny and biogeography of parasitic genus Cuscuta (dodders; Convolvulaceae).
Cuscuta, containing some 170-180 species, is nearly cosmopolitan in distribution and occurs in a wide range of habitats and hosts. Within this genus, three subgenera are traditionally recognized based primarily on the morphology of styles and stigmas. Previous molecular studies focused extensively on two of its largest subgenera, Grammica (~135 spp.) and Cuscuta (~30 spp.), and have delimited major groups within these taxa. However, because these studies were based on relatively fast evolving, non-coding DNA regions, the sequences were unalignable among different subgenera, thus preventing the phylogenetic comparison across the genus as a whole. In order to evaluate the current circumscription and assess the relationships among its major lineages, we conducted the first broad phylogenetic study on the entire genus Cuscuta using coding plastid and nuclear sequence data (rbcL and 26S rDNA) from a wide taxonomic sampling covering its morphological, physiological, and geographical diversity. The results indicate the presence of four well-supported clades. Two of them correspond entirely, or nearly so, to subgenera Monogyna and Grammica as traditionally defined. However, subgenus Cuscuta is found to be paraphyletic, with the South African members of this subgenus (from section Africanae) more closely related to subgenus Grammica. For a number of morphological characters, our phylogenetic results disagree with both their traditional taxonomic implications and directionality of scenarios of evolution as previously proposed. While several cases of long-distance dispersal are inferred, vicariance emerges as the most dominant biogeographical pattern for Cuscuta.
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1 - University of Toronto at Mississauga, Biology, 3359 Mississauga Rd N, Mississauga, Ontario, L5L1C6, Canada
2 - Wilfrid Laurier University, Biology, 75 University Ave N, Waterloo, Ontario, N2L3C5, Canada
Presentation Type: Oral Paper:Papers for Sections
Location: Lake Erie/Hilton
Date: Monday, July 9th, 2007
Time: 10:30 AM