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Abstract Detail

Systematics Section

Costea, Mihai [1], Stefanovic, Sasa [2].

A story of old love-affairs separated on different continents: Systematics of Cuscuta umbellata complex (Convolvulaceae).

Cuscuta umbellata complex is one of the 15 major clades recently circumscribed in the subgenus Grammica. The group is characterized by long-pedicellate flowers arranged in umbellate inflorescences. Most of its members occur in West Indies, Mexico and the SW USA (C. umbellata, C. desmouliniana, C. lacerata, C. leptantha, C. liliputana, C. odontolepis, C. polyanthemos, C. tuberculata), but two species (C. acuta and C. membranacea) grow in South America, and one (C. hyalina) is found as a native species in India, Pakistan and Eastern to South Africa. Sequence data from the nuclear internal transcribed spacer (ITS) and the plastid trnL-F region were used to reconstruct the phylogeny and gain a better understanding of biogeography and species boundaries within this group. Discordances between phylogenies derived from plastid and nuclear data strongly suggest that at least four independent hybridization events have occurred in the evolution of this complex, rendering the relationships among its members much more complex than previously thought. One of these newly discovered reticulation events is currently known as C. umbellata var. reflexa. This hybrid is morphologically distinct from its putative parent species, C. odontolepis or C. acuta on the maternal side, and C. umbellata on the paternal side, which supports its treatment as a new species. Another variety of C. umbellata var. dubia is similar morphologically and molecularly to C. desmouliniana, which has also a hybrid origin. These intricate evolutionary histories are likely responsible for the difficulties encountered in separating morphologically some of the species (e.g. C. acuta, C. membranacea and some forms of C. umbellata) even when using scanning electron microscopy.

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Related Links:
Digital Atlas of Cuscuta

1 - Wilfrid Laurier University, Biology, 75 University Ave N, Waterloo, Ontario, N2L3C5, Canada
2 - University of Toronto at Mississauga, Biology, 3359 Mississauga Rd N, Mississauga, Ontario, L5L1C6, Canada

parasitic plants
Cuscuta umbellata complex
reticulate evolution

Presentation Type: Oral Paper:Papers for BSA Sections
Session: 66
Location: Maybird/Cliff Lodge - Level C
Date: Wednesday, July 29th, 2009
Time: 2:00 PM
Number: 66005
Abstract ID:95