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Abstract Detail

Systematics Section / ASPT

Stuessy, Tod F. [1], Blöch, Cordula [1], Schneeweiss, Hanna [1], Villasenor, Jose Luis [2].

Molecular phylogeny, classification, and chromosomal evolution of Melampodium (Asteraceae, Heliantheae).

Melampodium L. consists of 39 species distributed throughout Mexico and Central America. It is noteworthy for its high level of chromosomal diversity with n = 9, 10, 11, 12, 14, 18, 20, 23, 24, 27, 28, 30 and 33. More than 30 years ago the genus was classified into sections and series based largely on morphological and cytological data. New information from nuclear ITS and chloroplastic matK of all species provides a test of the previous classification. Based on comparisons with other genera of Heliantheae, Melampodium appears monophyletic, with the closest relatives being Acanthospermum from Central and South America and Lecocarpus endemic to the Galapagos Islands. Most of the sections (i.e., Bibractiaria, Melampodium, Rhizomaria, and Serratura) are monophyletic except for section Alcina, with M. nutans being problematic in its affinities, and section Zarabellia, with M. longifolium and M. mimulifolium separating from M. gracile, M. microcephalum, and M. paniculatum. Within section Melampodium, the previous classification recognized five series. This structure is largely confirmed except for M. glabribracteatum, which seems best placed as a monotypic series. Melampodium linearilobum of series Melampodium is seen as a putative diploid parent of the allohexaploid M. sericeum in series Sericeum. The white-rayed complex (series Leucantha), previously hypothesized as originating from series Melampodium in eastern Mexico, appears more likely to have derived from series Cupulata in northwestern Mexico. The new phylogeny reveals x = 11 as basic within the genus. Both ascending and descending aneuploidy, followed by polyploidizations via autopolyploidy and allopolyploidy, have occurred.

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1 - University of Vienna, Department of Systematic and Evolutionary Botany, Rennweg 14, Vienna, Wien, A-1030, Austria
2 - Universidad Nacional Autonoma de Mexico, Herbario Nacional, Apdo. Postal 70-367, Mexico, D.F., 04510, Mexico

chromosome evolution
molecular phylogeny.

Presentation Type: Oral Paper:Papers for Sections
Session: CP15
Location: Lake Erie/Hilton
Date: Monday, July 9th, 2007
Time: 3:45 PM
Number: CP15010
Abstract ID:1319

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