Abstract Detail

Systematics Section/ASPT

Giussani, Liliana [1], Gillespie, Lynn [2], Scataglini, Amalia [1], Negritto, Maria [3], Soreng, Robert J [4].

Molecular phylogeny reveals recent rapid diversification of Poa supersect. Homalopoa in the New World .

Poa subgenus Poa supersection Homalopoa includes c. 320 species distributed worldwide and represents the most recent large radiation within the genus.  In South America Homalopoa includes c. 80 species that are morphological and reproductively diverse, including hermarphroditic, gynomonoecious, gynodioecious, dioecious, and pistillate-apomictic species.  Here we use analyses of nrDNA ITS, ETS, and plastid trnT-trnL-trnF sequence data to examine phylogenetic structure, evolution of reproductive systems, and divergence dates in supersection Homalopoa with a focus on South American species.  Although basal relationships in the Homalopoa clade are not resolved, five well-supported large subclades are recovered, of which three correspond to sects. Dioicopoa, Madropoa, and Australian Brizoides.  Dioecism appears to have evolved independently at least twice within supersect. Homalopoa, in sects. Dioicopoa and Madropoa.  The North American species Poa arachnifera is confirmed as a member of the exclusively dioecious South America sect. Dioicopoa.  The informal Andean group “Punapoa” primarily resolves as two separate clades, one corresponding to mostly dwarf pistillate-apomictic species, and the second to taller gynomonecious species.  Apart from characterizing the dwarf “Punapoa” clade, one pistillate species Poa wheeleri evolved independently in the dioecious sect. Madropoa. Gynomonoecism appears to have evolved multiple times in Homalopoa.  Origin of the major Homalopoa lineages appears to have taken place in the Pliocene, while speciation within the lineages likely occurred primarily in the Pleistocene.  

1 - Instituto de Botanica Darwinion, Labardén 200. CC 22, San Isidro, Buenos Aires, B1642HYD, Argentina
2 - Canadian Museum of Nature, Research and Collections, PO Box 3443, Station D, Ottawa, Ontario, K1P 6P4, Canada
3 - Universidad del Magdalena, Carrera 32 No. 22-08, Apartado Postal 2-1-21630, Santa Marta , D.T.C.H. , Colombia
4 - Smithsonian Institution, Department of Botany , National Museum of Natural History, Washington, DC, 20013‑7012 , USA

Keywords:
Poaceae
Poa
Homalopoa
Phylogeny
South America
Breeding System.

Presentation Type: Oral Paper:Papers for Sections
Session: 13
Location: Pines South/Boise Centre
Date: Monday, July 28th, 2014
Time: 4:30 PM
Number: 13012
Abstract ID:718
Candidate for Awards:None