Annals of Botany Page 1 of 23 doi:10.1093/aob/mcw108, available online at www.aob.oxfordjournals.org Breeding system diversification and evolution in American Poa supersect. Homalopoa (Poaceae: Poeae: Poinae) Liliana M. Giussani1,*, Lynn J. Gillespie2, M. Amalia Scataglini1,Marıa A. Negritto3, Ana M. Anton4 and Robert J. Soreng5 1Instituto de Botanica Darwinion, San Isidro, Buenos Aires, Argentina, 2Research and Collections Division, Canadian Museum of Nature, Ottawa, Ontario, Canada, 3Universidad de Magdalena, Santa Marta, Colombia, 4Instituto Multidisciplinario de Biologıa Vegetal (IMBIV), CONICET-UNC, Cordoba, Argentina and 5Department of Botany, Smithsonian Institution, Washington, DC, USA *For correspondence. E-mail
[email protected] Received: 11 December 2015 Returned for revision: 18 February 2016 Accepted: 18 March 2016 Downloaded from Background and Aims Poa subgenus Poa supersect. Homalopoa has diversified extensively in the Americas. Over half of the species in the supersection are diclinous; most of these are from the New World, while a few are from South-East Asia. Diclinism in Homalopoa can be divided into three main types: gynomonoecism, gynodioe- cism and dioecism. Here the sampling of species of New World Homalopoa is expanded to date its origin and diver- sification in North and South America and examine the evolution and origin of the breeding system diversity. Methods A total of 124 specimens were included in the matrix, of which 89 are species of Poa supersect. http://aob.oxfordjournals.org/ Homalopoa sections Acutifoliae, Anthochloa, Brizoides, Dasypoa, Dioicopoa, Dissanthelium, Homalopoa sensu lato (s.l.), Madropoa and Tovarochloa, and the informal Punapoa group. Bayesian and parsimony analyses were conducted on the data sets based on four markers: the nuclear ribosomal internal tanscribed spacer (ITS) and exter- nal transcribed spacer (ETS), and plastid trnT-L and trnL-F.