| This study is a phylogenetic, morphological and biogeographic investigation of Sisyrinchium (Iridaceae), a New World genus of approximately 140 species, and included 60 species of Sisyrinchium. I have identified morphological characters supporting eight potential sections resolved by Bayesian analyses of nuclear and chloroplast DNA markers. I examined biogeographic patterns revealed by these analyses. Loss of pollination specialization found in species at the putative area of origin, Argentina, has been proposed as key in the radiation of section Sisyrinchium (the blue-eyed grasses) throughout South America and into North America. This idea is not supported by this study. This project also compares the relative importance of the Antillean corridor and the Mesoamerican land bridge in plant dispersal to North America.; Molecular, morphological and anatomical characters support eight sectional divisions and show subgenus Ecthronema, as currently delimited, to be a basal grade of five well supported sections. Members of the basal section are yellow flowered with a single rhipidium subtended by multiple bracts, partially fused filament columns and spreading style arms, and are confined to the sub-tropical Andes of Peru and Bolivia. The blue-eyed grasses (subgenus Sisyrinchium), as currently delineated, are also paraphyletic and include a group of morphologically anomalous species presently treated as members of subgenus Ecthronema.; Based on center of diversity, MacClade character reconstruction, Bremer's ancestral area analysis, and DIVA, the genus appears to have originated in central South America, with some sections diversifying elsewhere. Several of the sections are widespread across the Americas (sections Sisyrinchium, Alesmeria, Hydastylus and Sipacapa), while other sections are geographically restricted. Section Spathirachis is restricted to the range of its specialized pollinator, a relationship that is derived within the section. Two dispersals within section Sisyrinchium into North America occurred: one through central Mexico, and another---possibly via the Antilles---that lacks any Mexican elements. Endemic species of both North and South American mountain ranges are sister to more widespread common taxa rather than to each other. Series of mountain endemics may have originated from adjacent lowland species, rather than isolates of a widespread tropical species of the ice ages.; Keywords. Sisyrinchium, Sisyrinchioideae, Iridaceae, phylogeny, character evolution, biogeography, matK, ITS. |
