Gondwanan Origin of Major Monocot Groups Inferred from Dispersal-Vicariance Analysis

Historical biogeography of major monocot groups was investigated by biogeographical analysis of a dated phylogeny including 79 of the 81 monocot families using the Angiosperm Phylogeny Group II (APG II) classification. Five major areas were used to describe the family distributions: Eurasia, North America, South America, Africa including Madagascar, and Australasia including New Guinea, New Caledonia, and New Zealand. In order to investigate the possible correspondence with continental breakup, the tree with its terminal distributions was fitted to the geological area cladogram ((Eurasia, North America), (Africa, (South America, Australasia)) and to alternative area cladograms using the TreeFitter program. The results indicated that monocot evolution is related to the comparatively late (Eocene) connection (via Antarctica) and break up of South America and Australasia, but not to the much older connections and separations of the other areas. The family phylogeny and distributions were also subjected to dispersal-vicariance analysis using the DIVA program. A prevalence of Australasia and South America among the DIVA optimizations inside core monocots (i.e., monocots excluding Acorus and Alismatales), and especially so in Liliales, Asparagales, and at deep nodes in the core monocot and commelinid phylogeny, points to a South Gondwanan origin for those major groups; South Gondwana comprises South America (at least southern South America), Antarctica, and Australasia. Africa and the Northern Hemisphere were presumably not parts of the ancestral area for core monocots and commelinids