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The evolutionary history of the danthonioid grasses: dispersal, niche evolution and radiation in the Southern Hemisphere
Wednesday 10 October 2012, Linnean Society, London
Prof. Dr. H. Peter Linder
Institute of Systematic Botany, University of Zurich, Switzerland
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The Danthonioideae (Poaceae) include some 300 species. Although these temperate, C3 grasses are present on all continents, the greatest phylogenetic, taxonomic and ecological diversity is found on the four austral landmasses: southern Africa, Australia, New Zealand and South America. Here they are often ecologically (and economically) important, and include charismatic grasses like the Wallaby-grasses of Australia, the Snow-grasses of New Zealand and Pampas-grasses of South America. Our reconstruction of the biogeographical history indicates an African origin in the early Oligocene, with repeated dispersal across the southern oceans from the middle Miocene. Dispersal rate is largely controlled by ocean width, and disperal direction from occupied to empty terrain. The pattern of diversification on each continent is different, possibly shaped by the local palaeoclimates resulting from the interaction of local topography and global climate changes during the Pleistocene. The niche evolution in the clade is still poorly understood. Cold tolerance evolved early in this group of temperate grasses, and in many instances appears to be wider than climate ranges currently found. These "truncated niches" are possibly relicts of the colder ice-age climates, suggesting adaptation rather than migration as response to the global climate shifts. Although the evolutionary history of the group, as a typical austral clade, is gradually being elucidated, we still do not know the processes underlying the frequent long distance dispersal events, the speciation processes that generated the rich taxonomic diversity, or the selective advantages of the different leaf anatomies