Systematics/Phytogeography / Taxonomie/ Section
Simon, Marcelo F. , Grether, Rosaura , Queiroz, Luciano P. de , Skema, Cynthia , Pennington, Toby , Hughes, Colin E. .
Origins and diversification of the Cerrado flora in Brazil: evidence from multiple time-calibrated molecular phylogenies.
Tropical savannas are dominated by grasses and characterized by the occurrence of frequent natural fires. It has been suggested that the floristically diverse and endemic-rich Cerrado, a savanna biome covering more than two million km2 of Central Brazil and Bolivia, may have originated recently, between four to eight million years ago, following the emergence of inflammable C4 grasses as a dominant element in this ecosystem. To test this hypothesis, we generated time-calibrated molecular phylogenies for Mimosa (Leguminosae) and tribe Microlicieae (Melastomataceae; using previously published data), which are both remarkably rich in fire-adapted narrow endemic Cerrado species, as well as densely sampled phylogenies for the legume genera Andira and Lupinus, which contain small numbers of fire-adapted Cerrado species. For Mimosa, results show that Cerrado endemics originated independently in multiple disparate lineages within the genus. However, the majority of Cerrado endemics (75% of the Cerrado Mimosas) fall into two large clades rich in fire-adapted species. It is notable that these two independent Cerrado Mimosa radiations started diversifying simultaneously, around 3.5 million years ago (Myr). The Cerrado endemics in the Microlicieae are placed in a single well supported clade with an estimated age of 9.8 Myr. Ages for the Andira and Lupinus Cerrado lineages are estimated to be younger than 3 Myr. Our results support the hypothesis of a recent origin of the Cerrado that involved rapid and successful adaptive radiation of an endemic-rich fire-tolerant flora, and suggest that Cerrado lineages are nested within clades located in diverse wet, dry and subtropical grassland biomes.
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1 - University of Oxford, Department of Plant Sciences, South Parks Road, Oxford, OX1 3RB, United Kingdom
2 - Universidad Autónoma Metropolitana - Iztapalapa, Departamento de Biología, Apdo. Postal 55-535, México, D.F., 09340, México
3 - Universidade Estadual de Feira de Santana, Departamento de Ciências Biológicas, Km 03, BR 116, Campus, Feira de Santana, Bahia, 44031–460, Brazil
4 - Cornell University, L.H. Bailey Hortorium, Department of Plant Biology, 412 Mann Library, Ithaca, NY, 14853, USA
5 - Royal Botanic Garden Edinburgh, 20A Inverleith Row, Edinburgh, EH3 5LR, United Kingdom
6 - University of Oxford, Department of Plant Sciences, South Parks Road, Oxford, Oxfordshire, OX1 3RB, United Kingdom
origins of biomes.
Presentation Type: Oral Paper:Papers for Sections
Date: Wednesday, July 30th, 2008
Time: 2:00 PM