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Abstract Detail


Biogeography

Lo, Eugenia [1], Donoghue, Michael J. [2].

Shifts in the diversification rate within the Rosaceae supertribe Pyrodae and the associated biogeographic and character changes during the Eocene.

The Pyrodae represents a group of woody species that have undergone a complex history of hybridization and polyploidization. Species are widespread in the Northern Hemisphere and are thought to have originated as early as the Paleocene based on an abundant fossil record for the group. Despite previous efforts in elucidating relationships among genera, divergence time and evolutionary history of species remain unclear at broad evolutionary scales. In order to obtain a robust phylogeny for such inferences, sequences of 11 chloroplast genes (a total of 11,712bp) and ITS region were obtained for 410 species representing 26 described genera. Maximum likelihood and parsimony analyses indicated two significantly conflicting positions in Pseudocydonia and the clade Micromeles between the chloroplast and ITS phylogenies. Such conflicts suggest the hybrid origins of their ancestral lineages. We detected six significant shifts in the rate of diversification in our phylogeny. The first significant shift occurred between the lineage Vauquelinia and the Pyrinae genera, which we estimate to have occurred around 53±3 Mya. This may be best explained as a dispersal event from a relatively restricted range in Central and South America into the northern temperate and circumboreal regions of the Old and New World, and is temporally consistent with the global climatic warming and vegetational changes during the Paleocene-Eocene transition. We also estimate the origin of the three major Pyrodae clades namely the {Amelanchier-Crataegus}, {Aria-Malus}, and {Cotoneaster-Sorbus} clades to have occurred around 45±4 Mya, with each clade containing at least one shift in diversification rate. In each case, these shifts may relate to changes in ploidy level, woodiness, or distributional range of species. However, given that these shifts were estimated to have occurred between 25-35 Mya, we infer that the gradual cooling and increased aridity in the Oligocene could have resulted in the extinction of some species, particularly those that were unable to adapt to the changing environments and/or switch to alternative ecological niches.

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1 - Yale University, Ecology & Evolutionary Biology, PO Box 208106, New Haven, CT, 06520
2 - Yale University, Ecology and Evolutionary Biology, P.O. Box 208105, New Haven, CT, 06520, USA

Keywords:
Diversification rate
polyploidy
extinction
Rosaceae
hybridization.

Presentation Type: Oral Paper:Papers for Topics
Session: 3
Location: 551A/Convention Center
Date: Monday, August 2nd, 2010
Time: 11:15 AM
Number: 3013
Abstract ID:533


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