Leslie, Andrew , Beaulieu, Jeremy , Rai, Hardeep , Crane, Peter , Donoghue, Michael , Mathews, Sarah .
Hemisphere-scale Differences in Conifer Evolutionary Dynamics.
Northern and Southern Hemispheres differ fundamentally with respect to the distribution of seas and landmasses, and in the dynamism of their landscapes and climate histories over the past 65 million years. Conifers present an excellent opportunity to explore how such broad geographic and climatic differences may influence evolutionary dynamics within and between groups of organisms, since most living species belong to lineages that have been broadly confined to the Northern or Southern Hemisphere through the Cenozoic. Based on a critical review of the conifer fossil record, we developed an age-calibrated phylogeny that samples more than 80% of living conifer species for four chloroplast and nuclear genes. Our results show that most extant conifer species diverged recently during the Neogene within larger clades that were generally established during the later Mesozoic. However, clades that diversified mainly in the Southern Hemisphere contain a greater number of old lineages than their counterparts in the Northern Hemisphere, and have a median node age more than twice that of corresponding Northern lineages. In contrast, most Northern Hemisphere conifer diversity is found in several diverse genera with recent species divergences. We further explored the evolutionary dynamics of these groups using several coalescence-based diversification models, which suggest Northern Hemisphere conifer lineages have higher rates of species turnover compared to their counterparts in the Southern Hemisphere. These contrasts in median node age and species turnover rates suggest that higher rates of landscape-scale disturbance in the north, together with greater climate and landscape stability in the south, were important in determining broad patterns of conifer evolution.
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1 - Yale University, School of Forestry and Environmental Studies, 195 Prospect Street, New Haven, CT, 06511, USA
2 - Yale University, Ecology and Evolutionary Biology, P.O. Box 208106, New Haven, CT, 06520, USA
3 - Yale University, Department Of Ecology And Evolutionary Biology, YALE UNIV-PO BOX 208105, New Haven, CT, 06520-8105, USA
4 - Harvard University, Harvard University Herbaria, 22 Divinity Avenue, Cambridge, MA, 02138, USA
Presentation Type: Oral Paper:Papers for Topics
Location: Franklin B/Hyatt
Date: Tuesday, July 10th, 2012
Time: 1:30 PM