Tuesday, December 11, 2012

Northern Hemisphere Conifers Are Evolving Faster

Hemisphere-scale differences in conifer evolutionary dynamics


1. Andrew B. Leslie (a,*)
2. Jeremy M. Beaulieu (b)
3. Hardeep S. Rai (c)
4. Peter R. Crane (a)
5. Michael J. Donoghue (b,*)
6. Sarah Mathews (d)


a. School of Forestry and Environmental Studies, Yale University, New Haven, CT 06511;

b. Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT 06520;

c. Wildland Resources Department, Utah State University, Logan, UT 84322; and

d. Arnold Arboretum of Harvard University, Boston, MA 02131

*. To whom correspondence may be addressed. E-mail: andrew.leslie@yale.edu or michael.donoghue@yale.edu.


Fundamental differences in the distribution of oceans and landmasses in the Northern and Southern Hemispheres potentially impact patterns of biological diversity in the two areas. The evolutionary history of conifers provides an opportunity to explore these dynamics, because the majority of extant conifer species belong to lineages that have been broadly confined to the Northern or Southern Hemisphere during the Cenozoic. Incorporating genetic information with a critical review of fossil evidence, we developed an age-calibrated phylogeny sampling ∼80% of living conifer species. Most extant conifer species diverged recently during the Neogene within clades that generally were established during the later Mesozoic, but lineages that diversified mainly in the Southern Hemisphere show a significantly older distribution of divergence ages than their counterparts in the Northern Hemisphere. Our tree topology and divergence times also are best fit by diversification models in which Northern Hemisphere conifer lineages have higher rates of species turnover than Southern Hemisphere lineages. The abundance of recent divergences in northern clades may reflect complex patterns of migration and range shifts during climatic cycles over the later Neogene leading to elevated rates of speciation and extinction, whereas the scattered persistence of mild, wetter habitats in the Southern Hemisphere may have favored the survival of older lineages.

A pop sci write up of the same.

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