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Edited by Charles C. Davis, Harvard University, Cambridge, MA, and accepted by the Editorial Board March 21, 2012 (received for review September 2, 2011)
Abstract
Most extant genus-level radiations in gymnosperms are of Oligocene age or younger, reflecting widespread extinction during climate cooling at the Oligocene/Miocene boundary [∼23 million years ago (Ma)]. Recent biogeographic studies have revealed many instances of long-distance dispersal in gymnosperms as well as in angiosperms. Acting together, extinction and long-distance dispersal are likely to erase historical biogeographic signals. Notwithstanding this problem, we show that phylogenetic relationships in the gymnosperm family Cupressaceae (162 species, 32 genera) exhibit patterns expected from the Jurassic/Cretaceous breakup of Pangea. A phylogeny was generated for 122 representatives covering all genera, using up to 10,000 nucleotides of plastid, mitochondrial, and nuclear sequence per species. Relying on 16 fossil calibration points and three molecular dating methods, we show that Cupressaceae originated during the Triassic, when Pangea was intact. Vicariance between the two subfamilies, the Laurasian Cupressoideae and the Gondwanan Callitroideae, occurred around 153 Ma (124–183 Ma), when Gondwana and Laurasia were separating. Three further intercontinental disjunctions involving the Northern and Southern Hemisphere are coincidental with or immediately followed the breakup of Pangea.
Footnotes
↵1K.M. and R.I.M. contributed equally to this work.
- ↵2To whom correspondence should be addressed. E-mail: liujq{at}nwipb.ac.cn.
Author contributions: J.L., K.M., and R.I.M. designed research; K.M., R.I.M., L.Z., Y.P., P.T., R.R.M., and J.L. performed research; S.S.R. contributed new reagents/analytic tools; K.M., J.L., and S.S.R. analyzed data; and K.M., J.L., S.S.R., and R.I.M. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission. C.C.D. is a guest editor invited by the Editorial Board.
Data deposition: The sequences reported in this paper have been deposited in the GenBank database (JF725702–JF725991). GenBank accession numbers and provenance of sequenced samples are provided in Table S1.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1114319109/-/DCSupplemental.
Freely available online through the PNAS open access option.
Biogeographic history of Cupressaceae
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