State Key Laboratory of Grassland Agro-Ecosystem, School of Life Sciences, Lanzhou University, Lanzhou, Gansu 730000, People's Republic of China.
Proc Natl Acad Sci U S A. 2012 May 15;109(20):7793-8. doi: 10.1073/pnas.1114319109. Epub 2012 May 1.
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.
大多数现存的裸子植物属级辐射是始新世或更年轻的,反映了始新世/渐新世边界[约 2300 万年前(Ma)]气候冷却期间的广泛灭绝。最近的生物地理学研究表明,裸子植物和被子植物都有许多远距离扩散的例子。灭绝和远距离扩散共同作用可能会抹去历史生物地理学信号。尽管存在这个问题,我们还是表明,裸子植物柏科(162 种,32 属)的系统发育关系表现出了从侏罗纪/白垩纪泛古陆分裂中预期的模式。我们为 122 个代表所有属的物种生成了一个系统发育树,每个物种使用多达 10000 个核苷酸的质体、线粒体和核序列。依靠 16 个化石校准点和三种分子定年方法,我们表明柏科起源于三叠纪,当时泛古陆是完整的。两个亚科,即北美的 Cupressoideae 和冈瓦纳的 Callitroideae,在 153 Ma 左右发生了分歧(124-183 Ma),当时冈瓦纳和劳拉西亚正在分离。另外三个涉及北半球和南半球的洲际分离与泛古陆的分裂同时发生或紧随其后。