Dating dispersal and radiation in the gymnosperm gnetum
Confidence intervals around estimates from the two Bayesian approaches overlapped (Table S3).
With all three dating approaches, the more densely sampled 144-taxon dataset produced slightly older age estimates (compare Fig.
Possible changes in diversification rates were inferred with an approach that accounts for nonrandom taxon sampling in molecular phylogenies (40).
Nonrandom sampling arises when phylogenies include at least one species per genus but not all congenerics, thereby overrepresenting deep nodes (diversification events) in the tree.
The fossil record shows that gymnosperms dominated the vegetation of Pangea but declined in dominance and abundance from the Mid-Cretaceous onwards (11, 12).
An alternative Bayesian approach, which used a fixed topology (MULTIDIVTIME) (46), yielded ages for short-branched nodes (most nodes within Cupressoideae; Fig.Yellow lines represent species occurring in Africa south of the Sahara. Gray bars represent 95% HPD intervals for nodes 1–10.Gray (run 1) and purple (run 7) normal distributions represent the posterior for the BEAST age estimate of node 7 when uniform or lognormal priors were applied to calibration points.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.–3).
Search for dating dispersal and radiation in the gymnosperm gnetum:
Around 160–138 million years ago (Ma) (1, 3), Pangea broke up into two supercontinents: Laurasia, comprising land that eventually gave rise to North America, Europe, and much of Asia, and Gondwana, made up of land that subsequently gave rise to South America, Africa, India, Antarctica, and Australia.