Dating dispersal and radiation in the gymnosperm gnetum
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.
Perhaps because of the extinction of entire clades, molecular-clock studies of gymnosperms consistently have inferred young, usually Oligocene, ages for the crown groups of living genera, e.g., –31).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.Support values for major groups are high, with three-quarters of the genus-level nodes having Bayesian coestimation of topology and divergence time (BEAST, using uniform prior distributions on calibration ages) (43) generally gave the oldest ages, and Penalized likelihood (44, 45) gave the youngest (Table S3).An alternative Bayesian approach, which used a fixed topology (MULTIDIVTIME) (46), yielded ages for short-branched nodes (most nodes within Cupressoideae; Fig.
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.