Dating dispersal and radiation in the gymnosperm gnetum
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.
Recent biogeographic studies have revealed many instances of long-distance dispersal in gymnosperms as well as in angiosperms.
Cupressaceae occur on all continents except Antarctica and comprise 162 species in 32 genera (see Table S2 for subfamilies, genera, and species numbers).
The family has a well-studied fossil record going back to the Jurassic (32–36).
Experiments have confirmed the theoretical expectation that such sampling leads to the erroneous inference of diversification rate downturns (41, 42).
We aimed to test the hypothesis that, given their fossil record, the deepest Cupressaceae divergences should reflect the break-up of Pangea and that evolution of the family then continued on the separating continental landmasses.