ABSTRACT
The topologies or branching sequences of many molecular phylogenies are of special interest. The clades indicate standard, repeated distribution patterns and precise, interlocking biogeographic structure. In contrast, molecular clock dates are often unreliable, because of problems with calibration, assignment of priors in Bayesian analyses, models of rate changes, and other constraints. Molecular clock estimates of clade ages are sometimes regarded as “trustworthy” (Ree and Sanmartín, 2009), but the dating is probably the weakest part of the molecular enterprise. A detailed treatment of angiosperms cited molecular clock dates for many clades, but warned that these “should all be treated with extreme caution” (Stevens, 2014). Later, Stevens (2016) referred again to the clade dates and wrote: “most must be seriously inaccurate.”
