Relaxed phylogenies and dating with confidence examples of profiles for dating sites
The resulting dates have subsequently been used as a temporal framework for many ecological studies (e.g., Slingsby and Verboom, 2006; Vamosi et al., 2006; Edwards et al., 2007; Webb et al., 2008), as well as “external,” or secondary, calibration points for subsequent divergence time analyses of groups that may lack reliable fossils (e.g., Park et al., 2006). (2001) used nonparametric rate smoothing (NPRS) (Sanderson, 1997) to estimate divergence times across angiosperms using (Sims et al., 1998), both from the Late Santonian.With this approach, they estimated an age for angiosperms of 179–158 Ma.: It has been 8 years since the last comprehensive analysis of divergence times across the angiosperms.Given recent methodological improvements in estimating divergence times, refined understanding of relationships among major angiosperm lineages, and the immense interest in using large angiosperm phylogenies to investigate questions in ecology and comparative biology, new estimates of the ages of the major clades are badly needed.We also provide dates for all major angiosperm clades (including 45 orders and 335 families [208 stem group age only, 127 both stem and crown group ages], sensu APG III).Our analyses provide a new comprehensive source of reference dates for major angiosperm clades that we hope will be of broad utility.• : Based on the analysis for which we set fossils to fit lognormal priors, we obtained an estimated age of the angiosperms of 167–199 Ma and the following age estimates for major angiosperm clades: Mesangiospermae (139–156 Ma); Gunneridae (109–139 Ma); Rosidae (108–121 Ma); Asteridae (101–119 Ma).• : With the exception of the age of the angiosperms themselves, these age estimates are generally younger than other recent molecular estimates and very close to dates inferred from the fossil record.
This lineage-specific rate heterogeneity should be accounted for, when possible, in divergence time estimation.Improved estimations of divergence times will concomitantly improve our understanding of both the evolutionary history of the angiosperms and the patterns and processes that have led to this highly diverse clade.