Marine dating network updating the root hint
Recently, calibrations made with ancient DNA (a DNA) from younger dates have yielded faster rates, suggesting that estimates of the molecular rate of change depend on the time of calibration, decaying from the instantaneous mutation rate to the phylogenetic substitution rate.
a DNA methods for recent calibrations are not available for most marine taxa so instead we use radiometric dates for sea-level rise onto the Sunda Shelf following the Last Glacial Maximum (starting ∼18,000 years ago), which led to massive population expansions for marine species.
Mean rates estimated with this method for mitochondrial coding genes in three invertebrate species are elevated in comparison to older calibration points (2.3–6.6% per lineage per million years), lending additional support to the hypothesis of calibration time dependency for molecular rates.
The observation that genetic distances between taxa are correlated with the amount of time since they diverged first gave rise to the idea that DNA may evolve at a relatively constant rate: the molecular clock (Zuckerkandl and Pauling 1965).
Only species which pass both tests can be considered suitable for further studies to obtain reliable age information.
This amino acid geochronological technique is also applied to midden deposits at two latitudinal extremes: Northern Scotland and the Southern Red Sea.
2002; Smith and Peterson 2002; Bromham and Penny 2003; Takahata 2007).
Instead of divergence dating, we use a two-epoch coalescent model of logistic population growth preceded by a constant population size to infer a time in mutational units for the beginning of these expansion events.