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The significant reduction of variance in divergence time estimates upon extending cross-bracing to uncalibrated nodes makes this approach greatly suited for evolutionary inference in groups with poor fossil records, with particular reference to terrestrial arthropods. Grounded upon the tenet that the amount of time elapsed since the last common ancestor of two homologous sequences is statistically proportional to the number of differences between sequences, molecular dating has become an invaluable tool for hypothesis testing in evolutionary biology .
In contrast to simple early approaches that relied upon assumptions of a global strict molecular clock or a series of local clocks, current methods in molecular dating deploy an array of sophisticated models and algorithms for inferring evolutionary rates over phylogenetic trees, including relaxed assumptions for rate variation across molecular phylogenies, use of fossil taxa as terminals in a phylogeny, and analysis of historical molecular sequence data .
A new statistical method for estimating divergence dates of species from DNA sequence data by a molecular clock approach is developed.
This method takes into account effectively the information contained in a set of DNA sequence data.
Kumar S, Filipski A, Swarna V, Walker A, & Hedges SB. Placing confidence limits on the molecular age of the human-chimpanzee divergence. Assessing the quality of molecular divergence time estimates by fossil calibrations and fossil-based model selection. Comparison of likelihood and Bayesian methods for estimating divergence times using multiple loci and calibration points, with application to a radiation of cute-looking mouse lemur species.
Proceedings of the National Academy of Sciences 1842-18847. Philosophical Transactions of the Royal Society of London B 377-1483.
By examining the evolution of 16S r RNA gene in obligate endosymbionts, which can be calibrated by the fossil record of their hosts, we found that the rates are consistent within a clade but varied widely across different bacterial lineages.
Genome-wide estimates of nonsynonymous and synonymous substitutions suggest that these two measures are highly variable in their rates across bacterial taxa.
We applied such a refinement to molecular dating in chelicerates, one of the earliest groups of arthropods present in the fossil record, but whose molecular dating has been greatly inconsistent in the literature.
We inferred divergence times using hemocyanin paralogs isolated from We show that extending cross-bracing to uncalibrated nodes greatly reduced variance in estimates of divergence times throughout the phylogeny, particularly for estimated diversification ages of spiders and scorpions, whereas cross-bracing calibrated nodes alone did not affect age estimation for uncalibrated, derived clades.
Our results document a wide range of substitution rates across genes and bacterial taxa.Tags: Adult Dating, affair dating, sex dating