Relaxed phylogenies and dating with confidence

08 Apr

We find no significant rate autocorrelation among branches in three large datasets, suggesting that autocorrelated models are not necessarily suitable for these data.In addition, we place these datasets on the continuum of clocklikeness between a strict molecular clock and the alternative unrooted extreme.In phylogenetics, the unrooted model of phylogeny and the strict molecular clock model are two extremes of a continuum.

The molecular clock was first tested in 1962 on the haemoglobin protein variants of various animals, and is commonly used in molecular evolution to estimate times of speciation or radiation.If this is correct, the cytochrome c of all mammals should be equally different from the cytochrome c of all birds.Since fish diverges from the main stem of vertebrate evolution earlier than either birds or mammals, the cytochrome c of both mammals and birds should be equally different from the cytochrome c of fish.It is sometimes called a gene clock or an evolutionary clock.The notion of the existence of a so-called "molecular clock" was first attributed to Émile Zuckerkandl and Linus Pauling who, in 1962, noticed that the number of amino acid differences in hemoglobin between different lineages changes roughly linearly with time, as estimated from fossil evidence.