Data from: Morphological datasets fit a common mechanism much more poorly than DNA sequences and call into question the Mkv model

The Mkv evolutionary model, based on minor modifications to models of
molecular evolution, is being increasingly used to infer phylogenies from
discrete morphological data, often producing different results from
parsimony. The critical difference between Mkv and parsimony is the
assumption of a “common mechanism” in the Mkv model, with branch lengths
determining that probability of change for all characters increases or
decreases at the same tree branches by the same exponential factor. We
evaluate whether the assumption of a common mechanism applies to
morphology, by testing the implicit prediction that branch lengths
calculated from different subsets of characters will be significantly
correlated. Our analysis shows that DNA (38 datasets tested) is often
compatible with a common mechanism, but morphology (86 datasets tested)
generally is not, showing very disparate branch lengths for different
character partitions. The low levels of branch length correlation
demonstrated for morphology (fitting models without a common mechanism)
suggest that the Mkv model is too unrealistic and inadequate for the
analysis of most morphological datasets.