Genetic and morphological disparity are decoupled

The last three decades have seen an expansion of morphological disparity analyses, which is now routinely indexed alongside species diversity in clades. Strikingly, species diversity is often a poor correlate of morphological diversity across clades and time bins. Small clades with only a handful of species can encompass spectacular morphological diversity, whereas species rich groups may be morphologically highly conservative and vice versa. Higher morphological disparity should ultimately result from changes at the DNA level, and we might expect it to be associated with greater divergence between species at the molecular level. However, genetic or molecular disparity has never been quantified explicitly in a manner analogous to morphological disparity, and its possible relationship with both morphological disparity and species diversity has never been assessed. To investigate this relationship mammals represent an ideal study group, since their diversity is strongly heterogeneous acro...