New uses for new phylogenies

Comparison of the molecular structure of genetic material from living species reveals evolutionary relationships, and estimates of dates when pairs of species last shared a common ancestor. The resulting evolutionary trees, which are accumulating rapidly in the literature to complement those trees produced from fossil records, can be used to reveal hitherto unsuspected patterns in the evolutionary record. In particular, the trees can be analysed to show when rates of speciation and extinction were abnormally high or low. Together with estimates of ancestral character states and environments, these data throw new light on the reasons for speciation and extinction. This article describes how statistical methods are being developed and used to analyse molecular phylogenies.