Species-level phylogenies derived from molecular data provide an indirect record of the
speciation events that have led to extant species. This offers enormous potential for
investigating the general causes and rates of speciation within clades. To make the most
of this potential, we should ideally sample all the species in a higher group, such as a
genus, ensure that those species reflect evolutionary entities within the group, and rule
out the effects of other processes, such as extinction, as explanations for observed
patterns. We discuss recent practical and theoretical advances in this area and outline how
future work should benefit from incorporating data from genealogical and phylogeographical scales.