The build-up of species locally within a region by allopatric speciation depends on
geographically separated (allopatric) sister populations becoming reproductively
incompatible followed by secondary sympatry. Among birds, this has happened frequently in
remote archipelagos, spectacular cases including the Darwin's finches (Geospizinae) and
Hawaiian honeycreepers (Drepanidinae), but similar examples are lacking in archipelagos
nearer to continental landmasses. Of the required steps in the speciation cycle, achievement …