No link between population isolation and speciation rate in squamate reptiles

Speciation rate measures how quickly a species gives rise to new species, and this rate varies up to 50-fold across vertebrate groups. In this study, we explore one hypothesis that explains this variation: species that form geographically isolated populations more readily should also form new species more readily and thus should have higher speciation rates. This hypothesis links microevolutionary studies of speciation with macroevolutionary studies of biodiversity. We test this hypothesis using a diverse set of lizard and snake species found in the South America savannahs. We find no effect of geographic population isolation on speciation rates. Our results suggest that other stages in the speciation process are more important controls on speciation rate variation.