This week at Nothing in Biology Makes Sense! Noah Reid takes a look at a study that attempts to disentangle the effects of reproductive isolation between species and the rate at which new species are formed. Why would you want to do that? So you can tell whether the former causes the latter!
RI [reproductive isolation] is often thought to be important in diversification because some theory predicts that even low levels of intermating between populations can prevent divergence from occurring and because hybridization between divergent populations can cause them to homogenize, or cause one population to become extinct. If these factors commonly prevent speciation or cause incipient species to go extinct, one might expect a positive correlation between the rate of evolution of RI and DR [species diversification]. This paper is the first test of this prediction.
But, of course, a lot of biologists would say that the evolution of reproductive isolation is the evolution of a new species … so things get a bit complicated. Go read the whole thing, and see what you think.◼