What increases the rate of speciation?

The biggest factor speeding up speciation is geographic isolation of populations. When a single species is divided into two or more groups so that the members of one group cannot breed with another, this allows each group to evolve independently and eventually become distinct species.

While geographic isolation is thought to be behind most speciation, there are circumstances when new species arise from a population without any long distances or other physical divisions between members. In this case, it is thought that one part of the population changes habits, such as a parasite beginning to attack a new host, and this division in behavior leads to speciation.