Cospeciation

Cospeciation is a form of coevolution in which the speciation of one species drives speciation in another, most often studied in host-parasite relationships though it also occurs in symbiotic partnerships. When a host species splits into new species, its parasites become geographically or reproductively separated along with it, and this loss of contact between parasite populations can itself drive the parasite to speciate. A principle known as Fahrenholz's rule holds that where true cospeciation occurs, the evolutionary trees of host and parasite come to mirror one another, though confirming genuine cospeciation is difficult because host switching, extinction and independent speciation can all produce a similar-looking but false pattern. Parasitic cospeciation has been documented in pocket gophers and their chewing lice, and symbiotic cospeciation appears between fig trees and fig wasps, between deep sea clams and the chemoautotrophic bacteria they host, and in the gut microbes of primates.