Cospeciation

Host-parasite phylogenies can be altered by host switching, extinction, independent speciation, and other ecological events, making cospeciation harder to detect.

[4] In 1913, Heinrich Fahrenholz proposed that the phylogenies of both the host and parasite will eventually become congruent, or mirror each other when cospeciation occurs.

Thus, to determine if cospeciation has occurred within a host-parasite relationship, scientists have used comparative analyses on the host and parasite phylogenies.

Studying cospeciation within plant-insect relationships, he proposed that species have a physiological range of conditions and environments.

"Ecological fitting", as it is known, means more closely related parasites will share similar traits that pertain to surviving on a particular host.

[5][6] Fahrenholz's rule appears to be observed in the parasitic cospeciation of pocket gophers and chewing lice.

[9] Among animals, symbiotic cospeciation is seen between Uroleucon (aphids) and Buchnera (plants in the Orobanchaceae),[10] between deep sea clams and chemoautotrophic bacteria,[11] and between Dendroctonus bark beetles and certain fungi.

Coupled with extinction or independent speciation, phylogenetic comparisons can become complicated and entirely mask the cospeciation event.