A hypothesis involving host-parasite coevolution according to which ectoparasites track a particular resource, such as a type of skin, hair, or feathers. If in addition there is opportunity for a given species of parasite to disperse to unrelated host species, then there will be no direct parallel relationship between the taxonomy of the hosts and that of their parasites (contrast with Fahrenholz rule). In birds, for example, the same species of mite may be found on birds from different orders, and a single species of bird may be parasitized by different lice species. Thus, birds and their parasites show little phylogenetic parallelism.
Subjects: Genetics and Genomics.