The hypothesis that in groups of permanent parasites the classification of the parasites corresponds directly with the natural relationships of their hosts. For example, closely related species of mammals are generally parasitized by closely related species of lice. The rule is based on the assumption that the intimate associations of parasites with their hosts necessitate that they evolve and speciate in harmony with their hosts. As a result of this coevolution, speciation and patterns of divergence in host taxa are paralleled by their parasites. An underlying assumption of the Fahrenholz rule is that there is no dispersal of parasites between unrelated hosts. The eponym honors the German entomologist, Heinrich Fahrenholz, who formulated the concept. See resource tracking.
Subjects: Genetics and Genomics.