Testing the Context and Extent of Host-Parasite Coevolution

Testing the context and extent of host-parasite coevolution. Syst. Zool. 28:299– 307.—Coevolution is defined as a combination of two processes: co-accommodation between host and parasite with no implication of host or parasite speciation and co-speciation, indicating concomitant host and parasite speciation. Parasite speciation in general is viewed as primarily the result of allopatric speciation processes regardless of host speciation or changes in host type. The observation that co-speciation of hosts and parasites forms a predominant pattern relates to a more general principle of biotic allopatric speciation explicit in the vicariance biogeography model, more than to an assumption that host speciation somehow causes parasite speciation. The close ecological relationship between hosts and parasites, which may be depicted using a variation of the MacArthur-Wilson island biogeography model, explains their spatial proximity at any time during which an isolating event occurs and thus may be necessary in some cases, but is not sufficient to explain parasite speciation, coevolution, or parasite phylogeny.