Table 5.

Examples of parasite groups exhibiting hosts switches likely to have played a major role in diversification of that group.

With respect to Plasmodium and related genera of blood parasites, major clades are associated with shifts into different families of dipteran vectors, and the Plasmodium species of birds and squamate reptiles show evidence of repeated switching back and forth (Martinsen et al., 2008).

Major lineages within the blood fluke genus Schistosoma are defined by acquisition of different genera of even families of snail intermediate hosts, by host switching (Morgan et al., 2003). Long-range host shifts involving acquisition of both new snail and vertebrate hosts appear to have occurred during the history of schistosomes (Brant and Loker, 2005).

Zietara and Lumme (2002) note that as many as 20,000 species of the monogenean genus Gyrodactylus may exist, and note that in a study of one subgenus (Limnonephrotus) that several host switch events were statistically confirmed, including into new host families, supporting the idea that host switching is a means to drive innovation and adaptive radiation in these ectoparasites.

It appears that host switching has been common in trypanorhynch tapeworms, one of the most diverse and abundant groups of metazoan parasites of elasmobranchs (Olson et al., 2010)

Coronaviruses have likely undergone several host switches, between mouse and rat, chicken and turkey, birds and mammals, and between humans and other mammals (Rest and Mindell, 2003).

Braconid wasps of the subfamily Euphorinae have undergone extensive host switching among phylogenetically distantly related insect host groups, often followed by adaptive radiations of the parasitoids within a particular host lineage (Shaw, 1988).

“Infection of a novel host is the most frequent cause of fungal emerging disease” (Stukenbrock and McDonald, 2008; Giraud et al., 2010)