Mistletoes - cryptic mimicry

Host specificity

One necessary condition for the origin of cryptic mimicry in the parasite is high host specificity, in which the mistletoe has a narrow range of host species, and appears to be unlikely or unable to grow on other species. As the mistletoe becomes more and more specialized for growth on its preferred host, it becomes less and less adapted for growth on other, different hosts. In Australian open forest and woodland communities there are usually few dominant tree species, generally one or a few species of Eucalyptus, Acacia, Melaleuca, Casuarina, etc., and many mistletoes have evolved high host specificity for efficient colonization of the dominant trees in the community. Clearly without high host specificity there could be no mimicry. A subjective assessment of host-parasite resemblance suggests that of the 46 species of aerial stem-parasitic loranths in open forest and woodland habitats in Australia, 36 species (78%) are either highly host-specific, with a close resemblance to the host, or have a close resemblance to a very common host over a large part of the species range.

Host genera recorded on herbarium specimen sheets for each species of mistletoe are listed in the Checklist.