With a Little Help From My Friends: Hyperparasitism Allows a Generalist Mistletoe to Expand Habitat Use

Abstract

Mistletoes largely vary in the number of species that they can parasitize. In the temperate rainforests of southern Chile, we found two mistletoe species: Tristerix corymbosus, a generalist species able to parasitize at least 30 plant species, and Desmaria mutabilis, which only parasitizes Nothofagus trees (that T. corymbosus is unable to parasitize). Nevertheless, we found some Nothofagus trees parasitized by T. corymbosus. How is this happening? We found that T. corymbosus parasitize D. mutabilis individuals, which are parasitizing Nothofagus trees. Such hyperparasitic relationship allows T. corymbosus to be present in Nothofagus-dominated forests, which otherwise will not be possible. Photo 1. Tristerix corymbosus flowering during the austral winter in the Nahuelbuta National Park, southern Chile. This mistletoe species flowers between March and October, being the main nectar source for hummingbirds during this period. Photo credit: Francisco E. Fontúrbel. Photo 2. Desmaria mutabilis flowering during the austral summer (January) in Nahuelbuta National Park. While its flowering period is relatively short (about 1 month), D. mutabilis flowers are intensely visited by pollinators, including hummingbirds and several kinds of insects. Photo credit: Francisco E. Fontúrbel. Photo 3. Desmaria mutabilis parasitizing a Nothofagus pumilio tree. The picture shows late flowers and some unripe fruits. Photo credit: Francisco E. Fontúrbel. Photo 4. Several Desmaria mutabilis mistletoes in an old-growth Nothofagus spp. forest stand at the Nahuelbuta National Park. Photo credit: Francisco E. Fontúrbel. Photo 5. A Tristerix corymbosus mistletoe parasitizing a Desmaria mutabilis individual, which is parasitizing a Nothofagus pumilio tree. Photo credit: Francisco E. Fontúrbel. These photographs illustrate the article “With a little help from my friends: Hyperparasitism allows a generalist mistletoe to expand habitat use” by Fontúrbel et al. published in Ecology. https://doi.org/10.1002/ecy.3919