Tristerix is a genus of hemiparasitic mistletoes in the family Loranthaceae (order Santalales), native to the Andes mountain range of South America. The genus ranges from Colombia and Ecuador in the north to Chile and Argentina in the south, where its roughly 11 species grow as aerial stem parasites on a variety of host shrubs and trees.
Members of Tristerix are woody perennials that attach to host branches via haustoria, extracting water and nutrients while typically retaining their own photosynthetic leaves — the exception being Tristerix aphyllus, a nearly leafless species that parasitises cacti. The genus is distinguished within the New World Loranthaceae by its simple, terminal, racemose inflorescences bearing 4- or 5-merous flowers with versatile anthers and endosperm, as well as by fused cotyledons and the absence of the epicortical roots found in related genera.
Flowers are typically tubular and brightly coloured, adapted for pollination by hummingbirds and flowerpiercers. Seed dispersal is carried out predominantly by birds, though the marsupial Dromiciops gliroides (monito del monte) also acts as a disperser in southern South America — a relationship of particular evolutionary interest given the ancient biogeographic links between South American and Australasian Loranthaceae.
Distribution
Tristerix is endemic to the Andes of South America, with species recorded from Colombia and Ecuador in the north through Peru and Bolivia to Chile and Argentina in the south. The genus reaches its greatest diversity in the temperate southern Andes.
Ecology
Species of Tristerix are aerial stem parasites that penetrate host-plant vascular tissue via haustoria. Their tubular, often red or orange flowers are strongly associated with hummingbird and flowerpiercer pollination syndromes. Seeds are dispersed chiefly by fruit-eating birds; the marsupial Dromiciops gliroides is a notable mammalian disperser in Chilean and Argentine forests, and its relationship with T. corymbosus has been described as a coevolved mutualism.
Taxonomy Notes
Tristerix belongs to the family Loranthaceae (order Santalales), the larger of the two families of flowering-plant parasites commonly called mistletoes. Within Loranthaceae it is placed among the New World genera and is distinguished from close relatives by its racemose inflorescences, 4–5-merous flowers with versatile anthers, endosperm, fused cotyledons, and the absence of epicortical roots.
