The showy mistletoes (family Loranthaceae) are mostly aerial stem parasites that belong to the sandalwood order. The family originated in Gondwana and is most diverse in the Tropics and the Southern Hemisphere. All Loranthaceae are obligate hemiparasites, unable to survive without connecting to the vascular system of their host. The degree of host specificity in mistletoe-host interactions is thus a fundamental determinant of mistletoe diversity, persistence, geographic distribution, and abundance. Additionally, their floral displays and fleshy fruits link them with their animal pollinators and avian dispersers. Mistletoe patches in host canopies increase complexity in canopy structure and are a focal point in distinctive plant-animal interaction networks. We are building a phylogenetic framework to study the evolution, biogeography, and ecological interactions of Australasian showy mistletoes.