THE CYTOGEOGRAPHY AND RELATIONSHIPS OF THE VISCACEOUS AND EREMOLEPIDACEOUS MISTLETOES

Abstract

SummaryKnown chromosome numbers in the Viscaceae and Eremolepidaceae are reviewed and 73 new records added. No basic number is presently evident for either family as a whole. In the Vicaceae two fundamental chromosome groups are apparent. The first is characterized by x = 14 and is itself composed of two subgroups, one with large chromosomes (Dendrophthora‐Phoradendron), and the other with medium sized chromosomes (Arceuthobium‐Korthalsella). The second chromosome group is composed of Viscum and its close relatives which possess numbers of x = 10, 11, 12, and 13 and which have large chromosomes.In the x = 14 group, the Dendrophthora‐Phoradendron alliance is strictly New World. The Arceuthobium‐Korthalsella alliance, however, has both Old and New World representation. Arceuthobium is present in both the Old and New Worlds and Korthalsella has an Old World and Pacific distribution. The Viscum alliance is strictly Old World.Some infra‐generic aneuploidy is known in Viscum and Dendrophthora. Polyploidy is apparently rare, known only in Phoradendron from the Galápagos Islands and in Viscum from New Guinea and northern Australia.A northern origin is postulated for the Viscaceae, with subsequent widespread radiation into the tropics of both the New and Old Worlds.The Eremolepidaceae, a group of three New World genera, does not appear to be karyologically related to other mistletoe families; it is postulated they may be aerial parasites in the Santalaceae, which is primarily a family of terrestrial root parasites.