A Molecular Phylogeny of the Feathery Mistletoe Misodendrum ROMINA VIDAL-RUSSELL 1 and DANIEL L. NICKRENT Department of Plant Biology, Southern Illinois University Carbondale, Carbondale, Illinois 62901-6509, U.S.A. 1 Author for correspondence (romina@siu.edu) Communicating Editor: Sara B. Hoot ABSTRACT. Misodendrum comprises eight species of aerial hemiparasites endemic to temperate forests of Chile and Argentina that parasitize Nothofagus. This mistletoe is unique in that it has feathery staminodes on its wind dispersed achenes. Previous classifications included two subgenera, Misodendrum (two sections) and Angelopogon (three sections). The present study tested this classification using two chloroplast genes (trnL-F and matK) and 31 morphological characters. Maximum parsimony, likelihood and Bayesian analyses were performed for individual and combined partitions. Results from analyses of the separate partitions differed only in the positions of M. linearifolium and M. quadriflorum; however, the 2-gene tree gave higher support for M. quadriflorum as sister to all other species. Misodendrum brachystachyum and M. oblongifolium form a well supported clade that is sister to one composed of M. punctulatum, M. gayanum, and M. angulatum. These phylogenetic relationships generally agree with previous taxonomic classifications. Subgenus Misodendrum, characterized by warty stems and two stamens, here resolves as a polytomy: M. punctulatum, M. gayanum, and M. angulatum. Subgenus Angelopogon, characterized by the plesiomorphies three stamens and foliacious bracts, is paraphyletic given our rooting. Misodendrum brachystachyum and M. oblongifolium (section Archiphyllum) differ morphologically only by the length of their fruiting staminodes. KEYWORDS: matK, parasitic plant, Santalales, South America, trnL-F. Misodendrum Banks ex DC, the sole genus of Misodendraceae, comprises eight species of aerial hemiparasitic shrubs endemic to temperate forests from 36u 309 S in central Chile to 55u S on Tierra del Fuego Island, Argentina. These mistletoes are host specific, naturally parasitizing various species of Nothofagus (rarely parasitic on other hosts; Skotts- berg 1914). Although the range of Nothofagus extends to other Gondwanan landmasses such as Australia and New Zealand, Misodendrum is re- stricted to the New World. Misodendrum is characterized by sympodial branches with alternate leaves. Plants are dioe- cious; however, monoecious individuals are rarely found, including some with bisexual flowers. The inflorescence is basically a raceme or spike with multiple flowers, although sometimes reduced to one or two flowers. The inflorescence bracts are similar to the leaves. Flowers are very small and dull in color. Staminate flowers lack a perianth and bear two or three stamens that surround a central nectariferous disk. In the carpellate flowers the perianth and the bases of the staminodes are fused to the ovary. From the grooves formed by the edges of the perianth members, three staminodes emerge approximately midway along the ovary. After fertilization, these staminodes will develop into the characteristic feathery appendages of the fruit. In some species, perianth lobes are recogniz- able at the apex of the ovary. The nature of these lobes has not been adequately investigated, but we favor the concept that they are petals (as in Takhtajan 1997), where fusion and reduction have progressed to such a degree that no evidence of a calyx (or calyculus) exists. Because the perianth is fused to the ovary for nearly its entire length, we interpret it as epigynous, not hypogynous as stated in Orfila (1978). Because the staminodes (or sta- mens in bisexual flowers) are fused to the ovary only at the base, they could be considered epihypogynous. A nectariferous disk occurs inside the petal lobes and surrounds a short style ending in three stigmas. The unilocular ovary is tricarpel- late at the base and bears three ovules, pendulous from a free-central placenta; each has an un- differentiated nucellus and integument. Following ovular abortion, only one seed remains in the mature fruit. The presence of nectary disks on flowers of both sexes, in conjunction with char- acteristics of the pollen exine, suggest insect pollination (Orfila 1978), although empirical data are lacking. In the Lake Vintter area of Argentina, Orfila (1978) observed many adult Cantharidae (Coleoptera) on flowering Misodendrum. These beetles are known to eat petals and stamens and Orfila (1978) states that they could be involved in pollinating Misodendrum. The fruit is a wind dispersed achene with three feathery appendages of varying length depending upon the species. The appendages not only keep the fruit aloft but also aid in attachment to the host branch. Upon germination, the green hypocotyl with a sticky apical holdfast adheres to the host branch. The radicle develops an haustorium that first attaches to the host epidermis and then enters the cortex. The haustorium branches out and Systematic Botany (2007), 32(3): pp. 560–568 # Copyright 2007 by the American Society of Plant Taxonomists 560