ZOMLEFER, WENDY B.1*, NORRIS H. WILLIAMS2, W. MARK WHITTEN2, and WALTER S. JUDD3. 1University of Georgia, Dept. of Botany, 2502 Plant Sciences, Athens, GA 30602-7271; 2University of Florida, Florida Museum of Natural History, Dept. of Natural History, P.O. Box 117800, Gainesville, FL 32611-7800; 3University of Florida, Botany Dept., P.O. Box 118526, Gainesville, FL 32611-8526. - The genera of Melanthieae (Liliales, Melanthiaceae): circumscription and relationships based on ITS and trnL-F sequence data.
The little-studied tribe Melanthieae is a group of temperate
"petaloid lilioid monocots"—so named for their small
lily-like flowers with petal-like tepals. Defining genera has been
more problematic for these superficially similar plants than for most,
if not all, other monocots. Until our current analyses, the
circumscriptions of the constituent core genera of the Melanthieae
(Amianthium, Schoenocaulon, Stenanthium,
Veratrum-Melanthium, Zigadenus s.l.) had not been the
subjects of rigorous phylogenetic character analyses, and their
intergeneric relationships were also unresolved. The circumscription
and relationships of these genera (29 representative taxa) were
evaluated using parsimony analyses of ITS (nuclear ribosomal) and
trnL-F (plastid) DNA sequence data. Based on the molecular
cladograms, Stenanthium is biphyletic, and the traditional
Zigadenus s.l. is polyphyletic. Amianthium and
Schoenocaulon are distinct entities; the Veratrum
complex is conservatively treated as one large monophyletic genus
(including Melanthium). Although some intergeneric
relationships are not highly resolved, the analyses provide strong
support for Zigadenus glaberrimus as sister to the rest
of the tribe, and Amianthium muscitoxicum as closely
related to Veratrum s.l. As a result of this study, seven
genera (some with novel circumscription) are recognized within the
tribe Melanthieae: Amianthium, Anticlea,
Schoenocaulon, Stenanthium, Toxicoscordion,
Veratrum, and Zigadenus. These generic circumscriptions,
strongly supported by the tree statistics and topologies in all
analyses, are correlated with potential morphological synapomorphies
(at the proper level of universality). The study includes practical
recommendations, such as documentation of diagnostic characters to be
ultimately used in keys and descriptions. Such features include
rootstock type, bulb shape, inflorescence structure, indumentum type,
tepal shape, nectary morphology, and ovary position.
Key words: ITS, Melanthiaceae, Schoenocaulon, trnL-F, Veratrum, Zigadenus