SYSTEMATICS OF THE SOUTH AMERICAN HYPOCHAERIS SESSILIFLORA COMPLEX (ASTERACEAE, CICHORIEAE)1

E. URTUBEY; T. F. STUESSY; K. TREMETSBERGER

ANNALS OF THE MISSOURI BOTANICAL GARDEN

Missouri Botanical Garden Press.

Lugar: Missouri; Año: 2008 p. 1 - 51

0026-6493

The Hypochaeris sessiliflora Kunth complex (Asteraceae, Cichorioideae) consists of nine species of the genus from South America (all in sect. Achyrophorus L.) that have sessile or nearly sessile flowering heads surrounded by a rosette of leaves. They occur at 1430-5100 mm elevation along the Andean chain from Venezuela to Chile and Argentina. Two species, H. sessiliflora and H. meyeniana (Walp.) Griseb., are extremely polymorphic, and they vary conspicuously in shape of the external phyllaries and presence or absence of different types of trichomes. They have the widest distributions (Venezuela to central Peru, and Peru to northern Chile and northwestern Argentina, respectively), they flower throughout the year, and they also are primarily associated with dry and sunny habitats. Hypochaeris meyeniana is characterized by retrorsely pinnatifid leaves (rarely lobate) and slightly narrower cypsela apices. Hypochaeris hohenackeri (Sch. Bip.) Domke and H. taraxacoides Ball are glabrous, whereas H. acaulis (J.Rémy) Britton has scattered shaggy trichomes on the leaves; all three occur in humid places, such as seeps or bogs. Hypochaeris eriolaena (Sch. Bip.) Reiche and H. mucida Domke are pubescent, with long whip-like trichomes on leaves and phyllaries, giving a niveo-tomentose appearance. Hypochaeris echegarayi Hieron. (white corollas) andH. eremophila Cabrera (yellow corollas) are two related species with shaggy trichomes on the abaxial surfaces of the phyllaries, and both with considerable ecological tolerance, growing in dry as well as humid sites. Morphological cladistic analyses suggest an hypothesis of relationships within the complex. Surprisingly, Hypochaeris acaulis from Chile and Argentina, although fitting morphologically within the Hypocharis sessiliflora complex, based on AFLP data seems clearly not to belong to this group. Instead, the species ties to H. palustris (Phil.) De Wild. and H. tenuifolia (Hook. & Arn.) Griseb. also from the southern Andes. The acaulescent habit of H. acaulis seems best interpreted as a parallel adaptation to survival at high elevations.