Zeltnera is a genus of about 25 species of annual, biennial, and short-lived perennial herbs in the gentian family, Gentianaceae (order Gentianales). The genus was established in 2004 when molecular phylogenetic analysis showed that the older genus Centaurium was polyphyletic — composed of four distinct lineages that are now treated as separate genera. The Eurasian species were retained in Centaurium, Mexican species were placed in Gyrandra, Mediterranean and Australian plants moved to Schenkia, and the predominantly North American centauries were grouped under the new name Zeltnera.
Plants in the genus are taprooted or fibrous-rooted, with one or more branching stems that are often ridged and sometimes winged. Leaves range from linear to lance-shaped to oval, are green or yellowish, and may be gathered near the base or distributed along the stem. The flowers are characteristically tubular at the throat, opening into a flat, spreading corolla of four or five lobes in shades of pink or white; the throat is usually paler, often white or yellowish. The fruit is a small capsule that may contain up to 700 minute seeds. Zeltnera and Centaurium are most readily distinguished by differences in style and stigma morphology and by capsule shape.
The genus can be informally divided into three geographic groups supported by DNA evidence: a "Californian group" ranging from British Columbia south along the West Coast of North America to Baja California; a "Texan group" occurring from Arizona and Oklahoma into northern Mexico; and a "Mexican group" distributed through Mexico, Central America, and into parts of South America, with its northern limits potentially reaching Arizona. Altogether GBIF recognizes 29 accepted taxa in the genus. Notable members include Zeltnera venusta (charming centaury or canchalagua), Zeltnera texensis (Lady Bird's centaury), Zeltnera beyrichii (quinineweed), and Zeltnera calycosa (Arizona centaury).
Etymology
Zeltnera was named in honor of the Swiss botanists Louis and Nicole Zeltner, who made significant contributions to research on Centaurium and other members of the gentian family (Gentianaceae).
Distribution
The genus is concentrated in the Americas, with three informal geographic groups: western North America from British Columbia to Baja California; south-central North America from Arizona to Oklahoma and into northern Mexico; and a southern group extending through Mexico, Central America, and into parts of South America.
Taxonomy Notes
Zeltnera was erected in 2004 following molecular phylogenetic evidence that Centaurium as traditionally circumscribed was polyphyletic. The split produced four genera: Centaurium (Eurasian species), Gyrandra (Mexican species), Schenkia (Mediterranean and Australian species), and Zeltnera (mainly North American species). Within Zeltnera, three informal subgroups — the Californian, Texan, and Mexican groups — are recognized on geographic and molecular grounds. GBIF places the genus in family Gentianaceae, order Gentianales.
