A NEW ANNUAL SPECIES OF CHAENACTIS (COMPOSITAE) FROM THE CENTRAL DESERT OF BAJA CALIFORNIA, MEXICO

Abstract

A new yellow-flowered annual pincushion, Chaenactis kyhosii B.G.Baldwin, is described from the Central Desert of Baja California, Mexico. This desert taxon has been confused with C. glabriuscula DC. sensu lato (s. l.), a species complex of the California Floristic Province and desert periphery. Chaenactis kyhosii (2n = 5II) is evidently allopatric with C. glabriuscula s. l. (2n = 6II) and is distinct chromosomally. It differs morphologically from other yellow-flowered members of Chaenactis, including C. glabriuscula s. l., by the character-state combination of having non-glandular hairs sparse or lacking, main stem branches concentrated at or near base, leaves mostly basal or proximal on stems, leaf blades entire and filiform or once-pinnate with filiform lobes, peduncles and involucres densely glandular, corollas of marginal florets only slightly enlarged, cypselae sparsely white-strigose to ± glabrate, and pappi uniseriate, of four well-developed, generally unequal, and often obtuse scales. Chaenactis kyhosii is more closely related to the white-flowered, primarily desert-dwelling annual C. fremontii A.Gray, also with 2n = 5II, and the southern lineages of C. glabriuscula s. l. than to the northern lineages of C. glabriuscula s. l.