New Taxa in Verbesina (Sect. Verbesinaria) from North-Central Mexico

Abstract

-Two new taxa, Verbesina daviesiae and a variety of V. hypomalaca, both belonging to the Sect. Verbesinaria, are described. The former is an eglandular taxon restricted to mountainous gullies near Saltillo, while the latter is a widespread glandular species composed of three varieties, one of which, var. saltillensis, is described as new. Recent exploration in north-central Mexico has revealed the presence of an hither-to uncollected new species of Verbesina. In pursuit of its identity I was obliged to study the infraspecific variation in V. hypomalaca Rob. & Greenm., its most closely related taxon. Verbesina daviesiae B. L. Turner, sp. nov.V. hypomalaca accedens sed pilis paucioribus eglandularibusque, laminis foliorum non bullatis, floribus disci majoibus faucibus glabris. Perennial herb to 130 cm height, the stems erect, purplish below, sparsely soft-pubescent with white hairs. Leaves alternate throughout, or nearly so; petioles 1-2 mm long; blades broadly lanceolate, 50-90 mm long, 15-25 mm wide, eglandular, remotely and irregularly dentate to nearly entire, sparsely semi-appressed pubescent below, evenly and moderately coarse-pubescent above. Capitulescence terminal, 5-9 headed in pseudo-umbellate cymes. Heads broadly turbinate, 6-8 mm across, ca. 8 mm high. Receptacle conical. Chaff ovate, acute, yellowish, sparsely ciliate. Ray florets 8, yellow; ligules 9-11 mm long, 4-5 mm wide; tube ca. 2 mm long, glabrous or nearly so. Disc florets yellow, 4-5 mm long; tube ca. 1 mm long, sparsely pubescent; throat 3-4 mm long, glabrous or nearly so; lobes glabrous, ca. 0.75 mm long. Anthers black, ca. 2 mm long; appendages 0.5 mm long. Achenes biaristate, obovate, black, sparsely pubescent with appressed hairs, narrowly winged below, more so above, the wings ciliate and extending up the aristae for ca. 0.5 mm. Type: MEXICO: Coahuila: 15 mi E Saltillo. Confined to gullies along upper mountain slopes. 21 Aug 1979. F. Davies & B. L. Turner A78. (Holotype, TEX; isotype, MEXU) It is a pleasure to name the species for Dr. Frances Davies of the Royal Botanical Garden, Kew, England, who participated in its discovery. Verbesina daviesiae occurs in the general region with V. hypomalaca var. saltillensis and superficially resembles it. However, the latter, which occurs on open or forested limestone slopes dominated by pines, is much more abundant. Verbesina daviesae is a more robust, totally eglandular plant which seemingly is confined to more mesic sites, along montane arroyos, etc. It is clearly rare, only a single population being noted at the site named, this composed of but a few plants. Verbesina daviesiae is related to V. hypomalaca and V. hypomalaca var. saltillensis and could possibly have arisen by ancestral hybridization, since V. hypomalaca varies in the direction of V. daviesiae over a broad region within the area bounded by the triangle, Saltillo-Monterrey-Pefia Nevada. Verbesina hypomalaca Robinson & Greenman, var saltillensis B. L. Turner,