The Taxonomy of Carex sect. Hymenochlaenae (Cyperaceae) in Mexico and Central America

Abstract

Carex (Cyperaceae) sect. Hymenochlaenae comprises 13 Mexican and Central American species. The section is defined broadly to include species formerly placed in sects. Longirostres, Sylvaticae, and Viridiflorae. Three new species are described, C. brunnipes, C. flexirostris, and C. ixtapalucensis. The names C. pertenuis and C. viridis are lectotypified and lectotypes are chosen for sects. Hymenochlaenae and Longirostres. Section Hymenochlaenae is distinguished from all others by: perigynia usually more or less trigonous or even orbicular in cross section, never strongly flattened; perigynium apices entire, erose, or obscurely bidentulate; several to many elongate-cylindric spikes usually pendulous on filiform, flexuous peduncles; and leaf-like, sheathing inflorescence bracts. The section is distributed from northeastern Mexico to western Guatemala. Habitats are moist montane forest, wet meadows, and stream banks at 1500-3700 m. Carex L. is the largest genus of the Cyperaceae, with 1500-2000 species. It is best developed in temperate and, to a lesser extent, montane tropical regions. In Mexico and Central America, slightly over 100 species in about 32 sections are presently known. As defined here, sect. Hymenochlaenae (Drejer) L. Bailey includes Mexican and Central American species placed by Mackenzie (1935) and Hermann (1974) in sects. Longirostres (Kiik.) Mackenzie, Sylvaticae Rouy, and Mackenzie (Carex sect. Viridiflorae is not validly published since a Latin description was not provided). Thirteen species are recognized, making sect. Hymenochlaenae the largest one in Mexico and Central America. Section Hymenochlaenae, defined broadly in this way includes about 30 species in North and Central America. About 28 additional species occur in Eurasia and adjacent North Africa, with apparently one species endemic to East Africa. No representatives are known from South America or Australasia. Mexican and Central American species of sect. Hymenochlaenae are poorly represented in herbaria. Several species are known only from holotypes and only one species, Carex brunnipes Reznicek, is known from more than a half dozen collections. The descriptions and key therefore are based on small samples. This lack of specimens may in part be due to botanists overlooking sedges in the course of general collecting. Nevertheless, it is also clear that all these species are comparatively rare plants. Attempts to locate populations are frequently unsuccessful. Even where a species is found, the population is often small and widely dispersed.