IPOMOEA TEHUANTEPECENSIS (CONVOLVULACEAE): A NEW SPECIES FROM THE ISTHMUS OF TEHUANTEPEC, MEXICO

A new and narrowly endemic species from the Tehuantepec District of Oaxaca, Ipomoea tehuantepecensis L. Torres Colin, R. Torres Colin, M.P. Ramirez & J.A. McDonald, is described and illustrated. The new species belongs to a primitive assemblage of hairy-seeded lianas (I. subg. Eriospermum Verdc.) that exhibit specialized red and hypocrateriform corollas with exserted reproductive structures (Ipomoea ser. Mirandinae D.F. Austin). Ipomoea tehuantepecensis shares numerous morphological traits with I. concolora (Matuda) D. Austin and I. conzattii Greenm. in arid regions of southern Mexico but differs by glabrous laminas with obtuse to subcordate leaf bases, pleiocasial cymes, glabrous pedicels less than 6 mm long, glabrous sepals from 4–4.5 mm long and 2–3 mm wide, and glabrous corollas up to 3.0 cm long. In contrast, I. conzattii and I. concolora present pubescent laminas with cordate or truncate-obtuse leaf bases, monochasial cymes, pubescent pedicels from 7–15 mm long, sericeous sepals from 5–8 mm long, and pilose or sericeous corollas from 3.0–4.5 cm long.