Wednesday, July 18, 2018

[Botany • 2018] Thelocactus tepelmemensis (Cactaceae) • A Distinctive New Species of Thelocactus from Oaxaca, Mexico

Thelocactus tepelmemensis T.J. Davis, H.M. Hern., G.D. Starr & Gómez-Hin.

in Davis, Hernández, Starr & Gómez-Hinostrosa, 2018.
Tepelmeme Cliff Cactus  ||  DOI: 10.11646/phytotaxa.361.1.10 

Thelocactus tepelmemensis, a distinctive new species of Cactaceae from northern Oaxaca, Mexico, is described and illustrated. The new species is closest to T. leucacanthus but differs significantly from this and other species in the genus by a combination of morphological characters: smaller, red-purple flowers; stems with ribs consistently vertical; lower number of spines per areole, these being usually shorter; ovoid fruit; and seeds with conjunct micropyle. The new species is found in a narrow canyon growing on steep limestone rock faces protected from direct afternoon sun. The only known population appears to be locally common but geographically restricted. 

Keywords: endemic, Oaxaca, Tehuacán-Cuicatlán Biosphere Reserve 

Figure 2. Thelocactus tepelmemensis (body, flower, and fruit) and its habitat.
A. Caespitose individual with several lateral stems (Type). B. Vertical limestone wall with several individuals. C. External aspect of a flower (above); dissected flower showing the internal perianth segments, the stamens, and the gynoecium (middle); and, semi-mature fruit with persistent perianth (below). Voucher: H.M. Hernández et al. 4128 (MEXU).

Figure 1. Thelocactus tepelmemensis. A. Stem with flower. B. Areoles. C. Flower (lateral view and dissected). D. Fruit. Voucher: H.M. Hernández et al. 4128 (MEXU). Drawn by Albino Luna.

Thelocactus tepelmemensis T.J. Davis, H.M. Hern., G.D. Starr, and Gómez-Hin., sp. nov. 

Diagnosis:— Similar to Thelocactus leucacanthus, but differing in having a lower number of spines per areole, these being poorly differentiated into radials and centrals (vs. more and readily differentiated spines); by the much smaller, red-purple flowers (vs. larger yellow or magenta flowers); and, the conjunct seed micropyle lying inside the hilum border (vs. disjunct micropyle lying outside border). 

Type:— MEXICO. Oaxaca, municipality Tepelmeme, 17 January 2018 (fl., fr.), H.M. Hernández et al. 4128 (holotype: MEXU 1471315!; isotypes: DES!, MEXU 1471316!). (Figures 1–3)


Etymology:— The specific name refers to the community of Tepelmeme Villa de Morelos in whose territory the new species is currently known. 
The suggested English (Tepelmeme cliff cactus) and Spanish (Biznaga de acantilado de Tepelmeme) names refer to the species’ cliff habitat and the community of Tepelmeme Villa de Morelos.

Tristan J. Davis, Héctor M. Hernández, Greg D. Starr and Carlos Gómez-Hinostrosa. 2018. A Distinctive New Species of Thelocactus (Cactaceae) from Oaxaca, Mexico. Phytotaxa. 361(1);  115–122. DOI: 10.11646/phytotaxa.361.1.10 

Resumen: Se describe e ilustra Thelocactus tepelmemensisuna nueva especie de Cactaceae del norte de Oaxaca, México. La nueva especie está cercanamente relacionada a T. leucacanthus, pero difiere de ésta y otras especies del género por una combinación de caracteres morfológicos, en particular por tener flores más pequeñas, de color rojo-púrpura; los tallos con costillas consistentemente verticales; el número más bajo de espinas por areola, siendo éstas usualmente más cortas; el fruto ovoideo; y las semillas con el micrópilo conjunto. La nueva especie se localiza en un cañón estrecho creciendo sobre paredes verticales de calizas protegidas del sol vespertino. La única población conocida parece ser relativamente densa, pero restringida geográficamente. 

Palabras Clave: endémica, Oaxaca, Reserva de la Biosfera Tehuacán-Cuicatlán