Carlos Gómez-Hinostrosa

Diversity, spatial arrangement, and endemism of Cactaceae in the Huizache area, a hot-spot in the Chihuahuan Desert

We studied several aspects of the cactus diversity in the Huizache, an area located in the southern extreme of the Chihuahuan Desert Region, in San Luis Potosí, Mexico. Fieldwork was conducted in a square-shaped polygon (22°30′–23°00′ N, 100°00′–100°30′ W), where a total of 80 systematically-chosen localities were sampled for cactus species. Results showed that the Huizache is an important focal point for the conservation of the Cactaceae, due to the remarkably high diversity of members of this plant family in the area. With 75 species recorded, this area has the highest concentration of cactus species in the American Continent, in comparison with other comparably-sized regions. The outstanding diversity of cactus species in the Huizache area may be explained by the relatively favorable climate of this desert area, its environmental heterogeneity, and its location in a transitional position between three regions with distinct cactus floras: Chihuahuan Desert Region, Queretaroan-Hidalgoan Arid Zone, and Tula-Jaumave Valleys. Species richness is not distributed evenly in the area; the zones of highest species concentration are primarily located in the lowland valleys, in the northwestern portion of the grid square, where typical Chihuahuan Desert conditions prevail. Of the 75 cactus species found in the area, 63% are endemic to the Chihuahuan Desert. Among these, ten species are outstanding for being endemic or nearly endemic to the Huizache area. The Huizache grid square is part of a recently declared natural reserve, The Real de Guadalcázar Natural Reserve.

Diversity, geographical distribution, and conservation of Cactaceae in the Mier y Noriega region, Mexico

We carried out an inventory of the cactus species occurring in the Mier y Noriega region. The study was conducted in a square-shaped area of approximately 2845 km2, located in the southeastern segment of the Chihuahuan Desert region, between 23°00′ – 23°30′ lat. N and 100°00′ – 100°30′ long. W, including parts of the states of Nuevo León, Tamaulipas, and San Luis Potosí, Mexico. In order to know the cactus diversity, we developed an intensive method of botanical collecting; a total of 80 sites were sampled. With 54 species recorded, of which 28 were new area records and 14 new state records, the Mier y Noriega region is considered moderately rich in cactus species. Cactus diversity is distributed unevenly in the area, and the greatest species concentration occurs in its southwestern portion. The analysis of geographical distribution of individual species showed that the highest proportion (82%) are endemic to the Chihuahuan Desert Region, six of them having extremely narrow distributions. In addition, 19 species are considered endangered. With the aid of a complementarity analysis, we propose a strategy for the optimal conservation of the species and their habitats.

Areas of endemism of Cactaceae and the effectiveness of the protected area network in the Chihuahuan Desert

We used distribution data of 121 cactus species endemic to the Chihuahuan Desert to test the effectiveness of the regions protected area network. The analysis of species distribution using a 309 latitude 3 309 longitude grid facilitated the identification and categorization of areas of endemism. We found a low degree of coincidence between protected areas and the areas of cactus endemism, and only 63.6% of the 121 species occur in protected areas. A comple- mentarity analysis showed that 10 of the protected areas contain the 77 species that occur in protected areas. The four top priority areas protect 65 (84.4%) of these 77 species The 44 unprotected species are mainly micro-endemic and taxonomically distinctive taxa widely scattered in the region. The complementarity analysis applied to these species showed that all of them can be contained in a minimum of 24 grid squares, representing 32.9% of the total area occupied. Their strong spatial dispersion, along with their narrow endemism, is a major conservation challenge. We conclude that the current protected area network is insuffi- cient to protect the rich assemblage of cacti endemic to the Chihuahuan Desert. Conservation efforts in this region should be enhanced by increasing the effectiveness of the already existing protected areas and by the creation of addi- tional protected areas, specifically micro-reserves, to provide refuge for the unprotected species.

Studies on Mexican Cactaceae. IV. A new subspecies of Echinocereus palmeri Britton & Rose, first record of the species in the Chihuahuan Desert

Summary: Echinocereus palmeri subsp. mazapil, a new subspecies of Cactaceae from the Chihuahuan Desert Region, Mexico, is described and illustrated. It has only been collected from a highly specialized habitat at two remote localities in the state of Zacatecas and its range is markedly disjunct from that of the typical subspecies. In addition to divergences in geographic range and habitat preferences, E. palmeri subsp. mazapil differs from the typical subspecies by usually having relatively smaller stems with tuberculate ribs and less numerous radial spines, which usually are of unequal length.

Studies on Mexican Cactaceae. II. Opuntia megarrhiza, a poorly known endemic from San Luis Potosí, Mexico

Opuntia megarrhiza Rose (Cactaceae) is a species endemic to central San Luis Potosí, Mexico that, since originally described in 1906, has remained poorly understood. A comprehensive morphological description is presented and its presumed taxonomic affinity withO. chaffeyi is discussed. General accounts of its distribution, ecology, uses, and conservation status are presented.ResumenOpuntia megarrhiza Rose (Cactaceae) es una especie endémica de la porción central de San Luis Potosí, México, que, desde que fue descrita originalmente en 1906, ha permanecido pobremente entendida. Se presenta una descripción morfológica detallada y se discuten sus supuestas afinidades taxonómicas conO. chaffeyi. Se delinean algunos datos sobre su distribución, ecología, usos y estado de conservación.

Studies on Mexican Cactaceae. V. Taxonomic notes on Selenicereus tricae

Selenicereus tricae is a poorly known species from Belize, Guatemala, and Mexico. We present a morphological and anatomical description of this plant and provide data on its habitat and geographical distribution. In addition, we discuss its taxonomic affinities with S. inermis, S. wercklei, and S. rubineus, its hypothetical closest relatives. Selenicereus tricae has already been combined with S. inermis, as subsp. tricae, and two new combinations are proposed here: S. inermis subsp. rubineus and S. inermis subsp. wercklei. The presence in S. inermis subsp. tricae of diagnostic morphological and anatomical features of Selenicereus and Hylocereus suggests that these two genera should probably be merged.ResumenSelenicereus tricae es una especie de Belice, Guatemala y México poco conocida. Se presenta una descripción morfológica y anatómica detallada, y se aportan algunos datos sobre su hábitat y distribución geográfica. Además, se discuten sus afinidades taxonómicas con S. inermis, S. wercklei y S. rubineus, sus supuestos parientes más cercanos. Selenicereus tricae ha sido ya combinada justificadamente con S. inermis, como subsp. tricae, y se proponen aquí dos nuevas combinaciones: S. inermis subsp. rubineus y S. inermis subsp. wercklei. La presencia en S. inermis subsp. tricae de caracteres morfológicos y anatómicos diagnósticos de Selenicereus e Hylocereus sugieren que estos dos géneros podrían ser fusionados.

Studies on Mexican Cactaceae. VI. A new species of Weberocereus (Cactaceae) from Oaxaca, Mexico

Weberocereus alliodorus, a new cactus species from the southern slopes of the Sierra Madre del Sur, Oaxaca, Mexico, is described, illustrated, mapped, and compared to its putative closest relative, W. glaber. The new species is characterized by its three-winged stems with rigid and setose, relatively long spines, relatively large flowers, and fruits with a penetrating onion-like odor.ResumenSe describe, ilustra y mapea a Weberocereus alliodorus, una nueva especie de cactus de Oaxaca, México, y se compara con W. glaber, su supuesto pariente más cercano. La especie nueva se caracteriza por sus tallos trialados con espinas rígidas y setosas relativamente largas, por sus flores relativamente grandes y por sus frutos con un olor penetrante reminiscente a la cebolla.