Alpine vegetation is scarce in central Mexico (≈150 km2) and occurs on the 11 highest peaks of the Trans-Mexican Volcanic Belt (TMVB). Timberline occurs at (3700) 3900 m, and at 4750 m vascular plants cease to exist. The alpine vascular flora comprises 237 species from 46 families and 130 genera. Asteraceae (44), Poaceae (42), and Caryophyllaceae (21) possess 45% of the species; none of the remaining families have more than 10 species. Four species are strict endemics, and eight others are near endemics. Thirteen species are restricted to alpine vegetation but also occur outside the study area. Seventy-seven species are endemic to Mexico, 35 of which are endemic to the TMVB. In terms of biogeography, the strongest affinities are with Central or South America. Fifteen species are also native to the Old World. Size of the alpine area seems to not be the determining factor for its floristic diversity. Instead, the time since and extent of the last volcanic activity, in addition to the distance from other alpine islands, appear to be important factors affecting diversity. There is evidence for upward vegetational shifts having occurred during the last century.

Abstract—The genus Hechtia includes 84 species, 79 of them present in Mexico. With 12 species (including those described herein), the Mexican state of Guerrero is the third most diverse in species. As a result of botanical explorations for the project Bromeliaceae of Mexico, we describe here five new species for science, all endemic to Guerrero: Hechtia elegans, H. ensifolia, H. medusae, H. platyphylla, and H. pycnostachya. The proposed species are compared with other morphologically similar taxa (H. caulescens, H. flexilifolia, H. glauca, H. hintoniana, H. laxissima, and H. pretiosa). Morphological descriptions, images, and a distribution map of the described taxa are included, as well as an identification key for all the species of Hechtia currently known from Guerrero.

Tillandsia religiosa Hern.-Cárdenas, González-Rocha, Espejo, López-Ferr., Cerros & Ehlers, a new species from Morelos, Mexico is described and illustrated. The new species is compared to taxa with similar characteristics, T. taxcoensis Ehlers, T. thyrsigera E. Morren ex Baker and T. superinsignis Matuda. Images and a distribution map of the new taxon are included.

El área de estudio, la Barranca Tepecapa de aproximadamente 3.5 km de longitud, se ubica dentro de la zona núcleo “Las Mariposas” en el Corredor Biológico Chichinautzin del estado de Morelos. Se realizaron colectas periódicas durante un año y medio, de octubre 2009 a abril 2011. Se colectaron 1018 ejemplares de Pteridofitas y afines, Gimnospermas y Angiospermas, pertenecientes a 99 familias, 266 géneros y 434 especies. Las familias mejor representadas son: Asteraceae, Fabaceae, Poaceae, Orchidaceae, Pteridaceae, Solanaceae y Bromeliaceae. Asimismo, se registran y describen tres tipos de vegetación para el área de estudio. Dos géneros (Amyris y Dasylirion) y 16 especies son nuevos registros para el estado de Morelos.

Taxonomía y sistemática Revisión taxonómica del género Viridantha (Tillandsia subgénero Viridantha sensu stricto) Taxonomic revision of the genus Viridantha (Tillandsia subgenus Viridantha sensu stricto)

Hechtia gypsophila and H. minuta, two new species from Oaxaca, Mexico are described and illustrated. The proposed species are compared with H. pumila, taxon that present some similarities and also with other species that grow near the type localities of the two new taxa proposed. Images and a distribution map of all taxa are included.

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Tillandsia bernalensis, a new species from the state of Querétaro, Mexico, is described and illustrated. The proposed species is compared to T. parryi, T. suesilliae and T. tonalaensis, taxa with some similarities. Images and a distribution map of the four species are included.