Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

Pitcairnia yocupitziae Espejo & López-Ferrarri, sp. nov. (Bromeliaceae), known only from the state of Guerrero, Mexico, is described and illustrated. The new species is compared with P. roseana L. B. Sm., from which it differs by its inflorescence and floral bracts. An identification key for the species of Pitcairnia present in Guerrero is also included.

In this research an in vitro technique was developed for production and propagation of intergeneric hybrids from immature seeds produced by crossing the domestic sunflower Helianthus annuus and the wild species Tithonia rotundifolia (Mill.) S. F. Blake. For embryo rescue in tissue culture the greatest success was obtained with the sequential use of three Murashige-Skoog based media: a) with amino acids and growth regulator BAP for germination, b) without amino acids and with BAP for micropropagation, and c) without vitamins and growth regulator ANA for root development. The amino acids were added as a source of organic nitrogen. From a single seedling a total of 130 healthy plantlets were obtained. Twenty of them were taken for acclimatization, and only one reached an incomplete flowering stage. Therefore, standardizing acclimatization conditions is still required. In particular, it is necessary to establish treatments that allow a clear definition of the specific conditions for the acclimatization of the hybrid, through the test of different substrate mixtures and nutritive solutions under controlled environmental conditions. It is recommended to try the use of retardants and amino acids, as well as modifications in light intensity.

We reassessed the extinction risk of the species Polianthes densiflora, P. howardii, P. longiflora, P. palustris and P. platyphylla by applying the MER (method of evaluation of extinction risk of wild species for Mexico). These species are listed as rare by the International Union for Conservation of Nature (IUCN) and are considered to be in the category of special protection according to Mexican regulation. MER criterion A (geographic distribution) was assessed with three methods: area of occupancy, extent of ocurrence, and species distribution models. Criteria B (habitat conditions) and D (impact of human activity) were examined by superimposing the human footprint map of Sanderson et al., where values range from 0 to 100. In this map, 0-10 denote pristine areas and 100 indicates that the habitat has been completely transformed. Criterion C (intrinsic biological vulnerability) was assigned based on the geophytic nature of the species. According to our findings, Polianthes densiflora and P. longiflora are in danger of extinction, while P. howardii and P. platyphylla are endangered and P. palustris is likely extinct. None of the five species concerned occur in any Natural Protected Area. We propose in situ and ex situ strategies to maintain these species as well as the development of programs of sustainable use for Polianthes longiflora and P. platyphylla. These species could be cultivated and domesticated by means of vegetative propagation.

Se describe e ilustra una nueva especie de Burseraceae. Bursera xolocotzii es un árbol del bosque tropical caducifolio, conocido sólo de los alrededores de la presa de Infiernillo en los estados de Michoacán y Guerrero. La especie forma parte de la sección Bursera, destaca por sus hojas unifolioladas glabras, el aroma fuerte y persistente de la resina de las hojas y ramillas jóvenes, sus flores femeninas trímeras a tetrámeras, las masculinas tetrámeras a trímeras excepcionalmente pentámeras y el carácter de su corteza gris, lisa, no exfoliante. Presenta similitudes con Bursera laurihuertae Rzed. & Calderón y con B. lunanii (Spreng.) C. D. Adams & Dandy ex Proctor.

In the central area of the State of Chihuahua, 135 field trips for collecting almost 6500 plant specimens were made in six years. A herbaria and bibliographic review and a study of the flora of the plains and low hills was also carried out. We recorded 112 families, 493 genera, 1322 species, and 232 infraspecific taxa of vascular plants. Of the total families, 87 were dicotyledons, 15 monocotyledons, 7 ferns and allies, and 3 conifers and allies. The families with highest number of genera and species were: Asteraceae (86, 235), Poaceae (50, 163), Leguminosae (45, 137), Brassicaceae (16, 25), Malvaceae (12, 29), Scrophulariaceae (11, 29), Cactaceae (10, 30), Verbenaceae (10, 24), Nyctaginaceae (7, 21) and Amaranthaceae (7, 18). The genera with highest number of species were: Muhlenbergia (37), Dalea (22), Euphorbia (21), Cheilanthes (19), Brickellia (17), Salvia (15), Cyperus (14), Quercus (13), Solanum (12), Eragrostis (12), Bouteloua (12), Erigeron (12), Astragalus (11), Ipomoea (11), Plantago (10), Acacia (10), Machaeranthera (9), Stevia (9), Opuntia (9), Aristida (9), Asclepias (9), Phaseolus (9), Oenothera (9), Viguiera (9) and Notholaena (9).The present study is a contribution to the knowledge of plant diversity in the arid lands of northern Mexico.

The morphologic variation of the genus Prochnyanthes was analyzed by means of the examination of 29 characters, in a sample of 544 individuals from 19 localities. The Principal Components Analysis was used, which shows the variation trends, analyses the similarities among the classification units and identifies groups. Based on the morphological evidence, it was possible to recognize two phenotypes, considered as extremes of a morphological cline. Therefore, the morphological species concept of P. mexicana was broaden to include all the variation observed. Finally, the size and color of the perianth and the length of the pedicels did not show enough variation to identify groups and consequently P. mexicana is the only recognized species of the genus.

A new species, Hypoxis colliculata from Oaxaca and Chiapas, México is presented here. It belongs to the group with black seeds and is separated from the other species by the colliculate sculpturing of the seeds.

Based on collections gathered in the Mexican states of San Luis Potosí, Guanajuato and Querétaro, Verbesina abietifolia, V. carranzae, V. steinmannii, and V. suberosa are described as new species and illustrated.

Simsia bicentenarialis from northeastern and central Queretaro and northeastern Guanajuato is described as new and illustrated. It shows similarities with some varieties of S. foetida (Cav.) S. F. Blake.

Bio.