The Tacaná-Boquerón region (TBR) in Chiapas is considered an area of high biodiversity in Mexico, with a rich but poorly studied orchid flora, which is an important component of the vegetation and threatened by an accelerated rate of deforestation. By means of fieldwork, and the revision of scientific collections and literature, an orchid checklist for the TBR and adjacent areas was made; using geographic information systems the distribution of this orchid flora was analyzed in the study area. From 1,235 records we report 105 genera and 325 species, two of them determined to infraspecific level and two are natural hybrids; nine species were additions to the Mexican flora; 39 species are considered at risk in Mexico; the national distribution of a further 20 species are restricted to the TBR. This orchid flora represents 24 % and 44 % of the national and state orchid species richness, respectively, is the second richest in Mexico, and only surpassed by the region El Momón-Las Margaritas-Montebello (Chiapas). The greatest orchid richness is concentrated between elevations of 500 to 2,499 m, in areas now given over to permanent agriculture (including coffee and cocoa plantations); in primary forest the richness is lower. The Tacaná Volcano Biosphere Reserve is the only protected area in the TBR and the proposal to extend it to the Boquerón peak would promote the protection of the orchid flora growing above 1,000 m in the region. Traditional coffee plantations could be alternative to conserve orchids that grow below 1,600 m.

Orchids establish symbiosis with Rhizoctonia mycorrhizal fungi, forming the characteristic pelotons within the cells of the root cortex. Under natural conditions, terrestrial and epiphytic orchids have different levels of dependence upon the fungal symbiont, although various authors have mentioned that once orchid plants reach maturity the interaction becomes weaker and intermittent. Recent evidence shows that in some epiphytic orchid species mycorrhization is constant and systematic. In three species of wild orchids from southeast Mexico, we show that mycorrhization is systematically present in roots of different ages, in the wet and dry seasons. We demonstrate that the volume of the root that is colonized depends upon the quantity of rainfall and the diameter of the root, and that rainfall also determines the presence of fresh, undigested pelotons. In very thin roots, mycorrhizal colonization occupies a considerable proportion of the cortex, whereas in thicker roots the proportion of the volume of the root cortex colonized is lower

In the Mexican economy, particularly in the Soconusco region of Chiapas, the cultivation of coffee generates significant inputs; however, coffee plants are susceptible to pests and diseases, so it is necessary to reinforce its production through sustainable management. In this study, we searched for the native arbuscular mycorrhizal fungi (AMF) that could be used as biofertilizers in coffee cultivation. We collected 21 soil samples coming from seven coffee plantations (Coffea canephora) in the Soconusco region Chiapas, Mexico in November 2015. We isolated the spores of AMF by the wet sieving and decanting method to quantify their abundance, richness and composition of morphospecies, as well as their relationships with soil properties. A total of 20 morphospecies and five new records of AMF were obtained, and the most frequent genera were Acaulospora and Glomus. The Toluca and Victoria sites had higher morphospecies richness (17 spp. c/u) than San Agustín, November 20 and San Luis Nexapa (4-7 spp. c/u); while Providencia and Platanar sites recorded an intermediate richness and the highest values of spore abundance. The dissimilarity of Victoria and Toluca in its composition of AMF, respect to the other sites, was explained by the low concentration of PO4-3 in the soil. P availability, linked to soil acidity, is the factor that could be regulating the AMF communities in the soil of the rhizosphere of coffee trees at Soconusco. We consider that could have consortia of AMF specific for soil P-levels and acidity of coffee sites, i.e. Acaulospora and Glomus consortia, which are common into the environmental conditions of coffee plantations in México. Anyway, we need to examin deeply these strains to evaluate their compatibility and functionality before proposing them as native biofertilizers that promote the development and yield of coffee plantations in this tropical region of Mexico.

Antecedentes y Objetivos: El café genera importantes ingresos en el mundo y en particular en Chiapas, México. Sin embargo, su producción podría mejorarse usando hongos micorrizógenos arbusculares (HMA) en lugar de sustituir una especie de cafeto por otra, como ocurre en México. En este trabajo se estimó la diversidad de HMA en plantaciones de Coffea arabica y su relación con el suelo en el volcán Tacaná, en la región del Soconusco, Chiapas. Métodos: Se recolectó suelo rizosférico en cinco plantaciones (Peloponeso, Montecristo, Chiquihuites, Finca Perú-París y Barrio Nuevo) de C. arabica. Las espo­ras de HMA fueron extraídas por tamizado húmedo y decantación, y montadas en alcohol polivinílico en lactoglicerol, con y sin reactivo Melzer. Las morfoespe­cies de HMA fueron identificadas por morfología de las esporas y su abundancia, riqueza y diversidad estimadas y asociadas con algunas propiedades edáficas. Resultados clave: Se registraron 10 géneros y 27 morfoespecies de HMA. La abundancia varió de 55 a 198 esporas en 100 g de suelo. Ambispora reticulata fue un nuevo registro para Chiapas y México. Acaulospora fue el género más frecuente y rico en morfoespecies. Chiquihuites destacó por tener más riqueza, diversidad y equitatividad de morfoespecies de HMA, explicadas principalmente por los bajos niveles de materia orgánica y PO4-3 en el suelo. En las otras plantaciones la riqueza y diversidad de HMA dependió de la acidez como controlador del PO4-3 disponible en el suelo. Coffea arabica presentó similar riqueza y distinta composición de HMA que C. canephora, comparado con un estudio previo realizado en C. canephora. Conclusiones: Coffea arabica favorece la riqueza de HMA en comparación con C. canephora. La disponibilidad del PO4-3 y la acidez del suelo podrían regular la diversidad de los HMA en C. arabica, así como favorecer la presencia de HMA específicos en estas condiciones edáficas. Las especies de Acaulospora y los géneros sólo registrados en C. arabica podrían conformar biofertilizantes para su cultivo en el Soconusco, Chiapas, México. Palabras clave: acidez edáfica, Ambispora reticulata, cafeticultura, Glomeromycota, micorriza arbuscular, región del Soconusco.