Investigacion en orquideas

AUTORES:
1) El Dr. Octavio Reyes López es Profesor de Tiempo Completo en la Dirección de Investigación y Postgrado de la Universidad Virtual del Estado de Guanajuato (UVEG). (autor de correspondencia). Su correo electrónico es: ocreyes@uveg.edu.mx
2) El Dr. Rafael Espinoza Mosqueda es Profesor de Tiempo Completo en la. División de Ciencias Sociales y Administrativas de la Universidad de Guanajuato, Campus Celaya-Salvatierra.
3) El Dr. Ramón Olvera Mejía es Coordinador del Centro de Estudios Estratégicos [CEDE] de la Universidad Latina de México y Catedrático Invitado del Postgrado en diversas instituciones educativas.


RESUMEN:
El presente reporte, corresponde a una investigación cualitativa de tipo longitudinal que ha sido piloteada tres años, en donde se adoptó el diseño de Teoría Fundamentada y se utilizó la metodología EMFIS, este trabajo fue desarrollado con el objetivo de apoyar las investigaciones del postgrado en la determinación, argumentación y validación del tamaño de muestra en estudios descriptivos. Para tal fin se abordan diferentes planteamientos para que el investigador justifique de manera correcta y en forma apropiada la determinación del tamaño y la representatividad de la muestra seleccionada, dependiendo de la naturaleza de los datos disponibles y/o del propósito del proyecto de investigación.

Los criterios para la determinación del tamaño de muestra, serán diferentes en caso de tratarse de una investigación cualitativa a diferencia de trabajar con énfasis cuantitativo, incluso éste último dependerá del propósito del proyecto por si requiere la estimación de medias o de proporciones y si el valor de "N" es indeterminado o conocido; por otra parte los criterios para la determinación de "n" como tamaño de muestra variarán en el caso de ensayar con pruebas piloto, o tratándose de comunidades muy dispersas, así también cuando se busca muestrear cada localidad en un amplio universo de estudio.

Palabras clave: Tamaño y representatividad de la muestra. Estudios descriptivos.

In this work, we determined the distribution and relative abundance of terrestrial orchids of the genus Bletia in the Cupatitzio Natural Reserve, Michoacán, México, during two flowering seasons. Four different sampling sites were identified according to degree of disturbance and site quality. Relative abundance was established with an arbitrary scale of four values: abundant (>40 individuals), medium (20 to 40 individuals), low (<20 individuals) and null. Three species of orchids were found: Bletia roezlii was the most abundant, with populations of over 40 specimens per 1000 m2 in some sites (zones 1 and 3). It was present in all the reserve’s sites, although it showed better development in areas near roads and/or in open sites. Bletia purpurata had medium distribution and abundance, with more of 30 plants per site, having more presence in conserves sites (zone 3). Bletia punctata had the lowest abundance and distribution, with populations of 10 or less individuals, presenting a mean abundance of low disturbance sites. The distribution of the specimens of Bletia spp. is determined by factors such as the degree of disturbance of the sites where they develop, the adaptability of the species, the amount and morphotype of the mycorrhizal fungus, which is associated with their dispersibility of them, among other factors.

Symbiotic seed germination is a critical stage in orchid life histories. Natural selection may act to favor plants that efficiently use mycorrhizal fungi. However, the necessary conditions for natural selection – variation, heritability, and differences in fitness – have not been demonstrated for either orchid or fungus. With the epiphytic orchid Tolumnia variegata as a model system, we ask the following questions: (1) Do seeds from different individuals in a population differ in germination and seedling development in the presence of the same fungi? (2) Do different mycorrhizal fungi (Ceratobasidium spp.) differ in ability to stimulate seed germination and growth in T. variegata? And (3) are the Ceratobasidium isolates that best induce seed germination and seedling development more closely related to each other than to isolates that are less effective? We performed symbiotic seed germination experiments in vitro. The experiments were done using mycorrhizal fungi isolated from T. variegata; relationships among the fungi were inferred from nuclear ribosomal ITS sequences. We found significant variation for both symbiotic germination and seedling growth among biparental seed crops obtained from a population of T. variegata plants. Differences among Ceratobasidium fungi in seed germination were significant. The fungi that induced highest seed germination and seedling development belonged to two of four clades of Ceratobasidium. The two experiments show that there is potential for natural selection to act on orchid–fungus relationships. Given that orchids vary in performance, and that mycorrhizal fungi are not geographically distributed homogeneously, mycorrhizae may affect population size, distribution and evolution of orchids