Abstract

In this work, we determined the distribution and relative abundance of terrestrial orchids of the genusBletia 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 roezliiwas 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, theamount and morphotype of the mycorrhizal fungus, which is associated with their dispersibility of them, among other factors.

Key words: Orchid distribution, relative abundance, disturbance.