Plant Ecology and Evolution 149(2): 189-198, doi: 10.5091/plecevo.2016.1150
Circular distribution of three species of epiphytic orchids in shade coffee plantations, in Soconusco, Chiapas, Mexico
expand article infoAlfredo García-González, Anne Damon, Frander B. Riverón-Giró, Irene Ávila-Díaz
Open Access
Background and aims – Cardinal orientation of individuals is one of the least known and understood ecological or demographic factor governing the dynamics of epiphytic orchid populations. The circular distribution of three epiphytic orchids, Oncidium poikilostalix, Oncidium guatemalenoides and Lepanthes acuminata, was studied in shaded coffee plantations in the region of Soconusco, Chiapas, Mexico. A preference for a certain cardinal orientation on the phorophytes was analyzed, using circular statistics.
Methods – Circular distribution tendencies were compared between the three species, two life stages (immatures and adults), and between the microsites (trunk, branch forks, branches, twigs) in which the individual orchids were distributed on the phorophytes.
ResultsOncidium poikilostalix was the most abundant species (1,056 individuals). The three orchid species were found growing mainly on twigs of the coffee bushes. For populations in general, and for the life stages and microsites in particular, individuals of O. poikilostalix and O. guatemalenoides showed a preference for occupying the combination of the cardinal orientations south-southwest-west. Individuals of L. acuminata were orientated towards all eight cardinal points, with a slight numerical preference for east.
Conclusions – Cardinal orientation of orchid species can be driven by specific climatic or ecological factors (e.g. direction and speed of prevailing winds; O. poikilostalix and O. guatemalenoides ). These species may show clearer preferences for growing facing certain cardinal orientations. However, many species can be affected by a combination of microclimatic and ecological factors (e.g. humidity in the microenvironments, proximity to water sources, insolation, shade, competition or wind speed and direction; L. acuminata ), which may influence at such a limited and local scale that orientation patterns may be difficult to detect.