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Background: Epiphyte removal forms part of routine management in shade coffee plantations. Aims: Assess the current status of three population orchids growing in Mexican shaded coffee plantations and evaluate the effect of perturbing the transient behaviour of different life stages. Methods: We modelled the short-term response of eliminating I) non-reproductive juveniles, or II) reproductive adult plants from coffee bushes, on populations of Oncidium poikilostalix, Lepanthes acuminata and Telipogon helleri (Orchidaceae). First, we calculated the transient dynamics per se and second, we made a perturbation analysis on population inertia. Finally, we made a comparison with a traditional sensitivity analysis. Results: All three species showed different positive asymptotic growth rate: O. poikilostalix (λmax = 1.106), L. acuminata (λmax = 1.209), and T. helleri (λmax = 1.012). The effect of eliminating the major part of the juvenile or adult orchids gave population inertia in relation to steady state, respectively, (+19%, -24%) for O. poikilostalix, (+17%, -28%) for T. helleri and (+57%, -35%) for L. acuminata. Conclusions: Eliminating juveniles or adults affects in different ways the short-term dynamics due to differential impact on size stages that have the non-linear effects associated with important disturbances that currently affect orchids growing in coffee plantations. [ABSTRACT FROM AUTHOR]

Background: Understanding the effect of perturbation, be it natural or anthropogenic, on the demography and dynamics of the plant populations can help conservation management planning. Aims: We assessed the impacts of management of a shade coffee plantation on a population ofOncidium poikilostalix(Orchidaceae). Methods: We studied in a coffee (Coffea arabica) agroecosystem the impact of the current traditional management [T] and two hypothetical epiphyte control management scenarios (intense ‘desmusgue’ [ID] and moderate ‘desmusgue’ [MD]), on the only known Mexican population ofO.poikilostalix. Based on 3 years of field demographics data, the population dynamics of the orchid were projected using T, ID and MD scenarios for 20 years into the future. Results: Under the current management T, the population ofO. poikilostalixwas projected to grow continuously (λ = 1.102). Conversely, under management ID, the loss of individuals would lead to a sustained population decline (λ = 0.843); in the case of MD, the population would decline more slowly with the population growth rate tending towards equilibrium (λ = 0.966). Conclusions: The changes in the management of coffee plantations that have become common throughout the south-east of Mexico represent a threat to the survival of the only population ofO. poikilostalixin Mexico, and likely threaten other epiphytic species. [ABSTRACT FROM PUBLISHER]

Oeceoclades maculata is the most successful invasive orchid in the Neotropics. The anatomy of the vegetative organs, peduncle and seeds of O. maculata was characterized to identify features of possible physiological and ecological importance. Plants from four locations in Soconusco, Chiapas, Mexico were selected. Transverse, longitudinal and paradermal sections of vegetative organs were observed using light and scanning electron microscopes. Oeceoclades maculata has amphistomatous leaves, with smooth and a thin to slightly thickened cuticle, a single-layered epidermis, a low density of small stomata (<13 mm-2) and numerous sunken glandular hairs on both surfaces. Mesophyll is homogeneous with abundant extravascular fibre bundles. The root has a multilayered velamen with abundant tilosomes. Numerous idioblasts with raphides were observed in leaves, pseudobulbs and roots. The seeds are fusiform, with smooth surfaces and transverse folds. Some of these traits link O. maculata with terrestrial and epiphytic habits and with xerophytic habits, with humid and high light intensity and humid environments. This combination of traits might be a key factor behind the success and expansion of O. maculata. Nonetheless, a detailed characterization of the microhabitats occupied, demography, reproductive strategies and mycorrhizal associations will be essential for understanding the behaviour of this invasive species and, if necessary, designing strategies for its control. [ABSTRACT FROM AUTHOR]