Context – Oncidium poikilostalix (Kraenzl.) M.W.Chase & N.H.Williams (Orchidaceae) was first reported in Mexico in 2008 and grows on coffee bushes in shaded plantations in Soconusco region in southeast Mexico. Goal – To study the reproductive characteristics and the endophytic fungi with which this orchid is associated to evaluate current conservation status, its possible influence on other epiphytic orchids sharing the same coffee agroecosystem and identify the morphological and adaptive response that have permitted successful colonization of this human landscape. Methods – We determined flower production and percent fruit set, percent loss of seeds due to mechanical or biological damage and total seed rain in two populations, during two years (2008–2009). We characterized morphologically the seed of O. poikilostalix and isolated the fungi associated with its roots. Results – Rapid growth and development of the populations were observed at various levels: recruitment and survival levels were high, with many more adult plants and flowers found in both populations in the second year. Combined percent pollination rose from 1.82% in 2008 to 3.37% in 2009, resulting in the production of 3,387,468 seeds in 2008, rising to 10,001,096 in 2009. We isolated and identified to genus level, thirteen taxa of fungi, including various strains of Rhizoctonia sp. Conclusions – O. poikilostalix interacts with a variety of mycorrhizal symbionts in new habitats. O. poikilostalix is a vigorous and weedy species which should be monitored to prevent it from displacing native, rare and slower growing species, such as Oncidium guatemalenoides M.W.Chase & N.H.Williams, growing in coffee plantations in southeast México.

COFFEE PLANTATIONS; FLOWERING; FRUIT SET; INVASIVE SPECIES; MYCORRHIZAL FUNGI; ONCIDIUM POIKILOSTALIX; ORCHIDACEAE; POLLINATION; REPRODUCTION; SEED RAIN