Presence of the orchid Oncidium maduroi (Orchidaceae: Oncidiinae) in Costa Rica.

the province of Bocas del Toro, Panama, Oncidium maduroi Dressler is here reported for the first time from Costa Rica, based on the following collection: Alajuela: San Carlos, road to the Río La Vieja, along a path at the right of the road about 4 km before the river, 1 000 m, collected by C. Cambronero Araya in 1995, flowered in cultivation, 7 October 2000, F. Pupulin 2437 (USJ, SEL). In Costa Rica this species inhabits premontane forests along the northern Caribbean watershed at about 1 000 m elevation, where it has been found as epiphyte on large branches and trunks in partial shade. It flowers in September and October. Oncidium maduroi is closely related to O. fuscatum Rchb.f., a rather peculiar species originally described under Miltonia Lindl. (Reichenbach 1856) and for which generic placements in Odontoglossum Kunth and Chameleorchis Senghas and Luckel were subsequently proposed (Anonymous 1870, Senghas 1997). For its large and papery floral bracts O. maduroi resembles O. bracteatum Warsz. and Rchb.f., but the latter has ovoid, usually 2-foliate pseudobulbs, longer inflorescences, mostly reflexed sepals, and yellow lip with a much narrower isthmus. Oncidium dichromatichum Rchb.f. presents in Costa Rica a rather frequent rose form (var. rosea Hort.) with a large, solid, reddish brown blotch on the lip comparable to that of O. maduroi, but the former species has long, branched inflorescences and its distribution is restricted to the Pacific slopes of Costa Rican chains. For its flat, rounded and spreading flowers, the relatively compact size and the strikingly pale rose lip, O. maduroi is one of the showiest Oncidium species in Costa Rica. In the original description O. maduroi was depicted with a color photograph of the flower (Dressler 2000), and a botanical illustration of the species is provided here for the first time based on a Costa Rica specimen (Fig. 1).