Herbarium-based studies on taxonomy, biogeography and ecology of Psilochilus (Orchidaceae)

BACKGROUND Psilochilus is a poorly studied orchid genus distributed from southern Mexico to south-eastern Brazil. A taxonomic revision of this Neotropical endemic based on morphological data is presented. MATERIAL AND METHODS Over 170 dried herbarium specimens and flowers preserved in liquid of Psilochilus were analyzed. Morphological variation among examined taxa was described based on multivariate analysis. To evaluate the similarity between niches occupied by various Psilochilus species ecological niche modeling (ENM) was applied. Species richness and the distribution patterns of Psilochilus representatives were analyzed based on squares of 5° latitude and longitude while similarities among floras between biogeographical units were measured using the Bray-Curtis index for presence/absence data. RESULTS AND DISCUSSION A new species of the P. physurifolius-complex is described based on Central American material. Psilochilus crenatifolius is reduced to the rank of variety as P. macrophyllus var. crenatifolius. A key to 18 accepted Psilochilus species is provided. The illustrations of perianth segments of all recognized taxa are presented. The climatic niches preferred by the particular Psilochilus representatives are well separated based on ecological niche modeling analysis. Their distribution is limited mainly by the isothermality and temperature seasonality. The highest Psilochilus species richness is observed in the North Andean, Panamanian, Brazilian Planalto and Central American biogeographical provinces. A high level of endemism is observed in all those regions as well as Yungas biogeographical province. Most Psilochilus species occur in areas above 800 m of elevation. The populations were most often reported from the tropical rain forest and tropical moist deciduous forest.