Orchidaceae in floodplains of the islands of Abaetetuba, Amazonian Brazil: a flora threatened by intensive management for açaí palm (Euterpe oleracea)

Amazonia occupies approximately 60% of Brazil and hosts one-third of the country’s orchids. Pará state contains a significant portion of the Brazilian Amazon, the orchidological flora of which has become better documented in the last few decades. The municipality of Abaetetuba comprises several islands predominated by floodplain forest of ombrophilous broadleaf species interspersed with palm trees, especially the açaí palm known as “açaizeiro” (Euterpe oleracea). The species is of great importance to the riverside population and local economy since açaí is the main cultivated product of vegetal origin in the Amazonian estuaries. The opening of new areas for planting and intensive management of “açaizeiro” have a direct influence on local floristic diversity, with subsequent impacts on the epiphytic synusia. This work reports the results of a floristic-taxonomic study of Orchidaceae in floodplain areas of the islands of the municipality of Abaetetuba, Pará, Brazil. A total of 26 species were recorded. Seven species represent new occurrences for the municipality: Christensonella uncata, Eulophia alta, Lockhartia lunifera, Notylia aromatica, Oeceoclades maculata, Pleurothallis pruinosa and Scaphyglottis reflexa. Epiphytic and hemiepiphytic species (92.3%) prevailed over terrestrial species. Most of the holoepiphytes were collected on large trees with rough bark and of commercial interest, such as Hevea brasiliensis (“seringueira”) and Mangifera indica (“mangueira”). Only two species (Catasetum macrocarpum and Vanilla mexicana) were observed on açaí palms, which have a smooth stipe and an unbranched canopy, morphological characteristics we identify as being not favorable for the establishment of epiphytes. Some holoepiphytic species may be threatened locally. We emphasize the need for studies aimed at understanding the effects of intensive açaí palm management on the regional orchid flora.