Abstract In the present study we propose a new Catasetum taxon belonging to the group of species with symmetrical and converging antennae. It was found in a vegetation of “terra firme” and “campinarana” in the central Brazilian Amazon. A detailed description of the taxon is given as well as a photograph plate and comments relating to distribution, habitat, phenology and conservation status. It is compared to C. rivularium and C. barbatum which are sympatric species and somewhat similar to the new taxon. Furthermore, we present a key to Catasetum species with symmetrical and convergent antennae occurring in the Brazilian Amazon. terra firme campinarana “campinarana Amazon distribution habitat status C Furthermore

Resumo Este estudo apresenta um inventário das Orchidaceae em uma das áreas mais ameaçadas da Amazônia Brasileira, localizada na porção mais oriental do Centro de Endemismo Belém. São registradas 51 espécies distribuídas em 24 gêneros. Epífitas representam 86% das espécies, as demais são terrícolas (6%), hemiepífitas (6%) ou micoheterotrófica (2%). Os gêneros mais representativos foram Epidendrum (6 spp.) e Maxillaria (5 spp.). Este estudo registra pela primeira vez cinco gêneros (Coryanthes, Sarcoglottis, Stelis, Trichosalpinx e Wullschlaegelia) e dez espécies para a flora do Maranhão, dos quais, quatro também são novos registros para a Região Nordeste do Brasil. Uma chave de identificação, pranchas fotográficas dos novos registros e comentários taxonômicos, ecológicos e de distribuição geográfica são apresentados. Os dados evidenciam a importância dos fragmentos de Floresta Amazônica do Maranhão para a proteção das Orchidaceae, constantemente ameaçadas pelo desmatamento no Centro de Endemismo Belém.

Abstract This study provides an inventory of the Orchidaceae in one of the most threatened areas of the Brazilian Amazon, situated in the eastern portion of the Belém Endemism Center. A total of 51 species, distributed in 24 genera, are recorded. Epiphytes represent 86% of the species, the remaining are terricolous (6%), hemiepiphytic (6%) or myco-heterotrophic (2%). The most representative genera were Epidendrum (6 spp.) and Maxillaria (5 spp.). This study cites for the first time five genera (Coryanthes, Sarcoglottis, Stelis, Trichosalpinx and Wullschlaegelia) and ten species for the flora of Maranhão, of which four are new records to the Brazilian Northeast. An identification key, photographs of the new records, taxonomic and ecological comments, as well as geographic distribution are provided. The data reinforce the importance of the forest fragments of the Amazon Forest in Maranhão for the conservation of Orchidaceae which is constantly threatened by deforestation in the Belém Endemism Center.

ABSTRACT An updated checklist of the Orchidaceae from the state of Maranhão is provided. We confirmed 51 genera and 119 species, of which the most representative genera are Habenaria (17 spp.), Catasetum (14 spp.) and Epidendrum (10 spp.). Our checklist includes 30 species that are not listed in the Flora do Brasil for the state, many of which, however, have been recorded in previous publications. Thus, excluding these, six species are cited here for the first time to Maranhão, all of which are also new records for the Brazilian Northeast region. Comparing such data with previous lists, with 103 and 105 species, we detected a strong incongruity among the data. Of the former list, 25 species lack vouchers from the state and were not collected in our expeditions, thus these taxa are not confirmed, while of the latter we found 20 species that are also not confirmed for the same reasons. A list with the 34 excluded taxa is provided. Most of the collection effort in the state coincides with university campuses, and the northwestern region is the most species rich, but unfortunately it is also the most threatened area.

Resumo A região leste do estado do Maranhão é uma área de transição entre a Amazônia, Cerrado e a Caatinga. Pouco se conhece sobre a flora dessa região, especialmente com relação à Orchidaceae. O objetivo desse estudo foi realizar o levantamento das espécies desta família na área central desta região. As coletas em campo foram realizadas mensalmente entre dezembro de 2015 e abril de 2019 nos municípios de Aldeias Altas, Caxias, Codó e São João do Sóter. São apresentadas uma chave de identificação, descrições morfológicas e imagens das espécies encontradas. Orchidaceae está representada na área por sete gêneros e 17 espécies. Os gêneros mais ricos foram Catasetum (cinco espécies), Habenaria (quatro espécies). Habenaria schenckii é um novo registro para a Flora do Maranhão. A maioria das espécies apresentou hábito epífitico (oito espécies, 47%) ou terrícola (sete espécies, 41%). O município de Caxias foi o mais rico, com 13 espécies (76%), sendo seis destas coletadas nas Áreas de Proteção Ambiental (APAs) existentes no município (APA Municipal do Buriti do Meio e a APA Municipal do Inhamum). Os dados evidenciam a importância das Unidades de Conservação para a proteção das Orchidaceae, e o potencial das regiões ecotonais na descoberta de novos registros.

Abstract The eastern portion of the state of Maranhão is a transitional area between Amazon Rainforest, Cerrado and Caatinga. Knowledge about the flora of this region is very poor, especially regarding Orchidaceae. The aim of this study was to provide a survey of the species of this family in the central area of this region. Fieldwork was performed monthly between December 2015 and April 2019 in the municipalities of Aldeias Altas, Caxias, Codó and São João do Sóter. An identification key, morphological descriptions and illustrations of the species are presented. Orchidaceae is represented in the area by seven genera and 17 species. The richest genera were Catasetum (five species), and Habenaria (four species). Habenaria schenckii is a new record for the state. The majority of the species are epiphytes (eight species, 47%) or terrestrial (seven species, 41%). The municipality of Caxias was the richest, with 13 species (76%), of which six were collected in the conservation units (CU’s) existing in the municipality (Área de Proteção Ambiental Municipal (APAM) Buriti do Meio Municipal and APAM Inhamum). Our data highlight the importance of the CU’s for the conservation of Orchidaceae, and the potential of ecotonal regions for discovering new records for the region.