Synopsis of Orchidaceae from Fazenda Sete Irmãos: a fragment of Amazon Forest in northwestern Maranhão, Brazil

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.


Introduction
Orchidaceae Juss. is widely known as one of the most species-rich plant families (Dressler 1981;Chase et al. 2015). It is especially diverse in the Neotropical region where Brazil stands out with about 220 genera and 2,500 species recorded, of which about 65% are endemic (BFG 2015(BFG , 2018. In northeastern Brazil inventories of Orchidaceae species have been conducted in areas of the states of Bahia (Bastos & Van den Berg 2012;Marinho & Azevedo 2014;Vieira et al. 2014), Maranhão (Silva et al. 1999;Oliveira et al. 2021), Paraíba (Almeida et al. 2007;Moreira et al. 2020), Pernambuco (Pessoa & Alves 2012 and Sergipe (Pessoa & Alves 2011;Monteiro et al. 2012). However, knowledge of the eastern portion of the Amazon forest located in the state of Maranhão is fairly low.
Some recent studies have pointed out new records of Orchidaceae for the state (Ferreira et al. 2017(Ferreira et al. , 2019cGomes et al. 2021;Oliveira et al. 2021), indicating that it is still in need of further taxonomic studies, yet it remains neglected by the majority of Brazilian botanists. Currently 115 species and 49 genera of the family are cited to Maranhão (BFG 2015(BFG , 2018, however a large portion of its area remains fairly poorly collected, especially the northwest region where it includes part of the Belém Endemism Center, one of the most threatened portions of the Brazilian Amazon (Almeida & Vieira 2010).
Thus, this study aims to provide a synopsis of the Orchidaceae species from a fragment of Amazon Forest located in the northwest part of the state. In addition to the inventory, we provide an identification key, photographs of the new records, taxonomic and ecological comments, as well as the geographic distribution of each species. This study will contribute to expanding the knowledge of the orchid flora along the eastern border of the Amazon domain.

Material and Methods
The state of Maranhão, with an area of 331,983 km², presents vegetation with ecotonal features since it is located in a transition zone among the Amazon Forest, the Cerrado and the Caatinga (Muniz 2006). The northwest portion of the state in dominated by ombrophilous and semideciduous forests, while savannahs and palm rich ecosystems locally called "mata dos cocais" are more common in the south and east portions (Abreu 1949;Froés 1953;Ribeiro 1971;Muniz 2004;Almeida & Vieira 2010;Celentano et al. 2017;Silva et al. 2017;Silva-Moraes et al. 2019). The study area is in the northwest part of the state, in the municipality of Cândido Mendes, on a private property called Fazenda Sete Irmãos (01º51'37"S, 45º46'10"W) (Fig. 1). The area includes a fragment of about 7,000 ha of Amazon Forest (Almeida & Vieira 2010), considered one of the largest of the state (Koch & Araújo-Silva 2014;Celentano et  Rodriguésia 73: e02172020. 2022 al. 2017). According to Köppen the climate type is "Am" (Alvares et al. 2013) with mean temperatures between 26-27 °C and annual precipitation between 2,300-2,500 mm (NuGeo 2016).
Field expeditions were conducted monthly between August 2017 and February 2020. The fertile specimens were processed following standard procedures (Fidalgo & Bononi 1984) and deposited at SLUI (Thiers, continuously updated). Sterile specimens were kept under cultivation, awaiting flowering. Taxonomic identification was based upon the specialized literature (Pabst & Dungs 1975, 1977Batista et al. 2008;Pessoa & Alves 2011Koch et al. 2018;Klein & Piedade 2019) in addition to an analysis of type specimens when available on-line. The circumscription of the genera follows the Flora do Brasil 2020 (continuously updated).
The morphological terminology follows Harris & Harris (2001), the data on geographical distribution of the species follow Flora do Brasil 2020 (continuously updated) and Govaerts et al. (2020). The map was produced using QGis ® 2.18.12 Essen (QGIS Development Team 2020) under SIRGAS 2000 datum.

Results and Discussion
Orchidaceae is represented in the study area by 51 species distributed in 24 genera. Epiphytes represent 86% of the species (34 spp.), the remaining are terricolous (6%, 3 spp.), hemiepiphytic (6%, 3 spp.), or myco-heterotrophic (2%, one sp.) (Tab. 1;. The predominance of epiphytes can be explained by the dense canopy observed in the area which does not allow much light to reach the soil. This result agrees with Dressler (1993) who argued that at least 2/3 of the orchid species in the tropics are epiphytes. Epidendrum L. with six species (12%) and Maxillaria Ruiz & Pav. with five species (10%) are the most representative genera in the area. These genera have also been found to be representative in other studies conducted in the Amazon domain (Silveira et al. 1995;Koch et al. 2018;Klein & Piedade 2019).
According to BFG (2015BFG ( , 2018 Among the species 30% are widespread in the Neotropics, while 47% are endemic to South America, and only 6% are restricted to Brazil (BFG 2015(BFG , 2018Govaerts et al. 2020). The majority of the species (about 75%) were collected along rivers or water courses, these areas work as corridors for epiphytes linking the Cerrado and the Amazon (Pabst & Dungs 1975). In the anthropized portion of the Fazenda Sete Irmãos only three species were observed, Catasetum macrocarpum Rich. ex Kunth. and Vanilla palmarum Lindl. growing in Attalea speciosa Mart. (Arecaceae, locally called "Babaçu") and Sacoila lanceolata (Aubl.) Garay a terricolous species.
The Fazenda Sete Irmãos is one of the last wellpreserved localities of Amazon Forest in Maranhão, at least 3,000 ha are primary forest. Our results indicate it is one of the richest areas in Orchidaceae species in northeastern Brazil (Coelho & Amorim 2014; and it is fundamental for conservation of the Belém Endemism Center (Almeida & Vieira 2010;Celentano et al. 2017).
The new records of species presented here are just part of several other studies recently undertaken in the Amazon portion of Maranhão that are also expanding distributions of taxa of other families (Guarçoni et al. 2018(Guarçoni et al. , 2020Ferreira et al. 2019aFerreira et al. , 2019bFerreira et al. , 2019cSilva et al. 2016;Koch & Araújo Silva 2014;Scatigna et al. 2019;Silva-Júnior et al. 2020). We highlight the need for a stronger effort of studying this neglected and threatened region of Brazil. Widespread in northern South America, in Brazil it is widely distributed in the Amazon domain, but it is also recorded to Cerrado. It is a species that while sterile can be confused in the area with O. baueri and B. caudata but in flower is recognized by the lip adnate to the base of the column and with an erose margin (vs. free and entire). The local flowering period is between November and January.  Widespread in the Neotropical region, in Brazil it is widely distributed in the Amazon domain. This species is easily recognized by its long caudate sepals, the most similar species in the area is A. variegata from which it can be distinguished by having more flowers per inflorescence (5-8 vs. 1-3). The local flowering period is between May and July.  Widespread in northern South America and the Caribbean, in Brazil it is found in the Amazon and Atlantic Forest domains. This species was cited by Silva et al. (1999) to Maranhão, but without a testimony voucher. As it is not listed to the state in BFG (2015BFG ( , 2018, here its presence is confirmed. It is easily distinguished from the other species of the genus in the area by the presence of leaves (vs. leafless). The local flowering period is between June and July. Widespread in the Neotropical region, in Brazil it is found in the Amazon and Atlantic Forest domains. This study presents its first record to Maranhão. It is easily recognized among the species of the area by being leafless and by the flat, green roots. The local flowering period is between June and August. Widespread in northern South America, in Brazil it is cited only to the states of Amazonas, Pará and Rondônia. This species was cited by Silva et al. (1999) to Maranhão, but without a testimony voucher. As it is not listed to the state in BFG (2015BFG ( , 2018, here its presence is confirmed. It can be confused in the area with a member of Epidendrum due to the cespitose habit and leaves distributed along the stem, but it differs by membranous leaves and 1-flowered inflorescences (vs. coriaceous, multiflorous). The local flowering period is between June and July. Widespread in the Neotropical region, in Brazil it is found in the Amazon and Atlantic Forest domains. It is a species that can be confused in the area with Epidendrum, but is distinguished by the column adnate only at base with the lip (vs. fully adnate). The local flowering period is between May and July. Widespread in northern South America, in Brazil it is widely distributed, except in the South region. Among the Epidendrum species of the area it can be confused with E. purpurascens due to the deeply 3-lobed white lip, but in E. carpophorum the stem is not swollen (vs. swollen). The local flowering period is between February and August. Widespread in northern South America, in Brazil it is found in the Amazon and Atlantic Forest domains. It is distinguished from the other species of the genus in the area by its long inflorescence and red flowers. The local flowering period is between July and September. Widespread in the Neotropical region, it is also widely distributed in Brazil. It can be confused with E. strobiliferum but the stem of this epiphyte is not branched and the flowers are green (vs. branched, white). The local flowering period is between March and Abril. Widespread in the Neotropical region, it is also widely distributed in Brazil. Among the Epidendrum species of the area it is the only one with ramified, pendent stems. The local flowering period is between May and July.

Widespread in the Neotropical region, in
Brazil it is widely distributed, except in the South region. This twig epiphyte with equitant leaves can be confused in the area, if sterile, with a member of Ornithocephalus, but the flowers are fairly distinctive, and it can be recognized by the color (yellow vs. white or greenish), margin of the petals (entire vs. minutely denticulate), and the presence of wings on the column (vs. without wings). The local flowering period is between June and August. Distributed in Guyana, Suriname and Brazil, where it is found in the Amazon and Atlantic Forest domains, it has been cited only to the states of Amazonas, Maranhão, Pará and Pernambuco. It is similar to G. quinquenervis but differs by the perianth length (4-5 cm long vs. 2.5-4 cm long). The local flowering period is between October and November. Distributed in Colombia, Ecuador, Peru and Brazil, where it is found in the Amazon and Atlantic Forest domains. As mentioned above, it is similar to G. nigrita, but can also be distinguished by the length of lip callus (< 0.1 cm long vs. > 0.2 cm long). The local flowering period is between October and November.  Widespread in northern South America, in Brazil it is widely distributed. This species was cited by Silva et al. (1999) to Maranhão, but without a testimony voucher. As it is not listed to the state in BFG (2015BFG ( , 2018, here its presence is confirmed. Among the species of the area, young individuals of this species can be confused with E. purpurascens due to the heteroblastic fusiform pseudobulbs, but these species are easily distinguished by the length of the peduncle (> 20 cm long vs. < 8 cm long) and color of the flowers (sepals and petals brown, lip pale pink vs. completely white). The local flowering period is between April and May. Widespread in northern South America, in Brazil it is widely distributed in the Amazon domain. This study presents its first record to Maranhão and also to northeastern Brazil. Among the twig epiphytes with unifacial leaves of the area, it is the only one with an elongated stem. The local flowering period is between May and July. Widespread in northern South America, the species has also been recorded to Belize, in Brazil it is widely distributed in the Amazon and Cerrado domains. This twig epiphyte is the only one among the species with unifacial leaves that produces pink flowers with a clawed lip. The local flowering period is between October and December. Widespread in the Neotropical region, in Brazil it is widely distributed in the Amazon and Cerrado domains. It can be confused in the area with M. lutescens due to the pendent habit, but differs by having 1 apical leaf (vs. 2) and vestigial lateral lobes of the lip (vs. developed). The local flowering period is between May and June. Christenson, Orchids (West Palm Beach) 71: 125 (2002). Widespread in the Neotropical region, and also in Brazil. It is similar to M. alba, but the leaves are wider (up to 2.5 cm wider vs. < 1 cm wider), other features used to distinguish these two species are in the comments of M. alba. The local flowering period is between January and April.

Widespread in northern South America, in
Brazil it is widely distributed in the Amazon and Atlantic Forest domains. It is easily distinguished among the other Maxillaria of the area by its longer peduncle (> 6.5 cm long vs. < 2.0 cm long) and shorter lip (< 0.6 cm long vs. > 1.0 cm long). This species was formerly included under Trigonidium, considered part of Maxillaria s.l. today. The local flowering period is between June and November. Lindl. Edwards's Bot. Reg., 23: t. 1986, 1837.  Distributed in Ecuador, Guyana, Peru, Venezuela and Brazil, where it is cited only to the states of Bahia, Espírito Santo, Mato Grosso, Pará and Pernambuco. This study presents its first record to Maranhão. This species is easily distinguished from the other Notylia of the area by its lateral sepals completely connate (vs. free at distal half) and lip blade ovate (vs. lanceolate). The local flowering period is between November and December. Distributed in Bolivia, Colombia, Ecuador, Peru, and Brazil, where it is widely distributed. Its most similar species in the area is T. egleri, but these species are easily distinguished by the color the flowers (dark purple vs. yellow) and the fusion of the lateral sepals (free vs. connate). The local flowering period is between January and May.  Widespread in northern South America, the species has also been recorded to Costa Rica, in Brazil it is widely distributed in the Amazon and Atlantic Forest domains. This species was cited by Silva et al. (1999) to Maranhão, but without a testimony voucher. As it is not listed to the state in BFG (2015BFG ( , 2018, here its presence is confirmed. Its flowers are somewhat similar to E. pusilla, but the presence of pseudobulbs (vs. absent) and the bi-facial leaves (vs. unifacial) distinguish these two. The local flowering period is between November and April. Barb.Rodr., Genera et Species Orchidearum Novarum, 1, 1877. Examined material: Macaxeira river, 01°52'15. 1"S, 45°47'58.5"W, 20.II.2020, fl., A.W.C. Ferreira 076 (SLUI 5759). Widespread in northern South America, in Brazil it is widely distributed in the Amazon domain. It can be confused in the area with a member of Epidendrum but differs by its column totally free (vs. adnate to the lip claw). The local flowering period is between September and February. Barb. Rodr., Gen. Sp. Orch. Nov. 1:133.1877. Endemic to Brazil where it is cited only to the states of Amazonas, Ceará, Mato Grosso, Pará and Rondônia. This study presents its first record to Maranhão. In the area it is similar to O. gladiatus Hook. but differs by the sepals rounded to obtuse at apex (vs. acuminate) and the lip entire (vs. 3-lobed). The local flowering period is between June and August. Widespread in northern South America, in Brazil it is widely distributed, except in the South and Southeast regions. As mentioned before, it is similar to O. cujeticola; the features used to distinguish them are described in the comment above. The local flowering period is between June and September. Endemic to Brazil, where it is cited only to the states of Pará and Maranhão, in the Amazon domain. It can be confused with C. speciosa due to the heteroblastic pseudobulbs and plicate leaves but is easily distinguished by its smooth pseudobulb (vs. ribbed). The local flowering period is between January and February. (Jacq.) Garay & H.R.Sweet, Orquideología, 9: 206, 1974. Fig. 3c Examined material: trilha para o igarapé Cumaruzal, 01°50'36.6"S, 45°47'09.8"W, 4.V.2018, fl., M.J.C. Silva & A.W.C. Ferreira 082 (SLUI 5765). Widespread in the Neotropical region, in Brazil it is cited only to the states of Amapá, Goiás, Mato Grosso and Rondônia, in the Amazon and Cerrado domains. This species was cited by Silva et al. (1999) to Maranhão, but without a testimony voucher. As it is not listed to the state in BFG (2015BFG ( , 2018, here its presence is confirmed. In the area, the only other species with swollen stems, terminal inflorescence and non-resupinate flowers is P. aemula, but it is easily distinguished by its 3-lobed lip (vs. entire). The local flowering period is between February and May. (Lindl.) W.E.Higgins, Phytologia 82: 376 (1997publ. 1998). Widespread in northern South America, it has also been recorded to Panama, in Brazil it is widely distributed. Young specimens of this species can be confused in the area with E. purpurascens, due to the fusiform heteroblastic pseudobulbs, but it is easily distinguished by the entire lip (vs. 3-lobed). Specimens of P. aemula has been identified as P. fragrans, but this second species is not found in the state. The local flowering period is between October and April. Widespread in northern South America, it has also been recorded to Panama, in Brazil it is widely distributed in the Amazon domain, but is also cited to surrounding Cerrado. Among the species with heteroblastic pseudobulbs, lateral inflorescences and lip not clawed in the area it is the only one with purple flowers and lateral sepals connate. The local flowering period is between January and March. Widespread in northern South America and Central America, in Brazil it is widely distributed. This study presents its first record to Maranhão. As mentioned before, it can be confused with S. lanceolata, but its greenish-white flowers are fairly distinctive for lacking a spur (vs. flowers magenta, spur present). The local flowering period is between August and September. Widespread in the Neotropical region, in Brazil it is widely distributed, except in the South region. This study presents its first record to Maranhão. It is similar to S. stellata but differs by the white to beige flowers (vs. pink) and column without lateral appendixes (vs. with lateral appendixes). The local flowering period is between July and August. Pabst, Orquídea (Rio de Janeiro) 18: 7. 1956. Widespread in northern South America, in Brazil it is found in the Amazon and Atlantic Forest domains. This species differs from the other Scaphyglottis of the area by its sepals connate at base (vs. free) and shorter perianth (< 3.0 mm long vs. > 5.0 mm long). The local flowering period is between May and July. Endemic to Brazil, where it is cited only to the states of Mato Grosso, Pará and Rondônia in the Amazon domain. This study presents its first record to Maranhão and also to northeastern Brazil. It can be confused in the area with S. egleri and O. grandiflora but differs by its lateral and dorsal sepals fused (vs. dorsal sepal free). The local flowering period is between February and April.   Widespread in northern South America, in Brazil it is widely distributed in the Amazon domain. This study presents its first record to Maranhão and also to northeastern Brazil. It can be confused in the area with O. grandiflora and S. paraensis but can be easily recognized by its lepanthiform sheaths. The local flowering period is between January and April.

Vanilla mexicana
Mill., Gard. Dict. ed. 8: n.º 1 (1768). Widespread in the Neotropical region, in Brazil it is also widely distributed, except in the South region. It can be confused in the area with V. palmarum but differs by its sepals and petals undulate at margin, green (vs. flat, yellow). The local flowering period is between July and August. Widespread in northern South America, in Brazil it is widely distributed, except in the South and Southeast regions. In the area it can be confused with V. mexicana but it grows exclusively on palm species (vs. other phorophytes). The local flowering period is between September and January. Widespread in the Neotropical region, in Brazil it is widely distributed, except in the South region. It is easily distinguished from the other species of Vanilla in the area by its lip with a multi-ridged callus on the disc (vs. callus absent). The local flowering period is between August and October. Widespread in the Neotropical region, in Brazil it is widely distributed in the Amazon domain. This study presents its first record to Maranhão and also to northeastern Brazil. It is the only myco-heterotrophic herb in the area, recognized by achlorophyllous stems and scale-like leaves. The plants arise from the soil in the area between March and July, and local flowering period is between October and November.