Oncidiinae ( Orchidaceae ) on the great curve of the Xingu River , Pará state , Brazil

Among the studies on Orchidaceae in the Amazon, none comprised the region of the Great Curve of the Xingu River, located in the lower Xingu river. The aim of this study was to inventory and taxonomically study the species of Oncidiinae (Orchidaceae) in the Great Curve of the Xingu River, Pará state. The floristic survey was performed in the area of the Belo Monte hydroelectric plant, in the Vitória do Xingu municipality, centrally inserted in the called Great Curve of the Xingu River. Botanical collections were accomplished between June 2011 and December 2013. A total of 27 species of Oncidiinae, distributed in 15 genera, was inventoried in the study area. Notylia Lindl. and Trichocentrum Poepp. & Endl. were the richest genera, with five and four species, respectively, followed by Erycina Lindl., Ionopsis Kunth, Lockhartia Hook., Macradenia R.Br., and Ornithocephalus Hook., with two species each. The remaining eight genera are represented by a single species each in the study area. Morphological descriptions, a key for taxonomic identification, illustrations, and comments on distribution, ecology, phenology and morphology are provided for all inventoried species.


Introduction
The Oncidiinae (Orchidaceae, Epidendroideae, Cymbidieae) includes more than 1600 species in 61 genera and is one of the most diverse subtribes of the Orchidaceae (Dressler, 1993;Chase et al., 2003).This heterogeneous group has a broad morphological diversity of floral and vegetative structures (Chase et al., 2003;Neubig et al., 2012) and the widest range of chromosomes numbers known for Orchidaceae, with a noticeable variation in genome size (Chase et al., 2005;Neubig et al., 2012).The species inhabit different environments and, hence, have a great diversification of pollination systems (Dressler, 1993;Papadopulos et al., 2013).Neotropical forests are usually rich in Oncidiineae species, which grow from the sea level to almost 4000 m.s.m, in the Andean mountain chain (Dressler, 1993;Chase et al., 2003;Neubig et al., 2012).
Typically, Oncidiinae species are epiphytes, although some can be terrestrial or rupiculous (Dressler, 1993;Chase et al., 2003); leaves are distichous, conduplicate and/or equitant, articulate or not, cylindrical or laterally compressed; inflorescences are lateral, simple or branched, with one to several flowers.The flowers can be ressupinate or not; labellum can present a menthum or calcar, and usually have a callus of several distinct shapes.In general, lateral inflorescence, the presence of a conspicuous callus in the labellum, and two cartilaginous pollinia with a short viscidium and long stipe are distinguishing features of the Oncidiinae (Dressler, 1993).
Floristic surveys of Orchidaceae performed in Pará state revealed Oncidiinae as one of the richest subtribes, as in results of Cardoso et al. (1995), Medeiros and Jardim (2011), Silveira et al. (1995), von Atzingen et al. (1996) and Koch et al. (2014).Although a detailed inventory of the Orchidaceae in the Great Curve of Xingu River region has never been accomplished, Ilkiu-Borges and Cardoso (1996) recorded 40 species of Orchidaceae in the called Xingu microregion, a much wider region which encompasses at least part of this study area.
The region known as the Great Curve of Xingu River, is located in the lower Xingu river (Ab'Sáber, 1996).The dominant vegetation types are evergreen lowland dense rainforest, evergreen lowland open rainforest, and open forests dominated by palms, but less than 40% of the original vegetation in the region of the Great Curve of the Xingu River remains preserved (Salomão et al., 2007).At present, the area is under the influence of the construction of Belo Monte hydroelectric plant.
Given the lack of an accurate floristic survey in the region, this work aims to inventory and taxonomically study the species of Oncidiinae (Orchidaceae) in the Great Curve of the Xingu River, Pará state.Morphological descriptions, a key for taxonomic identification, illustrations, and comments on distribution, ecology, phenology and morphology are provided for all inventoried species.

Material and Methods
The floristic survey was performed in the area of the Belo Monte hydroelectric plant (03°22'00"S / 51°56'00"W), in the Vitória do Xingu municipality (Figure 1), centrally inserted in the called Great Curve of the Xingu River (Ab'Sáber, 1996).
The climate is Am, according to Koopen's classification, with average temperature of 26 °C, annual precipitation 2.289 mm and average relative humidity ranging from 78% to 88% (Sousa-Júnior et al., 2006).
Four main types of phytophysiognomies are found in the study area: evergreen dense rainforest, riverine evergreen rainforest, evergreen lowland open rainforest, and open palm dominated forests (Salomão et al., 2007).The vegetation in the region is widely fragmented due to the history of human occupation, based on several types of land use and extractivism (Salomão et al., 2007).
Samples examined in this study were, in part, obtained from the project "Survey and Scientific exploitation of the Flora of the UHE Belo Monte", which is part of the Basic Environment Plan of the Norte Energia S.A. company.The samples were regularly collected from June 2011 to December 2013 by the team of the mentioned project.Additionally, three field expeditions to the study area were done by the first author for further collections, which were herborised according to usual techniques.Additional information for the species, such as phenology, habit, habitat, and photographs were also annotated during the field work.
Sterile specimens were collected and kept until blooming in the greenhouse of the Environmental Studies Centre (CEA) of the Norte Energia S.A. company and, then, herborised.The specimens were deposited in the Herbarium MG, of the Museu Paraense Emílio Goeldi, and flowers were preserved in liquid media (alcohol 70%, water 25% and glycerin 5%).
Morphological terminologies follow Radford et al. (1974), Gonçalves and Lorenzi (2011), and with pertinent literature for Orchidaceae.All information provided in the description was based on the examined specimens.Author names abbreviations are according to Brummitt and Powell (1992).The genus circumscriptions are in accordance with Govaerts et al. (2014).
Illustrative plates were elaborated based on the diagnostic floral charts prepared for the collected specimens.These were digitalised and edited on GIMP 2.8 software.

Results and Discussion
A total of 27 species of Oncidiinae, distributed in 15 genera, was inventoried in the study area.Notylia Lindl.and Trichocentrum Poepp.& Endl.were the richest genera, with five and four species, respectively, followed by Erycina Lindl., Ionopsis Kunth, Lockhartia Hook., Macradenia R.Br., and Ornithocephalus Hook, with two species each.The remaining eight genera are represented by a single species each.2a).
Aspasia variegata is characterised by its ellipsoid, laterally compressed and oblique pseudobulbs, inflorescences shorter than the leaves, with 1-3 flowers, and a patent labellum, which is fused with the column on its half base.
It is endemic to Brazil, known from the states of Amazonas, Maranhão, Pará, Roraima, and Mato Grosso (Silva et al., 1995;Barros et al., 2014).In Pará, it was recorded on the Ilha do Combu (Medeiros and Jardim, 2011).The species is quite common in the study area, occurring in evergreen forest formations, and was observed blooming from March to August.
Brassia chloroleuca is easily recognized among other orchids in the study area by its inflorescences with conspicuous flowers (up to 12 flowers) with narrow sepals, especially the lateral ones, which can reach 14 cm long.
Caluera tavaresii is endemic to Brazil, only known by the type specimen from Oriximiná, state of Pará (Barros et al., 2014;Govaerts et al., 2014).This is, therefore, the second record of this rare species.It was found in forests in regeneration, blooming in June and July.
The species is remarkable by its short size, ensiform leaves, and umbelliform inflorescences, consisting of 4-5 flowers with a cordate labellum.
Erycina glossomystax occurs in Tropical America (Govaerts et al., 2014), from Mexico to Brazil, where it is known for the states of Acre, Amazonas, Pará, Rondônia, Bahia, Maranhão, Espírito Santo, and Rio de Janeiro (Pabst and Dungs, 1977;Barros et al., 2014).In Pará state, it was recorded in Serra dos Carajás (Silveira et al., 1995) and Serra das Andorinhas (von Atzingen et al., 1996).In the study area, E. glossomystax was collected in disturbed areas, usually growing as epiphyte on twigs of shrubs and small trees.It was found with flowers in July, August and October.
Erycina glossomystax is, at first glance, similar to E. pusilla by its typical small size, equitant leaves and few flowered inflorescences, but it can be distinguished by its typically ciliate or deeply denticulate callus in the labellum (vs.callus glabrous and with entire margins in E. pusilla).
Morphological affinities with E. glossomystax were discussed under the latter species.
Ionopsis satyrioides is widely distributed in Tropical America and West Indies, with records for Colombia, Guiana, Panama, Suriname, and Venezuela (Dunsterville and Garay, 1959;Werkhoven, 1986;Govaerts et al., 2014).In Brazil, it occurs in Amazonas, Pará and Maranhão (Silva et al., 1995;Barros et al., 2014) states, with records for Serra dos Carajás (Silveira et al., 1995) and Serra das Andorinhas (von Atzingen et al., 1996) in Pará.It was collected in secondary forests and disturbed areas in the study area, blooming in January, February and October.
Ionopsis satyrioides can be easily distinguished from I. utricularioides by its terete leaves, cylindrical pseudobulbs and inflorescences never longer than 18 cm, with whitish translucent flowers.Ionopsis utricularioides has flat linear-lanceolate leaves, subcylindrical pseudobulbs and inflorescences 40-130 cm long, with flowers pinkish to purplish.
Morphological comparison with I. satyrioides is presented under the latter species.
Lockhartia imbricata is distributed throughout Tropical America, from Mexico to Brazil (Pabst and Dungs, 1977;Werkhoven, 1986;Govaerts et al., 2014).In Brazil, it was recorded in Acre, Amazonas, Amapá, Pará, Rondônia and Mato Grosso (Barros et al., 2014).In the study area, it is a common species and was found growing in evergreen dense forests and secondary vegetation, blooming from May to November.
Lockhartia imbricata can be distinguished of L. lunifera in the study area mainly by the size of lateral lobes of labellum, which are smaller in L. imbricata (4 mm) when compared to L. lunifera (8 mm).
A comparison between Lockhartia lunifera and L. imbricata is provided under the latter species.
Specimens examined: Brazil.Pará: Vitória do Xingu, UHE Belo Monte, Sítio Pimental, 15-01-2013, fl., PSACF 20130115.03E01(MG); Macradenia lutescens is distributed from Southern Florida (United States) to Tropical America (Dunsterville and Garay, 1961;Werkhoven, 1986;Govaerts et al., 2014).The knowledge on the distribution in Brazil not accurate, but it is as far known in the Amazon phytogegraphic domain (Barros et al., 2014).The record in the study area is the first of M. lutescens in Pará state, being found growing in evergreen dense riverine forests, where it is quite rare.The species was found blooming in a greenhouse in July, August, September, October and November.
Although not easily differentiated by vegetative features, the two Macradenia species recorded in the study area (M.lutescens and M. multiflora) can be distinguished from each other by the number and the color of the flowers and the shape of the labellum lateral lobes.Macradenia lutescens has 3-7 flowers, which are yellowish to orange, with petals presenting purple spots, and lateral lobes of the labellum rounded.In turn, M. multiflora has inflorescences with 12-26 flowers, which are purplish with margins greeninsh-yellow, and labellum lateral lobes narrow acuminate.
Occurs in Brazil and Paraguay (Govaerts et al., 2014).In Brazil, it is distributed in the states of Pará, Rondônia, Tocantins, Goiás and Mato Grosso, Minas Gerais, São Paulo and Rio Grande do Sul (Pabst and Dungs, 1977;Barros et al., 2014).It is a common species in the study area, and was found growing in evergreen dense forests and secondary forests, blooming in March, April, May, June, November and December.
Comparative morphological features between both Macradenia in the study area are under the comments provide for M. lutescens.
It can be distinguished among other Oncidiinae species in the study area by its small size, leaves green, equitant, ensiform, and with purple spots, inflorescence a compacted umbelliform raceme, and a long and thin column with curved apex.
Notylia barkeri occurs from México to Northern Brazil (Govaerts et al., 2014), in the states of Amazonas, Pará, Tocantins, Pernambuco, Sergipe and Mato Grosso (Pabst and Dungs, 1977;Barros et al., 2014).In Pará, there are records from Serra dos Carajás (Silveira et al., 1995) and Serra das Andorinhas (von Atzingen et al., 1996).It is quite common in disturbed places and secondary forests in the study area, where it was found blooming in January, March, April, May and June.
This species is characterised by its dense racemose inflorescence with flowers whitish-green, and a cordate labellum.The flowers in N. barkeri are larger than those of N. lyrata (9 mm vs. 7 mm wide), a feature that helps in the recognition of both species in the study area.
Notylia lyrata is found in Paraguay and Brazil (Govaerts et al., 2014), being widespread in the latter country, with records for all regions (Pabst and Dungs, 1977;Barros et al., 2014).In the study area, it was collected in secondary forests, blooming in May.
It differs from N. barkeri by its shorter and wider labellum, and larger flowers, as discussed in the comments of N. barkeri.
Known from Guiana, Venezuela, Brazil, Bolívia, Ecuador and Peru (Dunsterville and Garay, 1965;Govaerts et al., 2014).In Brazil, it was recorded only in Pará state (Medeiros et al., 2009;Medeiros and Jardim, 2011;Barros et al., 2014).It is a common species in the study area, where it blooms in February and March.
Notylia peruviana is the most distinctive species of the genus in the study area.It can be easily recognised by its suborbicular to oblong labellum and non-falcate petals, because other congeners herein presented have a cordate (sometimes sagitate) labellum and falcate petals.
Notylia yauaperyensis occurs in French Guiana, Venezuela, Brazil and Peru (Dunsterville and Garay, 1972;Govaerts et al., 2014).In Brazil, it is restricted to the north region, with records in Amazonas, Pará and Maranhão states (Pabst and Dungs, 1977;Barros et al., 2014).In the study area it was found blooming in May and November.
It is characterised, among other species of Notylia in the study area, by its smaller vegetative size (7-9 cm long), narrower flowers, which are usually white with orange maculae in the petals, and a sagittate labellum with a pubescent kell.
This unidentified species of Notylia was found growing in open palm forests blooming in February and March.
It is morphologically related to N. barkeri, but it presents a typical compacted caespitose vegetative development, shorter and widely elliptic leaves, fleshy flowers, and lateral sepals fused on the base, close to the region of insertion of pedicel.
It differs from O. bicornis by its sepals with papillae on the margins and callus of labellum with trichomes and papillae.
This species occurs from northern South America to Northeastern Brazil (Govaerts et al., 2014).In Brazil, it was recorded in the states of Amazonas, Pará, Roraima and Maranhão (Pabst and Dungs, 1977;Barros et al., 2014).In the study area it is a rare species, and was collected growing on evergreen riverine forests blooming in January and February.
Quekettia microscopica is characterised by its terete leaves, a paniculate inflorescence with a thin peduncle, yellow flowers and lateral sepals fused at the base, in a tubular structure.
This species is distributed from the Antilles to Tropical America (Govaerts et al., 2014).In Brazil, it is known to occur in the states of Acre, Amazonas, Amapá, Pará, Rondônia, Roraima, Tocantins, Maranhão and Mato Grosso (Pabst and Dungs, 1977;Barros et al., 2014), and was found with flowers in the study area from January to March and November.
Rodriguezia lanceolata can be easily recognized among the Oncidiinae in the study area by the set of following characters: pendent racemose inflorescences, flowers around 16 mm wide, pink to reddish, and have lateral sepals completely adnate with the base of the column, forming a noticeable calcar.
Trichocentrum fuscum is characterised by its obovate to oblong and erect-patent labellum, with base adnate to the column, in a tubular and strongly inflexed calcar.
This species differs from the other Orchidaceae in the study area by its inflorescence with a tough peduncle and a congested multi-flowered panicle, bearing flowers 6 mm wide, with white sepals and petals and yellow labellum callus.
Both Trichocentrum nanum and T. morenoi are quite similar in vegetative characters, but can be easily distinguished by its inflorescences and flowers.Trichocentrum nanum has a racemose inflorecence with 8-24 flowers, with are wider 14 mm, yellow with purple maculate on the petals and sepals and has a distinctive globose callus.In turn, T. morenoi has a short and erect panicle, with flowers smaller (ca.6 mm wide), petals and sepals white and a yellow callus.
In South America, with distribution in Venezuela and Brazil (Govaerts et al., 2014).This species occurs in the states of Amazonas, Pará and Maranhão, Brazil (Silva et al., 1995;Barros et al., 2014).In the study area, it was collected growing in secondary forests, blooming in April.
Trichopilia mutica is characterised by its cylindrical pseudobulbs, leaves linear-lanceolate, coriaceous and sulcate longitudinally, inflorescence with five flowers or less, petals and sepals whitish, labellum transluscent white with pink spots and base strongly concave, undulated margin and apiculate apex.