Orchid ’ s diversity at Tepequém ’ s Tepuy , Roraima , Brazil

The Orchidaceae family is one of the largest among the angiosperm, with more than 27000 species, 2,500 is endemic to Brazil, 871 species are found in the Brazilian Amazon. In the far north of Brazil, in the state of Roraima, is located the Tepequém Mountains, a Tepuy – mountain top with table shape – with relictual vegetation due to prolonged isolation. Historically, Tepequém was a site of diamond exploration, which caused changes in the landscape. However, with mining decay, ecotourism became the main economic activity. About 68% of Roraima’s territory is composed of conservation areas and indigenous lands, and the Tepequém Mountain is the only Tepuy found outside the protected areas. Thus, this study aims to describe the orchid flora found at Tepequém’s Tepuy, an area of ecological and economic importance for Roraima’s ecotourism. The survey was carried out through expeditions between the years of 2013-2015. The species were photographed, harvested and taken to Embrapa Roraima for identification, exsiccate confection and/or cultivation. The exsiccatae were deposited at Roraima’s Integrated Museum (Museu Integrado de Roraima – MIRR) and the Federal University of Roraima (Universidade Federal de Roraima – UFRR). Any orchid species deposited by other collectors was also considered. Thus, 20 genera and 34 species were registered at Tepequém. The genera with largest representation were the Epidendrum (7 spp.), Scaphyglottis (4 spp.) and Habenaria (3 spp.), with 70% of the other genera presenting one species only. 10% of Roraima’s orchid’s diversity is found at Tepequém. The diversity of habitats – forest, campina and savannah – found at Tepequém’s Tepuy allows the Orchidaceae species diversity and the unique flora with low similarities to other floristic surveys.


INTRODUCTION
The Orchidaceae family is one of the largest among the angiosperm, with more than 27000 species (THE PLANT LIST, 2016).A privileged orchid flora can be found in Brazil, with yearly reports of new species been publish in understudied places.Thus, floristic surveys covering this family are important to enlarge the available knowledge on orchid's diversity.
The Guiana Highlands can be found in northern South America, an area comprised by Brazil, Venezuela and Guyana, in which a great number of table-shaped Technical arTicle mountains, regionally called "Tepuy", can be found.A few are located at Roraima (RR), such as: the Roraima Mount (RR), the Tepequém Mountains (RR), Urutanim (RR), Uafaranda (RR) and Surucucus (RR).These areas remained isolated for a long time, resulting in a unique floristic unit (ALVES et al., 2007).With this in mind, Haffer (1992) pointed that studies were necessary to understand how this unique landscape came to be at the Amazon portion.
Throughout the 30-70 decades, the Tepequém was a site of diamond mining (BARROS, 1995).Due to dynamite usage several environmental changes occurred during this time, such as riverbed alterations and watercourse's silting (MAFRA and MARMOS, 2014).Nowadays, after mining prohibition, tourism became the main economic activity, showing the region's natural beauty and its unique natural resources.Interestingly, few studies were conducted in the area, and the floral surveys necessary for both tourism activities and environmental preservation remain to be done.
Studies carried out by Alves et al. (2007) point that soil drainage and poverty of nutrients, common features between the Tepuy and rupestrian fields, probably contributed to species' distribution pattern and similarity occurrence between these two landscapes.The authors reported great species' diversity for the Xyridaceae and Eriocaulaceae families at the Tepuy and rupestrian fields.On the other hand, the Rapateaceae family encompasses more than 100 species in the Tepuy, but is represented by the single endemic species Cephalostemon riedelianus Koern in the rupestrian fields (ALVES et al., 2007).However, this study did not include the monocotyledons.Thus, the Orchidaceae family was not compared.In order to contribute to the floristic inventory of the Amazon, especially regarding its mountainous areas, this study aimed to describe the Orchidaceae species found in Tepequém's Tepuy, an area with distinctive vegetation, of high ecological and economic importance for the Amazon region.

Study site
The Tepequém Mountain is located in a border area of Roraima, between Brazil and Venezuela, 50 km away from the municipality of Amajari.The mountain covers an area of 12000 Km², located in the center of a closed basin (03°45'54,6" N, 61°41'17,5" W).The altitude ranges from 550 to 1100 m, with humid tropical climate type Am (KÖPPEN CLASSIFICATION, 1948) and annual average temperatures between 22 and 24º C.During the rainy season, temperature below 20º C have been registered for the areas above 700 meters and at the mountain peak, with annual average rainfall of 2000 mm (BARBOSA, 1997).
The Orchidaceae species' survey was carried out through expeditions between the years of 2013-2015, covering both the dry and rainy seasons.The species were photographed, harvested and taken to Embrapa Roraima headquarters for identification, exsiccate confection and/or cultivation.Specimen's identification was performed based on specialized bibliography (COGNIAUX, 1893(COGNIAUX, -1896;;1898-1902;1904-1906;MIRANDA, 1996;LUZ and FRANCO, 2012).The exsiccatae were deposited at Roraima's Integrated Museum (MIRR) and at the Federal University of Roraima (UFRR).Orchid species deposited by other collectors were also considered.The species' geographic distribution was verified using the website Brazil's Flora (FLORA DO BRASIL 2020, 2016).Sorensen similarity index (SI) was calculated using the following formula: SI= 2a/2a+b+c, in which a represents the number of species in common, b and c represent the number of exclusive species in each area (MUELLER-DUMBOIS and ELLENBERG, 1974).

RESULTS
Orchidaceae species from 20 genera and 35 were found (Figure 2).The genera with largest representation were the Epidendrum (7 spp.), Habenaria (4 spp.) and Scaphyglottis (4 spp.), with 70% of the other genera presenting one species only.Forty-seven percent of the species found at Tepequém have a wide geographical distribution, even been found in other countries, been well disseminated in  The Orchidaceae species registered at Tepequém Mountain were compared to the flora found at Chapada Diamantina, Bahia (BA), at Caxiauanã National Forest, Pará (PA), and at Viruá National Park, Roraima (RR) using Sorensen similarity index.Results showed similarities of 5%, 4.6% and 20% between communities, respectively.This indicates that Tepequém's Tepuy orchidophilic flora has greater similarity to Viruá's, with only 20% of similar species.Silva et al. (1995) registered the occurrence of 378 species in an inventory regarding the Amazon orchids, in which 18 occur at the Tepequém Mountain.However, by the time in which the study was conducted, the occurrence of two species had not been recorded at Roraima: Cyrtopodium andersonii (Lamb.ex Andrews) R.br. and Cleistes rosea Lindl.After two decades, the number of species found at Brazilian Amazon increased more than twofold, for a total of 871 species (FLORA DO BRASIL 2020, 2016), in which all 35 species found at Tepequém Mountain are included.

DISCUSSION
There are records of 309 species distributed in 110 genera at Roraima, in which nine are endemic to the state and 26 are endemic to Brazil.This great variety of orchids' species results from the diversity in vegetation and terrain found in the state.This way, Roraima is the third state in of the Brazilian Amazon, with of the orchids' variety occurring at Tepequém mountaintop (FLORA DO BRASIL 2020, 2016).
As previously mentioned, the diamond mining that occurred during the 30-70 decades at Tepequém resulted in environmental alterations and degradation, possibly resulting in loss of biodiversity.However, nowadays, tourism is the main economic activity.The landscape diversity favored ecotourism, mainly through hikings to Paiva's, Barata's and Funil's waterfalls, in addition to Platô's trail (FERNANDES and SENHORAS, 2010;MAFRA and MARMOS, 20014), that becomes a true natural garden during the Epidendrum ibaguense Kunt.and Sobralia granitica G.A.Romero & Carnevali floration period.
Regarding the similarity between communities, Conceição and Pinari (2007) point that the common characteristics between the Tepuy and the rupestrian fields result in similar distribution patterns for the Xyridaceae and Eriocaulaceae families, which could indicate a high level of similarity among the Orchidaceae in both phytophysiognomies.However, when species found at Tepequém were compared to those found at Chapada two were found in both areas, Epidendrum Jacq.and Oeceoclades maculata (Lindl.)Lindl.On the other hand, when compared to the floristic survey carried out by Bastos and Berg (2012)  Comparisons between the floral surveys resulted in low species similarity when areas were compared, probably due the prolonged floral isolation in the Tepuy.The lack of floral surveys including monocotyledons in these environments impairs more specific comparisons, which in turn could point the ecological relationships that result in the local flora.Furthermore, Krahl et al. (2015) point the need of more studies regarding the pollination and reproduction processes of the orchids found at Brazil's north region.
Despite the technological advances in environmental sciences, it is still impossible to recover the lost biodiversity.When one species goes extinct, it is impossible to recover, or even repair, the lost environmental services.Thus, due to Tepequém's Tepuy orchidophilic flora uniqueness, the conservation of the area is of utmost importance.

CONCLUSIONS
The habitats diversity (forest, campina and savannah) found at the Tepequém's mountaintop is related to the Orchidaceae diversity found in the area.The Tepequém's Tepuy showed no similar flora when compared to the floral surveys carried out at the rupestrian fields, nor to the Chapada Diamantina or even the National Park of Viruá.The orchids flora found 20 genres and 35 species at Tepequém's Mountain confirms that the Tepuys have autochthonous vegetation.

Figure 1 .
Figure 1.Landscapes that form the Tepequém.A -Tepequém Mountain Plateau; B -Forest on the banks of Igarapé do Paiva; C -Steppe savannah; D -Savannah near the watercourse of a semi-perennial water; E -Rocky outcroppings; and F-Buritis' Vereda and artificial lakes resulting from the mining activity.

Table 1 .
List of Orchidaceae species found at Tepequém Mountain, Roraima, predominant habit and vegetation in which species were found.