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An annotated checklist of Myanmar orchid flora

Abstract Myanmar is situated in Southeast Asia, where species richness and diversity are very high. Myanmar orchid flora is very rich, but still poorly known because botanical explorations have sharply decreased in Myanmar since 1950. The present study provides a checklist of Myanmar orchid flora which includes 1040 species and 151 genera currently known from Myanmar, based on the herbarium specimens, literature and online databases. The number of species is increased by approximately 200 species more than that given in the checklist of Kress et al. (2003), mainly due to recent discoveries of new species to science and new records for Myanmar. There are 76 endemic species of Orchidaceae in Myanmar. It is estimated that ca. 150–300 species still remain as unidentified and are expected to be discovered in further studies on Myanmar orchid flora.


Introduction
Southeast Asia is a region of high species richness and endemism, encompassing four major global biodiversity hotspots, namely Indo-Burma hotspot, Sundaland hotspot, Wallacea hotspot and Phillipines hotspot (Myers et al. 2000, Mittermeier et al. 2011. Biodiversity in this region is under various threats to species survival, such as habitat loss and fragmentation, land use change, climate change and deforestation. Under such circumstances, Southeast Asian countries face various challenges for biodiversity conservation and the lack of financial and technical assets (Myers et al. 2000, Sodhi et al. 2004, Mittermeier et al. 2011. Myanmar is situated in Southeast Asia and is also part of the Indo-Burma biodiversity hotspot, with high species richness and diversity (Myers et al. 2000, Mittermeier et al. 2011. Due to its broad latitudinal range (tropical to subtropical), topographical (mostly mountainous) and climatic (monsoonal) factors, there are various types of ecosystems in Myanmar, from southern tropical evergreen rainforest ecosystem to northern subtropical montane forest ecosystem through central dry deciduous forests.
On the other hand, as biodiversity research is very limited in Myanmar, many species of fauna and flora still remain unidentified. Biodiversity conservation is urgently needed to secure the sustainability of existing biodiversity resources in Myanmar (Giam et al. 2010, Webb et al. 2010, Forest Department 2015). According to the checklist of Myanmar flora , there are 273 families, 2371 genera and over 11,800 species of vascular plants, including ca. 800 species of Orchidaceae recorded from Myanmar (Kress et al. 2003, Kurzweil andLwin 2014).
Botanical explorations have sharply decreased in Myanmar since 1950, leading to a large gap of knowledge on flora of Myanmar . Unlike neighbouring countries with intensive botanic investigation and a modern taxonomic treatment on orchid biodiversity, the orchid flora of Myanmar is very poorly known and lacks a modern taxonomic treatment (see Pearce and Cribb 2002, Ormerod and Sathish Kumar 2003, Ormerod 2005, Chen et al. 2009, Pedersen et al. 2011, Kurzweil and Lwin 2014. At the start of the 21 st century, botanical explorations resumed in Myanmar, with the support of international cooperation for biodiversity conservation and research. As a result, there are discoveries of species new to science and new species records for Myanmar orchid flora over recent years (Ormerod 2005, Tanaka et al. 2010, Kurzweil et al. 2010, Kurzweil and Lwin 2012a, b, 2014, Kurzweil 2013, Watthana et al. 2015, Aung et al. 2017, Jin and Kyaw 2017, Yang et al. 2017, Kurzweil and Ormerod 2018, Liu et al. 2018, Mu et al. 2019, Ya et al. 2019). In the review on Orchidaceae in the checklist of , there are many species needed to be revised taxonomically due to recent advances in orchid taxonomy and systematics. For example, the genera Drymoda Lindley (1838: 8), Ione Lindley (1853: 1), Monomeria Lindley (1830b: 61), Sunipia Lindley (1826a: 14, 21, 25), Trias Lindley (1830a: 60) have been merged into Bulbophyllum Thouars (1822: 3), leading to nomenclatural changes in Bulbophyllum (Pridgeon et al. 2014, Vermeulen et al. 2014).
In addition, there is a sharp increase in the number of species of Orchidaceae due to recent discoveries of species new to science and new species records for Myanmar. For example, one new species of Bulbophyllum Thouars (1822: 3), two new species of Calanthe Brown (1821: 573), three new species of Coelogyne Lindley (1821: 33), two new species of Dendrobium Swartz (1799: 2, 6: 82), two new species of Gastrodia Brown (1810: 330), one new species of Pinalia Lindley (1826b: 14, 21, 23), one new species of Odontochilus Blume (1858: 79) and one new species of Vanda Jones ex Brown (1820: 6: 506) have been described from Myanmar over recent years (Roberts et al. 2008, Ormerod and Wood 2010, Tanaka et al. 2010, Kurzweil 2013, Aung et al. 2017, Jin and Kyaw 2017, Yang et al. 2017, Kurzweil and Ormerod 2018. Recently Kurzweil and Ormerod (2018) also reported 38 new records for Myanmar, also leading to an increase in the number of species of Myanmar orchid flora. Under the main theme of biodiversity conservation and research, the present study investigates the species richness of Myanmar orchid flora, based on the field investigation, herbarium specimens, literature and online databases. The present study will contribute to the floristic studies and biodiversity conservation in Myanmar.

Study areas
In order to investigate species richness of Myanmar orchid flora, a programme of fieldwork has been conducted in almost all ecosystems across Myanmar. Seven protected areas across Myanmar, namely Hponkanrazi Wildlife Sanctuary and Hkakaborazi National Park of Kachin State, Popa Mountain Park of Mandalay Region, Nat Ma Taung National Park of Chin State, Alaungdaw Kathapa National Park of Sagaing Region, Taunggyi Bird Sanctuary and its adjacent areas of Shan State and Tanintharyi Nature Reserve of Tanintharyi Region, have been investigated two to five times in each protected area during 2014-2018 (Fig. 1).

Specimen collections and identification
In total, approximately 1,000 specimens of orchids were collected for vouchers, kept in PE and RAF (Thiers 2019, http://sweetgum.nybg.org/ih/). More than 75% of the total specimens were collected from Hponkanrazi Wildlife Sanctuary and Hkakaborazi National Park, Putao District, Kachin State, Northern Myanmar. Putao is the northernmost district of Myanmar where there are vast areas of primary forest with high species richness and diversity. The remaining proportions were collected from other study areas. In the collections, most species are Dendrobium species, Bulbophyllum species and Coelogyne species. The remaining proportions are species of common genera Eria, Liparis, and Oberonia. All collected specimens were taxonomically identified based on relevant literature, field notes, photographs taken during fieldwork, herbarium specimens (PE) and online herbarium specimens such as Kew Herbarium Catalogue and Chinese Virtual Herbarium (Seidenfaden 1992, Dressler 1993, Pedersen 1995, Pridgeon et al. 2001, 2005, Pedersen et al. 2002, Chen et al. 2009  and Lwin 2014, Chase et al. 2015, Chinese Virtual Herbarium 2018, Royal Botanic Gardens Kew 2018. For verification of taxonomic status of all species, literature and online databases, such as WCSP, were reviewed to confirm its respective taxonomic status (Pridgeon et al. 2001, 2005, Chen et al. 2009, Gardiner 2012, Gardiner et al. 2013, Vermeulen et al. 2014, Jin et al. 2014, Chase et al. 2015, Raskoti et al. 2016, 2017, Ng et al. 2018, WCSP 2019.

Investigation of herbarium specimens
In total, there were ca. 3,000 herbarium specimens examined, including specimens of our own collections (PE), Kew herbarium specimens (K) and specimen records from online herbaria: AMES, BM, E, GH, K, L, NY, P, US and W (Thiers 2019, http:// sweetgum.nybg.org/ih/). All available datasets of herbarium specimens (ca. 1500 specimens) and specimen photographs were downloaded from online herbaria and examined to enumerate the number of species and to investigate the species occurrences in Myanmar. The following are specimen records downloaded from each online herbarium, AMES (12 records), BM (420 records), E (496 records), GH (3 records), K (324 records), L (39 records), NY (116 records), P (87 records), US (81 records) and W (11 records . During our field trips in Myanmar, some old herbarium specimens at RAF (ca. 200 specimens) were also examined at herbarium (RAF) of Forest Research Institute in Yezin, Nay Pyi Taw.
As for species occurrences, the herbarium specimens (BM, E, K) provide the information on past record of species occurrences in Myanmar, for example, old collections (past 100 years) by some well-known plant collectors, such as Charles Parish, George Forrest, J. H. Lace, Frank Kingdon-Ward, W. A. Robertson, F. G. Dickason and C. W. D. Kermode during last half of the 19 th century and first half of the 20 th century. The herbarium specimens (PE) provide information on the current status of species occurrences across Myanmar.
In addition, some literature provides information on specimens from Myanmar that can be cited as specimen-based species occurrences in Myanmar (Kurzweil and Lwin 2015, Tanaka et al. 2015, Watthana et al. 2015, Aung et al. 2017, Jin and Kyaw 2017, Yang et al. 2017, Kurzweil and Ormerod 2018, Ding et al. 2019, Mu et al. 2019, Ya et al. 2019.

Verification of species occurrence and taxonomic status
The number of species in the updated checklist is a result of taxonomic attempts, mainly based on our own collections, all available herbarium specimens, checklist of  and all relevant literature. As for taxonomic status, we followed the updated classification of Orchidaceae (Chase et al. 2015) and all relevant papers of orchid taxonomy and systematics (Pridgeon et al. 2001, 2005, Chen et al. 2009, Gardiner 2012, Gardiner et al. 2013, Jin et al. 2014, Vermeulen et al. 2014, Raskoti et al. 2016, Raskoti et al. 2017, Govaerts 2018, Ng et al. 2018). In addition, all papers of new species descriptions and new records of Myanmar orchid flora were reviewed to identify the species occurrences and distribution in Myanmar , Roberts et al. 2008, Chen et al. 2009, Tanaka et al. 2010, Ormerod 2012, Pedersen et al. 2011, Kurzweil and Lwin 2012a, b, Kurzweil 2013, Kurzweil and Lwin 2014, Aung et al. 2017, Jin and Kyaw 2017, Yang et al. 2017, Kurzweil and Ormerod 2018, Ding et al. 2019, Mu et al. 2019, Ya et al. 2019.
Both the number of species and their taxonomic status were also verified with reliable online databases such as the World Checklist of Selected Plant Families (WCSP 2019), International Plant Names Index (IPNI 2012) and the Plant List (The Plant List 2013). Global Biodiversity Information Facility (GBIF 2019) and relevant online herbaria (AMES, BM, E, GH, K, L, NY, P, US and W) were also consulted to check the species occurrences of Orchidaceae in Myanmar.

Results
The present study results in a checklist of Myanmar orchid flora which includes 1040 species in 151 genera, with the number of species increased by ca. 200 species more than that given in the checklist of . The increase in number of species is mainly due to the recent discoveries of species new to science, as well as new records for Myanmar (Figs 2-4). In the last few years, there were 19 new species of Orchidaceae discovered from Myanmar, preliminarily assigned the conservation status based on the IUCN Red List Categories and Criteria (Table 1). In Myanmar, there are 76 endemic species of Orchidaceae which need high conservation attention (IUCN 2012, IUCN Standards and Petitions Subcommittee 2019) ( Table 2).
Local distribution information is provided for almost all species, usually at Region/ State (Provincial) level distribution ranges (Table 3). Specific distribution locality infor-     mation is also provided if known for some species. Voucher specimen citations are also provided for almost all species. In cases where herbarium specimens are lacking, the species occurrences are mainly based on the most reliable references of  and Kurzweil and Lwin (2014). By the number of species, most genera consist of one to ten species per genus, while genera Dendrobium and Bulbophyllum consist of more than 100 species in each (Table 4). The updated checklist is mentioned in the following detail.

Discussion
Botanical collections are still needed to cover the whole floristic diversity of Myanmar, because botanical explorations have sharply decreased in Myanmar since 1950 ). There is a large gap of knowledge on Myanmar flora. Perhaps there are many species to be discovered in Myanmar. The fundamental data on the number of plant species and its distribution range is still not fully known so that it needs much more research for effective plant conservation in Myanmar. In addition, it needs modern taxonomic treatments for each family or genus so as to update their classification. The orchid flora of Myanmar is very species-rich but still poorly known until now. The present study resulted in a checklist of Myanmar orchid flora which includes 1040 species and 151 genera. Botanical investigations are, however, still needed to better understand the orchid biodiversity of Myanmar. Compared with neighbouring countries with intensive orchid studies, Myanmar orchid flora have lagged behind being well-documented and well-studied. In this regard, it can be estimated that about 150-300 species still remain unexplored and are expected to be discovered in future studies on Myanmar orchid flora. As for conservation, all orchid species are legally protected by national legislation but most orchids are still under various threats for their survival, such as habitat loss due to deforestion and land use change. Orchids are, however, regarded as special plants in Myanmar society in terms of cultural ornamental purposes. Historically, Bulbophyllum auricomum Lindl. has been recognised as a royal flower in Myanmar during the period of Konbaung dynasty (1752-1885). Nowadays, it has been recognised as one of the national flowers of Myanmar, indicating the special attention of Myanmar society on orchids (Hinsley et al. 2018). Thus, it is obvious that the special role of orchids might enhance the orchid biodiversity conservation in Myanmar.
As for plant species richness in Myanmar, there are many new species described from Myanmar over recent years, for example, two new species of Annonaceae, one new species of Aristolochiaceae, one new species of Asteraceae, three new species of Balsaminaceae, one new species of Begoniaceae, two new species of Lamiaceae, one new species of Magnoliaceae, 10 new species of Orchidaceae, one new species of Phyllanthaceae and one new species of Zingiberaceae (Aung et al. 2017, Jin and Kyaw 2017, Tseng et al. 2017, Yang et al. 2017, b, Aung and Jin 2018, Ding et al. 2018, Liu et al. 2018, Li and Ren 2018, Ruchisansakun et al. 2018, Ya et al. 2019, Yao et al. 2018, b, Mu et al. 2019. Recently there are discoveries of two new plant familial records for Myanmar, namely Petrosaviaceae and Triuridaceae Mint 2018, Jin et al. 2018b). It is very obvious that species richness is very high in Myanmar, with evidence of recent discoveries of species new to science and new records. With many more botanical explorations, the knowledge gap on the flora of Myanmar can be filled in the future.

Checklist
The checklist consists of the following data (