Mô tả loài Thiết mi mới ở miền Nam Thismia mucronata

Thismia mucronata (Thismiaceae), a new species from Southern Vietnam


1. Joint Russian-Vietnamese Tropical Scientific and Technological Center, CauGiay, Hanoi, Vietnam. e-mail: max.nuraliev@gmail.com

2. Faculty of Biology, M.V. Lomonosov Moscow State University, 1, 12, Leninskie Gory, 119234 Moscow, Russia.
3. A.N. Severtsov Institute of Ecology and Evolution of the Russian Academy of Sciences, Leninsky 33, Moscow, Russia.

Tóm tắt: Thismia mucronata, một loài mới của Thismiaceae, đã được mô tả và minh họa. Loài được phát hiện vào năm 2013 trong một cuộc khảo sát thực vật ở một khu rừng trong vùng lân cận của thị trấn Bảo Lộc (tỉnh Lâm Đồng, miền Nam Việt Nam). Thismia mucronata được đặc trưng bởi rễ giống hình con sâu và lá đài, tràng bên trong dạng mũ tế. Nó khác với loài có liên quan chủ yếu do đài, tràng  bên trong và các phần phụ ngắn và ép dẹt, cùng giống như một mũi ngắn, mũ hẹp mà không có hố, vòng gần như ngang và sự vắng mặt của các tuyến trên nhị hoa. Một khóa để định loại các loài Thismia của Việt Nam cũng được cung cấp.

Abstract: Thismia mucronata, a new species of Thismiaceae, is described and illustrated. The species was discovered in 2013 during a botanical survey of a forest in the vicinity of Bao Loc town (Lam Dong province, Southern Vietnam). Thismia mucronata is characterised by vermiform roots and mitriform inner tepals. It differs from related species mainly by the short and appressed to each other appendages of inner tepals, which together resemble a short mucro, the narrow mitre without foveae, the almost horizontal annulus and the absence of interstaminal glands. A key to Vietnamese species of Thismia is provided.
Keywords: Thismia, taxonomy, key, mycoheterotrophic plants, Southern Vietnam, Bao Loc, flora, biodiversity

Introduction: Thismia Griffith (1844: 221) is a genus of small, terrestrial, achlorophyllous, mycoheterotrophic, herbaceous plants. The genus along with four other genera of similar habit is currently placed in the family Thismiaceae, order Dioscoreales (Stevens 2001, Merckx et al. 2013) or less often Burmanniales (Takhtajan 2009). The exact phylogenetic relationships 
and taxonomic placement of this genus and its allies are still to be evaluated (APG 2009, Delin et al. 2010, Merckx et al. 2013). The main point of uncertainty is the phylogenetic position of Tacca Forster & Forster (1775: 69; Taccaceae), which appeared to be nested within Thismiaceae in some molecular-based phylogenetic reconstructions (Merckx & Bidartondo 2008, Merckx et al. 2009, 2010, Merckx & Smets 2014), making the family Thismiaceae paraphyletic. Moreover, the monophyly of Thismia itself has not been widely supported by cladistic analyses of molecular and morphological data sets (Merckx et al. 2006, 2009, Yokoyama et al. 2008, Merckx & Smets 2014).
 The genus Thismia is the largest within Thismiaceae and includes about two thirds of its species (Govaerts et al. 2011, Merckx et al. 2013). Merckx & Smets (2014) listed 50 known species of Thismia, and at least three more species were described after their review (Li & Bi 2013, Dančák et al. 2013, Truong et al. 2014). The genus is distributed from subtropical Asia to temperate Australia and in America, mainly in tropical evergreen forests (Maas-Van de Kamer 1998, Li & Bi 2013, Dančák et al. 2013, Merckx et al. 2013, Merckx & Smets 2014), with the highest species diversity in Borneo and Malay Peninsula (Chantanaorrapint 2012, Tsukaya & Okada 2012).
 Recently, many news species of Thismia have been discovered, in particular from various Asian countries. For instance, the number of species was estimated as around 35 several years ago (Yang et al. 2002, Chantanaorrapint 2008), which means description of ca. 15 species during the past decade. In Asia, new species have been recently reported from Taiwan (Yang et al. 2002, Chiang & Hsieh 2011), Yunnan (Li & Bi 2013), Vietnam (Larsen & Averyanov 2007, Truong et al. 2014), Thailand (Chantanaorrapint 2008, 2012) and Borneo (Kiew 1999, Tsukaya & Okada 2005, 2012, Dančák et al. 2013). Several significant range extensions in Asia have been also published (Chantanaorrapint & Sridith 2007, Chantanaorrapint & Chantanaorrapint 2009, Ho et al. 2009). Due to the paucity of collections, a considerable number of Thismia species are believed to be extremely rare. On the other hand, certain difficulties in field observations of these plants were pointed out, including their small sizes and ephemerality of above-ground parts (Stone 1980, Yang et al. 2002, Larsen & Averyanov 2007, Chantanaorrapint 2012, Tsukaya & Okada 2012, Dančák et al. 2013, Merckx & Smets 2014).
 Four species of Thismia have been ever reported from Vietnam, but only one of them—T. javanica J.J.Smith (1910: 32)—is listed in the Flora of Vietnam (Pham Hoang Ho 2000). Two additions—T. annamensis K.Larsen & Averyanov (2007: 13) and T. tentaculata K.Larsen & Averyanov (2007: 16)—were made by Larsen & Averyanov (2007). The latter ....
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