Abstract
A new species of Ophioglossum, O. isanense, from Northeast Thailand is described and illustrated. It may be diagnosed from other congeners by a combination of morphological characters including: its smaller size, cylindrical rhizome, stoloniferous roots, brownish green common stalk and trophophylls, the presence of persistent leaf sheath at the top of the rhizome and by the unique structure of spores. Molecular study also supported it as a distinct species. A summary of the ecology and an IUCN conservation status of the new species are provided.
References
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<p>Brown, R. (1810) <em>Prodromus floræ Novæ Hollandiæ et Insulæ Van-Diemen : exhibens characteres plantarum quas annis 1802-1805</em>. Taylor, London, 163 pp. https://doi.org/10.5962/bhl.title.52309</p>
<p>Goswami, H.K. (2008) Recurrent variations in natural populations may indicate genomic involvements I. <em>Ophioglossum</em> L. and <em>Psilotum nudum</em> (L.) P. Beauv. <em>In</em>: Verma, S.C. (ed.) <em>Perspectives in Pteridophytes</em>. pp. 445–456. Bishen Singh Mahendra Pal Singh, Dehradun.</p>
<p>Hooker, W.J. (1823) <em>Exotic Flora</em> Vol. 1. Edinburgh, 56 pp.</p>
<p>Kachhiyapatel, R.N., Patil, S.M., Patel, S.K. & Rajput, K.S. (2018) Genus<em> Ophioglossum</em> L., from western part of India with special reference to Gujarat State. <em>Notulae Scientia Biologicae</em> 10 (3): 373– 378. https://doi.org/10.15835/nsb10310243</p>
<p>Komarov, V. L. (1914) <em>Repertorium Specierum Novarum Regni Vegetabilis</em> 13: 85.</p>
<p>Lindsay, S. & Middleton, D.J. (2012 onwards) <em>Ferns of Thailand, Laos and Cambodia</em>. Available from: http://rbg-web2.rbge.org.uk/thaiferns/ (accessed 20 August 2020)</p>
<p>Linnaeus, C. (1753) <em>Species Plantarum</em>. Imprensis Laurentii Salvii, Stockholm, 1200 pp.</p>
<p>Linnaeus, C.V.f . (1781) <em>Supplementum Plantarum</em>. Orphanotrophe, Brunswig, 443 pp.</p>
<p>IUCN Standards and Petitions Committee. (2019) <em>Guidelines for Using the IUCN Red List Categories and Criteria</em>. Version 14. Prepared by the Standards and Petitions Committee. Available from: http://www.iucnredlist.org/documents/RedListGuidelines.pdf (accessed 12 February 2021)</p>
<p>Patel, M. & Reddy, M.N. (2019) Revealing a new species of <em>Ophioglossum</em> (Ophioglossaceae-Pteridophyta) from India with palynological and phylogenetic implications. <em>Botany Letters</em> 166 (4): 425–433. https://doi.org/10.1080/23818107.2019.1636405</p>
<p>Patil, S.M., Kachhiyapatel, R.N., Patel, R.S. & Rajput, K.S. (2018) <em>Ophioglossum gujaratense</em>, a new species from Gujarat State, India.<em> Phytotaxa</em> 351 (4): 273–280. https://doi.org/10.11646/phytotaxa.351.4.3</p>
<p>Patil, S.M., Patel, S.K., Raole, V.M. & Rajput, K.S. (2020) <em>Ophioglossum jaykrishnae</em> (Ophioglossaceae): A species novo from Gujarat state. <em>Indian Fern Journal</em> 37: 237–243.</p>
<p>POWO (2020) <em>Plants of the World Online</em>. Available from: http://www.plantsoftheworldonline.org/ (accessed 20 August 2020)</p>
<p>Tagawa, M. & Iwatsuki, K. (1979) Ophioglossaceae. <em>Flora of Thailand</em>, Vol. 3 part 1. The Tistr Press, Bangkok, pp. 261–291.</p>
<p>Thiers, B. (2020 continuously updated). Index Herbariorum: A global directory of public herbaria and associated staff. Available from: http://sweetgum.nybg.org/science/ih/ (accessed: 20 August 2020).</p>
<p>Willdenow, C.V. (1802) <em>Nova Academia Erfurt</em> 2: 18.</p>
<p>Yadav, B.L. & Goswami, H.K. (2010) A new, pink-brown<em> Ophioglossum</em> (Ophioglossaceae) from India. <em>Bulletin of the National Museum of Nature and Science, Series B (Botany), Tokyo</em> 36 (4): 155–159.</p>
<p>Zhang, L., Fanc, X.-P., Petchsri, S., Zhoue, L., Pollawatn, R., Zhang, X., Zhouh, X.-M., Luc, N.T., Knappk, R., Chantanaorrapint, S., Limpanasittichaim, P., Suna, H., Gao, X.-F. & Zhang, L.-B. (2020) Evolutionary relationships of the ancient fern lineage the adder’s tongues (Ophioglossaceae) with description of <em>Sahashia</em> gen. nov. <em>Cladistics </em>36 (4): 1–14. https://doi.org/10.1111/cla.12408</p>