Rediscovery of Aponogeton lakhonensis A . Camus ( Aponogetonaceae ) : a long-lost aquatic plant of India

Aponogeton lakhonensis A. Camus is rediscovered after a gap of 123 years from India. The detailed morphology of the plant along with a comparative analysis with Aponogeton natans (L.) Engler & Krause has been provided in this study supported by photographic illustrations.

ISSN 0974-7907 (Online); ISSN 0974-7893 (Print) Family Aponogetonaceae is a monogeneric freshwater aquatic plant group belonging to the order Alismatales and comprising of around 58 species mostly distributed in the tropical and subtropical regions of Africa, Asia, and Australia (Chen et al. 2015;Yadav et al. 2015;De Silva et al. 2016). In India, the genus Aponogeton Linnaeus f. (1781) is known to have only eight species out of which, four are endemic (Yadav & Gaikwad 2003;Yadav et al. 2015). Aponogeton lakhonensis A. Camus was first described by Aimée Antoinette Camus in 1909 based on a collection made by F.J. Harmand in 1875 from Mount La-khon, Laos. It is the only species reported from the entire eastern India. Often, this species has been incorrectly labelled as Aponogeton natans (L.) Engler & Krause (1906) (Youhao et al. 2010. Hence a comparative analysis between both the species has been studied, enumerated and photographically presented below.
In India, this species was first collected in 1836 by an anonymous collector from Assam and again in 1898 by M.A. Hock from Jaboka, Sibsagar district, Assam post which there has been no further sightings nor any recollections from the entire country making it a regionally threatened plant species.
During a recent botanical survey to Dhemaji district of Assam conducted during 2020-2021, the authors came across an extremely striking aquatic plant with floating leaves and yellow inflorescence. On extensive studies and consultation with the existing literatures (Yadav & Gaikwad 2003;Tanaka et al. 2007;Youhao et al. 2010) and herbarium specimens (CAL499688, image!; CAL499690, image!), the aquatic plant was identified as Aponogeton lakhonensis A. Camus.
Flowering: March to October. Specimen examined: India, Assam, 1836 (CAL499688, species from India after 123 years. The plant has been located from the Poba Reserve Forest of Dhemaji district, Assam making it a new report of occurrence apart from

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the previous two localities in Assam. Pictures depicting its habit (Image 1,2) and a photo plate depicting the different parts of the plant (Image 3) along with a map (Figure 1) citing the present study location are provided to aid in its proper identification. Voucher specimens (DDM03) have been deposited at the Gauhati University Botanical Herbarium (GUBH), Gauhati University, Guwahati and at the ASSAM Herbarium, Botanical Survey of India, Eastern Regional Centre, Shillong. Aponogeton lakhonensis A. Camus and Aponogeton natans (L.) Engler & Krause are very similar in appearance and sometimes misidentified. Therefore, a comparative analysis between both the species has been studied and enumerated in Table 1 along with a photographical presentation (Image 4).

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The Journal of Threatened Taxa (JoTT) is dedicated to building evidence for conservation globally by publishing peer-reviewed articles online every month at a reasonably rapid rate at www.threatenedtaxa.org. All articles published in JoTT are registered under Creative Commons Attribution 4.0 International License unless otherwise mentioned. JoTT allows allows unrestricted use, reproduction, and distribution of articles in any medium by providing adequate credit to the author(s) and the source of publication.   Pp. 19663-19664 Two new additions to the orchid flora of Assam, India -Sanswrang Basumatary, Sanjib Baruah & Lal Ji Singh, Pp. 19665-19670 Wildlife art and illustration -combining black and white ink drawings with colour: some experiments in Auroville, India -M. Eric Ramanujam & Joss Brooks, Pp. 19671-19674