Notes on the taxonomy of Liparis petiolata (D.Don) Hunt & Summerh. [Orchidaceae], a new Synonym, typification and Red List Assessment in Indian Perspective

Liparis Rich. [ORCHIDACEAE-EPIDENDROIDEAE-MALAXIDEAE-MALAXIDINAE] represent one of the Orchid genera with rich species diversity. Pridgeon et al. (2005) have considered Liparis as polyphyletic which represent assemblage of taxa with diverse vegetative and floral morphology. The genus includes both terrestrial as well as epiphytic species. The plant size, nature of rhizome, pseudobulbs, number, position and nature of leaves, flower size, venation in petals and sepals, size, shape and ornamentation of labellum, nature of column and its wing are considered taxonomically important characters in species delimitation within this genus. Chase et al. (2015) reported 426 taxa under the genus Liparis globally which are distributed in India, China, SE Asia, Pacific Islands to Australia and some species found in Europe and North America. In India, the genus is represented by 42 species and 1 variety which are distributed mainly in the Himalayan region with some species found in peninsular India and Andaman & Nicobar Islands.

While working on the taxonomic studies of the genus Liparis in North-East India, the authors came across a species Liparis tigerhillensis A.P. Das & Chanda which was described in 1989 and considered endemic to the Darjeeling Himalaya. The type specimens mentioned in the protologue were not traceable and this species was never collected by anyone after its type collection. The description and illustration in its protologue were compared with Liparis petiolata (D. Don) Summerh. and found to have identical morphological features. Therefore, following the principle of priority as per Turland et al. (2025), Liparis tigerhillensis has been reduced here as a heterotypic synonym of Liparis petiolata. As the type specimens of Liparis tigerhillensis are not traceable in any of the designated herbaria, the illustration in its protologue (which is the only original material associated with this name) has been designated here as its lectotype. Liparis petiolata is distributed in India, Bhutan, China, Indo-China, Nepal and Thailand. In India, the species is recorded from Arunachal Pradesh, Meghalaya, Nagaland, Sikkim and West Bengal in the Eastern Himalaya and North-East India phytogeographic regions. Considering its distribution range in the country, declining population and habitat quality and with application of Criterion B of IUCN (IUCN, 2012a, b; 2024), this species has been assessed as ‘Vulnerable°’ in Indian perspective. A detailed description, coupled with information on its phenology, habitat, distribution and photographs is provided for easy recognition of the species. The taxonomic consequences on its synonymy and typification are discussed. The rationale for its red list assessment has also been provided.

Das and Chanda (1989) described Liparis tigerhillensis based on few plants collected from Tiger Hills, Senchal Forest Division of Darjeeling district. They differentiated it from Liparis rostrata and Liparis odorata but didn’t compare with Liparis petiolata. The type specimens mentioned in the protologue are not traceable in any of the designated herbaria, but the illustration and original description clearly indicate that it can not be differentiated from Liparis petiolata. Therefore, it is reduced under the synonymy of Liparis petiolata. As the type specimens of Liparis tigerhillensis are missing, the illustration in the protologue remains as the only original material and it is designated here as lectotype of the name Liparis tigerhillensis.

Liparis petiolata is a South-East Asian species distributed in India, Bhutan, China, Indo-China, Nepal, Thailand. In India the species is known from Arunachal Pradesh, Meghalaya, Nagaland, Sikkim and West Bengal. All the occurrence points in India were geo-referenced and distribution map was prepared in GeoCAT domain (Figure-2). There are four locations – one each at Arunachal Pradesh, Meghalaya, Nagaland and Sikkim-Darjeeling Himalaya. Few mature individuals were observed at Arunachal Pradesh and Sikkim during the present study. All these locations are subjected to threats like developmental activities, tourism, deforestation for expansion of agricultural land resulting in declining habitat quality. Sporadic harvesting was also observed for this species to be used as ornamental. Pollination and seed germination are vector dependent. The Extent of Occurrence (EOO) and Area of Occupancy (AOO) are calculated through GeoCAT as 165400.695 Km² and 116 km² respectively. Data on the past population size and decline is not available for this species. Considering the above threats, and by applying Criterion B of IUCN, this species is preliminarily assessed as Endangered [EN B2ab(iii, v)]. As the species is distributed in the neighbouring countries like Bhutan, China, and Nepal with continuous suitable habitat with India, there is a possible geneflow between these sub-populations. Therefore, as per the IUCN guidelines for regional assessments, the preliminary assessment has been downlisted to Vulnerable°. Habitat conservation, ex-situ conservation and further research are recommended conservation measures for this species.

ACKNOWLEDGEMENTS:

The authors are thankful to the Director of Botanical Survey of India, Kolkata, Head of Office of Botanical Survey of India, Sikkim Himalayan Regional Centre, Gangtok and the Vice Chancellor of Andhra University, Visakhapatnam for providing the research facilities and encouragements.

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