Rediscovery of Sewardiella tuberifera Kash. , a long-lost monotypic endemic Indian liverwort

: An extremely rare, long-lost, monotypic endemic, Indian liverwort, Sewardiella tuberifera Kash. has recently been recollected after a gap of over three-and-a-half decades from an altogether new location, the Mukteshwar region (2,171 m) of Nainital district in the Kumaun Himalaya, Uttarakhand. The remarkable rediscovery of this monotypic, endemic Himalayan liverwort is a significant finding for the world’s bryological treasure. Along with other rare Himalayan monotypic endemics such as Aitchisoniella himalayensis Kash. and Stephensoniella brevipedunculata Kash., the currently located sporiferous population of Sewardiella was discovered persisting in small, dispersed, sparse patches with 5–30 individuals. The currently spotted collection site is being considered a ‘bryological hotspot’. As the area develops as a popular ecotourism destination, the original habitat of these hepatics in a lime stone-dominated, south-west facing, unstable sloppy site at Mukteshwar is under constant pressure from several developmental activities. Hence, serious conservation steps are needed to protect this hotspot supporting Himalayan bryophyte jewels. To ensure long term perpetuation and conservation of red-listed hepatic taxa, an attempt is being made to translocate part of the population to ecologically and climatically identical safer site, including a developing ‘moss garden’ at Lingadhar (Nainital).


INTRODUCTION
Sewardiella Kash., a monotypic, endemic, and long-lost Indian liverwort genus of the phylum Marchantiophyta, class Jungermanniopsida, family Petalophyllaceae, order Fossombroniales, has been discovered after a long period of time in the Kumaun region of the western Himalaya (Bryophyte Specialist Group 2000). The genus Sewardiella is classified as 'Vulnerable' in the IUCN Red List due to its limited distribution in the Indian western Himalaya (Bryophyte Specialist Group 2000). Kashyap (1915) established and described this unusual genus based on a collection from Shimla (Himanchal Pradesh) and Mussoorie (Uttarakhand) in the western Himalayan region. Kashyap (1929) has described the morpho-taxonomic details of a single species as S. tuberifera. Occasionally, many workers collected and described Sewardiella from different localities of the western Himalaya, India (Pande et al. 1955;Pant 1983;Udar & Srivastava 1983a,b;Tewari & Pant 1984). The mycorrhiza and tuber formation of this liverwort was studied by Chalaud (1932). Pande & Mishra (1937) delineated the life history of this plant, and Mehra (1938) reported 18 numbers of diploid (2x) chromosomes from the archaesporial cell nucleus of this plant. A detailed embryological account of this extraordinary genus Sewardiella was provided by Mehra & Khanna (1950). Pande et al. (1955) reported this hepatic as of common occurrence in Nainital and environs. Udar & Srivastava (1983a,b) have also thoroughly described the documentation of rare and endangered liverworts in India, as well as their reproductive biology. Pant (1983) listed this taxon as threatened bryophyte of Kumaun Himalaya. Tewari & Pant (1984) made scanty collections of this plant in a sterile state from the Kumaun region, viz., Suyalbari (1,100 m), Chaubatia (1,820 m), and Dhakuri (2,500 m). Pant et al. (1994) have again stated that this taxon is on the 'red list hepatic'. After 1984, there is no report of the collection of this extremely rare, phylogenetically significant liverwort from any other part of the country. Recently, Singh (2008) marked this taxon as red list endemic hepatics. One of the authors (SDT) has revisited all the earlier mentioned sites, but no traces of its occurrence could be recorded. Due to drastically changing original habitat conditions, it has gradually disappeared from the site of its occurrence over the years. Fortunately, during a recent bryophyte survey and collection in the Kumaun region of the western Himalaya, a new location of this liverwort in a fully fruiting state was discovered in and around the Mukteshwar area of district Nainital (Uttarakhand). The currently encountered poor sporiferous Sewardiella population was observed as small, scattered, scanty patches ranging 5-30 individuals in extremely disturbed habitat conditions gripped by rapid urbanization and anthropogenic activities, as well as the enormous mounting pressure of ecotourism. Based on the earlier records as well as the present collection of many interesting Himalayan hepatics like Aitchisoniella, Stephensoniella, Athalamia, Cryptomitrium, Exormotheca, Fossombronia, Sewardiella, and Haplomitrium species from the anthropogenically disturbed site at Mukteshwar, this locality may be declared a unique 'bryological hotspot'. Hence, conservation measures are urgently needed to save this hotspot as well as the dwindling hepatic jewels of the Himalaya from unplanned urbanization and developmental activities.

MATERIAL AND METHODS
During the months of April (10 April 2021) to September (26 September 2021), a thorough survey and collection were conducted in and around the Mukteshwar area of district Nainital (29.4727 0 N & 79.6466 0 E) within an elevational range of 2,240-2,266 m ( Figure 1). Sterile patches of Sewardiella were first noticed at the end of September. Fortunately, in the first week of October (2 October 2021-6 October 2021), we were able to collect both sterile and copiously sporiferous thalli of S. tuberifera from a south-west facing, sloppy, lime stone hill site. Field as well as microphotographs of both gametophytic and sporophytic parts of the liverwort were taken. The identification was confirmed by Dr. S.D. Tewari based on the earlier collections made from Kumaun region (Tewari & Pant 1984). Underlying substrate pH was measured by means of pH meter. The voucher specimens have been deposited in the herbarium of Botany Department, I.P.G.G.P.G. College of Commerce, Haldwani, Nainital (SP 112, SP 154, SP 187, SP 204, SP 234) and cryptogamic herbarium of National Botanical Research Institute (NBRI), Lucknow (LWG/ SP 154, SP 204/ SD-2).

DISCUSSION
The 'butterfly-like' morphology of S. tuberifera, with a prominent apical tuber, makes this liverwort easily identifiable in the field, even with the naked eye, but it can also be confused with fern prothallus in a sterile state. Still, the fact that the species could not be found in its known locations and habitat conditions in the western Himalaya, where it was once abundant for a long time, is cause for concern and indicates the species' extreme rarity.

CONSERVATION MEASURES
If the lone surviving site of S. tuberifera in India, Mukteshwar, is not protected and conserved in time, this fragile liverwort will become extinct. Keeping this in mind, an attempt is being made by us to transplant this liverwort from the highly disturbed site to a relatively undisturbed site with more or less the same topographical habitat conditions (sloppy site). Another attempt is being made to transplant some populations in small patches by creating similar habitat conditions in the recently developed "Moss Garden" at Lingadhar (Nainital), in order to monitor long-term perpetuation and conservation progress. Some of the sporiferous material may be preserved in vitro in the future.
Author details: Sapana Pant, a PhD scholar working under the supervision of Dr S.D. Tewari in the field of bryophyte taxonomy and conservation. She has received Kumaun University gold medal in MSc. Recently she received the "young scientist award" at the 15 th Uttarakhand State Science and Technology Congress 2020-22 for the best oral presentation and so far, published eight research papers in national and international journals. Dr S.D. Tewari Professor and former Head of the Department of Botany Govt. Girls PG College of Haldwani. He has 40 years of research experience in the field of bryology with 80 research papers and three books of his credit. Currently, he has been given an opportunity to work as a chief advisor of India's first "Moss Garden" developed at Lingadhar, Nainital. Dr Prachi Joshi, assistant professor Department of Botany Govt. PG. College Ranikhet has 20 years of teaching and research experience. She is specialised in the field of phytosociological studies in bryophytes and angiosperms. She has 20 research papers and one book of his credit. Manisha Bhandari, a research scholar pursuing her PhD work under the supervision of Dr S.D. Tewari. Presently she is working in the field of bryo-systematics and Phytosociological studies of the Cedrus deodara forest at Lohaghat. Till now she has published nine research papers and one booklets on bryophyte diversity. Richa Arya currently working as a research student under the supervision of Dr S.D. Tewari and co-supervision of Dr Prachi Joshi. She is engaged in "Bryo-exploratory studies of various Forest Types along an Altitudinal Gradient. So far, she has published three research papers, and one booklet on bryo-diversity.

Author contributions:
The main and corresponding authors (S.Pant and S. D.Tewari) collected, identified the samples and finalized the initial draft prepared by co-authors (P Joshi, M. Bhandari and R. Arya).