The rediscovery of Uraria lacei Craib (Leguminosae) after 67 years from India

Abstract Manipur is one of the biodiversity-rich states in the North-Eastern region of India, and it is also part of the Indo-Burma biodiversity hotspot with rich plant diversity and endemism. Recent field exploration in the area has resulted in the rediscovery of Uraria lacei Craib after 67 years from its last collection in 1952. The rediscovery of this beautiful species fills a gap in the current distribution knowledge and should pave the way for its immediate conservation and propagation.


Introduction
The genus Uraria Desv. (Fabaceae-Papilionoideae-Desmodieae) contains about 20 species distributed in tropical Africa, South East Asia and Australia (Ohashi et al. 2006). In India, the genus has eight to 12 species predominantly found in tropical and sub-tropical regions (Baker 1879, Sanjappa 1992, Gaur 1999, Kirtikar and Basu 2001. Uraria lacei Craib is a beautiful species with dark blue inflorescence and is distributed in India, China, Laos, Myanmar, Thailand and Vietnam. The panicle of U. lacei is similar to that of U. oblonga (Wall. ex Benth.) H. Ohashi & K. Ohashi (Ohashi et al. 2018). In India, U. lacei is reported from the states of Nagaland, Manipur, Mizoram and Bihar (Sanjappa 1992). However, published literature and herbarium data suggests that, although the species was mentioned in the recent floras of Manipur (Singh et al. 2000) and Mizoram (Singh et al. 2002), these records were based on older collections. During a field study in November 2019 by the first author to North East India, the species was collected in flowering and fruiting stages from a hillslope at the only floating National Park (Keibul Lamjao National Park, Bishnupur, Manipur) in the world. After compiling all the data available in the public domain and specimens in different herbaria, it was observed that the last collection was from 11 September 1952 (D.B. Deb 585, CAL!). In the past 67 years, the species was not recollected from its occurrence in India, therefore, this certainly raises questions about its current status, conservation and existence in nature. Detailed description, taxonomic notes and colour photographs of U. lacei are provided here.

Methods
All the published literature were scrutinized for the probable localities or distribution of Uraria spp. in India. With that distribution data, a field survey was conducted during October-November 2019 in the states of Assam, Nagaland, Manipur and Meghalaya of India to collect plants of Uraria spp. Fresh specimens of U. lacei were collected in flowering and fruiting stages from Manipur. The flowering twigs were packed in airtight polybags, flowers and fruits were separately collected in collection tubes containing 70% ethanol for further studies. Field notes recorded included habit, habitat, number of individuals in the population, geo-coordinates, and elevation data. In transit camp, the specimens were pressed and dried on blotting sheets. Upon reaching the institute, they were processed in the herbarium following standard herbarium procedures (Jain and Rao 1977). All the collected samples were dissected and were examined under stereo microscope (LEICA S8 APO, Wetzler, Germany) and described. Taxonomic literature and protologues were studied and compared for identification (Hasskarl 1844;Clarke 1889;Lecomte 1920;Haines 1921;Deb 1961;Thuan et al. 1987;Sanjappa 1992;Sha 1994;Singh et al. 2000;Singh et al. 2002;Kumar and Sane 2003;Ohashi et al. 2006;Puhua et al. 2010).

Uraria lacei
Phenology. Flowering from October to November, fruiting from November to December. Conservation status. Based on the available literature in the public domain, and our recent field studies, we suggest that U. lacei can be provisionally considered under the 'Data deficient' category of IUCN (IUCN 2019). However, a further assessment of the threat operating on the species in question needs to be done as per IUCN guidelines.

Discussion
Uraria lacei was first collected by C.B. Clarke on 19 Oct 1885 from Kohima, Nagaland, India. He published the novelty as U. paniculata C.B. Clarke in 1890, but was unaware of the fact that the same name exists for a different type U. paniculata Hassk. in 1844, thus making it as a later homonym. Gagnepain, in 1920, realised this and renamed it U. clarkei Gagnepain, giving credit to C.B. Clarke. In the meantime, Craib (1910) already published it as U. lacei Craib, thereby it became the accepted name with priority. Uraria lacei was named after the collector of the type specimen, John Henry Lace, a famous botanist and forester in India, Myanmar, Pakistan, etc. His collection period was from 1889 to 1912. There are many species named after him including Styrax lacei W.W. Smith (Styracaceae), Parastyrax lacei (W. W. Smith) W. W. Smith (Styracaceae), Derris lacei Dunn (Fabaceae), and Euphorbia lacei Craib (Euphorbiaceae).
Uraria lacei is completely different from other species of Uraria in its inflorescence. Although the panicle resembles U. oblonga (Wall. Ex Benth.) H. Ohashi & K. Ohashi, it differs in having trifoliolate leaves rather than the unifoliolate leaves of the latter. The field observation revealed that the rediscovered population had about 20 individual plants within 2 m 2 area on the slope of a small hill at Keibul Lamjao National Park, Bishnupur. There were both young saplings as well as mature 2-3 m tall plants. Most of the plants were in flowering and fruiting condition. The soil was sliding due to clearance for road and mostly consisted of small pieces of rocks. The plants were growing with grasses and pines.
While going through the protologue and various literature, it was observed that the species is uniformly described to have terminal inflorescence. However, we observed both terminal as well as axillary panicle during the field survey (Fig 3). The protologue also suggested the pods to be "fere glabrum" (i.e. almost smooth), which can also mean there might be scarce minute hairs that are not noticeable. On the plants that we collected, the glandular hairs were clearly visible with naked eyes, but were not very dense. Unlike the dense glandular haired pedicel described by Ohashi et al. 2006 from China, the specimens collected were observed to have minute hooked hairs on its pedicels. Thuan et al. (1987) described the calyx as glabrous while Ohashi et al. (2006) described the calyx as densely glandular hairy. Our specimens were neither glabrous nor densely glandular hairy, but were scarcely glandular hairy. As observed in the field, the plants rarely have 4-foliolate leaflets (Fig 3).
As the plant has beautiful inflorescence and foliage, it would therefore be well-suited for domestication as an ornamental plant. Keibul Lamjao National Park, Manipur (India) is itself a protected area but anthropogenic activities like tourism is allowed in the buffer zone, therefore the vulnerability of U. lacei still cannot be ruled out. We could not locate any other population nearby to the present location and, given its rarity, there is an urgent need to conserve the population of this species in its present locale. Furthermore, species specific habitats need to be identified using ecological niche modelling (ENM) tools and saplings multiplied using both macro as well micro-propagation techniques, should be planted in the specific habitats to ensure the in-situ conservation of the species.