﻿Indigoferajintongpenensis (Fabaceae, Papilionoideae, Indigofereae), a new species from Yunnan, southwest China

﻿Abstract Indigoferajintongpenensis, a new species of the subfamily Papilionoideae of Fabaceae, is described and illustrated from Yunnan, southwest China. The new species is characterised by having a prostrate habit, flexible stems and branches, as well as spreading, sub-basifixed, asymmetrically 2-branched trichomes covering the entire plant, discoid calyx, and racemose inflorescences 6–8-flowered, short, 1–2 (–3.5) cm in length, apparently shorter than the leaf. A distribution map and comparison of morphological diagnostic characters with its morphologically similar species are provided. Additionally, a preliminary conservation assessment of I.jintongpenensis is proposed following IUCN criteria.


Introduction
Indigofera L. is a legume genus belonging to the tribe Indigofereae of the subfamily Papilionoideae (Schrire et al. 2005;Azani et al. 2017).With approximately 750 species (Schrire et al. 2009), it is the third largest genus in Fabaceae.The genus is mainly distributed in tropical and subtropical regions worldwide with centres of species diversity primarily occurring in Africa (ca.550 species), the Sino-Himalayan region (ca.105 species), Australia (ca.50 species) and the New World (ca.45 species) (Schrire et al. 2009).Species of Indigofera are typically shrubs, but some are small trees, herbaceous perennials or annuals.The genus is characterised by a combination of the presence of medifixed 2-branched trichomes, pulvinate leaves, axillary simple racemes, anthers with appendiculate connective and flowers with an explosive pollen display (Hutchinson 1964;De Kort and Thijsse 1984).The genus includes economically important species with a variety of uses (Gerometta et al. 2020).Notably, I. tinctoria L. and I. suffruticosa Mill.are the principal sources for production of natural indigo (Zhang et al. 2019) China harbours a high level of diversity for Indigofera species, including many endemics, with the highest species diversity found in the south-western China (Yin et al. 1992;Gao and Schrire 2010).The first comprehensive revision for Chinese Indigofera was proposed by Craib (1913), recognising 57 species with 31 newly named.In the Flora Reipublicae Popularis Sinicae, Fang and Zheng (1994) recognised 81 species and nine varieties.In the latest treatment by Gao and Schrire (2010) in the Flora of China, 79 species and nine varieties were accepted, 45 of which are endemic.Recently, Zhao and Gao (2015), Zhao et al. (2020) and Liu et al. (2022) described three additional species of Indigofera in southwest China, highlighting the need for continued field exploration and taxonomical research of the genus in this area.
During our recent field surveys in preparation for a taxonomic revision of the genus Indigofera of Yunnan Province in southwest China, we collected an intriguing prostrate plant with a densely spreading indumentum on Jintongpen Mountain of Fumin County.Its racemose inflorescences are relatively short, bearing few flowers.After conducting extensive literature surveys and comparison with related specimens, we concluded this plant does not match with any of the previously described species.Therefore, it is described herein as a new species.

Taxonomy
Phenology.Flowering from June to September, fruiting from August to December.Etymology.The specific epithet "jintongpenensis" is derived from the type locality of the new species, the Jintongpen Mountain and the Latin suffix -ensis, indicating the place of origin or growth.
Distribution and ecology.According to the present investigations, Indigofera jintongpenensis is only found in its type locality, the Jintongpen Mountain of Fuming County, located in central Yunnan Province, southwest China (Fig. 5).With a maximum altitude of 2,817 m, the Jintongpen Mountain is the highest peak in Fuming County.I. jintongpenensis has been observed at elevations ranging from 2600-2817 m in the summit region of the mountain.It usually grows in the limestone scrub and its association includes Allium wallichii Kunth  Conservation status.Indigofera jintongpenensis is a rare species with a restricted distribution and small population size.It is only known from a single locality on the Jintongpen Mountain in the Fumin County, southwest China, which is not within any protected area.The estimated area of occupancy (AOO) is less than 20 km 2 .The total population size is estimated to be fewer than 250 mature individuals.Following the IUCN criteria (IUCN 2022), this new species should be classified as Endangered [EN (B2abiii,D)].
Taxonomic notes.Indigofera jintongpenensis is mainly characterised by having a prostrate habit, 2-branched trichomes that are spreading and asymmetrical, and racemose inflorescences that are 6-8-flowered and relatively short (mostly 1-2 cm in length).It is most morphologically similar to I. balfouriana Craib in terms of indumentum on various parts of the plant, as well as flower shape and size, but is clearly distinguished by the features pointed out in the diagnosis as well as others (Table 1).

Figure 1 .
Figure 1.Indigofera jintongpenensis sp.nov.A habit B fruit branch C flower (side view) D legume E style F standard G wing H keel I calyx (glabrous inside) J calyx (outside with spreading sub-basifixed 2-branched trichomes).

Figure 2 .
Figure 2. Indigofera jintongpenensis sp.nov.A habit B a portion of branchlet showing adaxial surface of leaflets C leaves (abaxial) D branchlet E stipules F leaves and inflorescence G inflorescence H legume.

Figure 4 .
Figure 4. Indigofera jintongpenensis sp.nov.A flower (lateral view) B calyx C standard D wing E keel F pistil and stamens G stamen H seeds.