Polygala L. is the largest genus in the family Polygalaceae, but the estimates of the number of species vary widely. Paiva (1998) recognized 725 species while Eriksen & Persson (2007) included 300-350 species and Pastore (2018a) about 580 species. The genus is widely distributed throughout the world except in the Arctic, Antarctic, and New Zealand (Paiva 1998). The main centres of diversity are known from South Africa and the Americas (Kerrigan 2012). Pastore & al. (2017) and Mota & al. (2019) considered Polygala as a non-monophyletic genus. Based on Abbott (2009), Pastore & al. (2019) recognized two clades in Polygala s.str., namely, New World clade comprising 213 species under three sections and the Old World clade with 349 species in 11 sections. Polygala is characterized by the presence of 8 (rarely 6) monadelphous stamens (in a single semi-circular ring), two petaloid inner and three smaller outer sepals, and the dehiscent capsules containing two pubescent caruncular seeds (Chodat 1891; Eriksen 1993; Paiva 1998; Uðurlu 2020). Chandrabose & Nair (1981) reported 15 species from South India while 27 species were reported in India by Banerjee (1993). Kerrigan (2008, 2012) in a treatment of Polygala from northern Australia, recognized 45 species, of which 26 species and four varieties were newly described. A key for the identification of all the 50 species found in Australia were also provided in this work. Recently several new taxa of Polygala have been described: P. azizsancarii Dönmez from Turkey (Dönmez & Aydin 2018); P. mazandaranica Sarvi & Faghir and P. guilanica Sarvi & Faghir from North Iran (Sarvi & al. 2020, 2021); P. bringelii J.F.B.Pastore & Antar, P. capitolensis J.F.B.Pastore, P. herbiola var. minensis J.F.B.Pastore, P. jardimii J.F.B.Pastore, P. kalunga J.F.B.Pastore, P. michelliana J.F.B.Pastore, P. paganuccii J.F.B.Pastore, P. petricola J.F.B.Pastore, P. tocantinensis J.F.B.Pastore & Antar and P. veadeiroensis J.F.B.Pastore from Brazil (Pastore 2018a, 2018b; Pastore & al. 2021a, 2021b; Pastore & Antar 2021; Pastore 2022) and P. sandiaochiaoensis S.S.Ying from Taiwan (Ying 2020).

During field work in the floristically rich Idukki district of Kerala in the southern Western Ghats, we found an unrecognized species of Polygala resembling P. sibirica L. and P. rosmarinifolia Wight & Arn. After careful comparison of morphological characters in living and herbarium specimens (CALI), and after consulting relevant literature (Adema 1966; Chandrabose & Nair 1981; Banerjee 1993; Banerjee & Balakrishnan 2005; Chen & al. 2008; Ranjan 2009; Kerrigan 2008, 2012; Yang & Chen 2013; Dönmez & Aydin 2018; Pastore 2018a, 2018b; Pastore & al. 2019; Sarvi & al. 2020; Ying 2020; Pastore & al. 2021a, 2021b; Pastore & Antar 2021; Sarvi & al. 2021; Pastore 2022) we found that the entity in question is consistently distinct from all other species of the genus and is described here as new. The new species falls under Polygala subgenus Polygala.

Specimens collected were preserved in 4% formalin and 70% ethanol for detailed study. Photographs of habitat and habit were taken with a 77D DSLR camera (Canon, Japan). Floral details were studied using stemi 508 stereo microscope equipped with axiocam 105 color camera (Zeiss, Germany). The description was prepared by examining all available specimens and the terminologies followed Simpson (2006), Kerrigan (2008, 2012), and Pastore (2018a, 2018b). Herbarium sheets were prepared by conventional methods (Bridson & Forman 1991). The identity of the species was confirmed by comparing the types and protologues of the related species. For scanning electron microscopy (SEM), the seed samples were fixed in FAA and dehydrated by passing through an ethanol series. They were then critical point dried and mounted on to stubs using double-side adhesive tape, sputter coated with gold using SPI module sputter coater and examined under Gemini SEM 300 (Zeiss, Germany).

Taxonomic treatment

Polygala idukkiana Vishnu & Nampy, sp. nov. Type: India, Kerala, Idukki district, Kottppara-Mullaringad, 10°00’02”N, 76°47’52”E, ± 318 m, 2 Oct. 2021, Vishnu Mohan & Santhosh Nampy 176330 (holotype: CALI!; isotype: K!). Figs. 1-3.

Diagnosis.--Polygala idukkiana resembles P. rosmarinifolia by its inflorescence pattern and hairy seeds and to P. sibirica by its 3-lobed aril, but differs from the former, by its lavender flowers and hispid inner sepals (vs. yellow flowers and glabrous inner sepals) and from the latter by its lanceolate leaves, ciliate capsules, and non-hooded, equal sized arils (vs. elliptic leaves, glabrous capsules and hooded unequal sized arils).

Description.--Erect subshrubs, 20-50 cm tall. Roots not tuberous. Stem branched from base, cylindrical, striated, tomentulose, green. Leaves alternate; lamina lanceolate, 1.5-5.5 × 0.5-2.2 cm, acute at apex and base, entire and revolute along margins, sparsely tomentose on both surfaces; petioles 1.5-2 mm long, tomentulose. Racemes axillary, erect, 3-5 mm long, 3-5-flowered. Flowers 6-9 mm diameter; pedicels 3-5 mm long, puberulous; bracts 3, elliptic, 0.9-1.4 × 0.4-0.5 mm, rounded at apex and base, ciliate at margins. Sepals 5, persistent in fruit, green; upper outer sepals 2, free, lanceolate, 2-3 × 1 mm, narrowly acute at apex, ciliate; lower outer sepals 1, lanceolate, 4 × 1.4 mm, acuminate at apex, entire; inner sepals (wings) 2, petaloid, elliptic-lanceolate, 5-6 × 2-3 mm, mucronate at apex, wider at middle, ciliate, slightly coriaceous, hispid, reddish white. Petals 3, upper petals obliquely obcordate, 7-8 × 4-5 mm, lavender with violet streaks, retuse at apex, clawed, entire; lower petal, clawed, boat shaped, 6-7 × 2.5-3 mm; crest (dorsal appendages) 10-12-lobed in 2 bundles, violet; lateral lobe obliquely ovate. Stamens 8, monadelphous; fused at the base; staminal sheath 4.5-6 mm long, surrounding the style, adherent to upper petals; anthers obconical, 0.5-0.6 mm long. Ovary orbicular, 1.8 mm diameter, slightly oblique at apex; style strongly hooked, 6 mm long, inclined, terminated by an oblique cymbiform pre-stigmatic cavity. Capsules winged, orbicular, 6-7 × 4-5 mm, emarginated at apex, compressed, ciliate, 2-seeded; wings 2-3 mm wide. Seeds widely ovate, 3-3.7 × 2.8-3 mm, arillate, brown-black, strongly hirsute with dense silky white hairs; hairs 0.3 mm long, of equal length throughout; testa colliculate. Aril head reduced; lobes 3, equal, 2-2.2 mm long, non hooded.

Etymology.--The epithet ‘idukkiana’ refers to the floristically rich Idukki district, where the type locality belongs.

Distribution and habitat.--Known from Kattadikkadavu and Kottppara in Idukki district of Kerala state (Fig. 4), in the southern Western Ghats, at 318 m elevation, where it occurs in shady areas, as undergrowth of Gliricidia sepium (Jacq.) Kunth, Anacardium occidentale L., Artocarpus heterophyllus Lam., Macaranga peltata Boiv. ex Baill., etc., and also in open lands. The associated plants include Selaginella sp. (Selaginellaceae), Hyptis suaveolens (L.) Poit. (Lamiaceae), Microstachys chamaelea (L.) Muell. (Euphorbiaceae), Justicia sp. (Acanthaceae), Osbeckia aspera (L.) Blume (Melastomataceae), Chromolaena odorata (L.) King & Robins. (Asteraceae), Mimosa pudica L. (Fabaceae), and Spermacoce ocymoides Burm.f. (Rubiaceae).

Phenology.--Polygala idukkiana was collected with flowers and fruits in October. Flowering may start in September and extend up to November.

Provisional conservation status.--Polygala idukkiana is known only from two localities with less than 25 mature individuals. The localities are separated by a distance of around 2 km and the Area of Occupancy (AOO) falls below 0.2 km². Since the localities are tourist destinations, there are chances of reduction in the number of plants in the near future. More field work is needed in similar habitats to assess the population size and full geographical extent. Hence the species is provisionally categorized here as Data Deficient (DD) as per IUCN Red List Categories and Criteria (IUCN 2022).

Notes.--The presence of crested keel places Polygala idukkiana in Polygala subgenus Polygala. The new species is unmistakable in the field, due to its violet streaked lavender showy flowers, fimbriate-straight floral appendages (crest) and a well developed keel pocket. The flower is white in bud stage, gradually turning lavender and finally turns white. A morphological comparison of P. idukkiana, P. sibirica, P. rosmarinifolia and P. chinensis are provided in Table 1.

Additional specimen examined.-India. Kerala: Idukki district: Kattadikkadavu, 9°58’51.6”N 76°49’49.9”E, c. 400 m, 1 Oct. 2021, Vishnu Mohan & Santhosh Nampy 176389 (CALI).

Key to the Polygala species in Kerala (modified after Banerjee & Balakrishnan 2005 )