Polygala idukkiana (Polygalaceae), a new species from the southern Western Ghats, India

INTRODUCTION

Polygala L. is the largest genus in the family Polygalaceae, but the estimates of the number of species vary widely. Paiva (1998)Paiva J.A.R. 1998. Polygalarum Africanum et madagascariensium prodromus atque gerontogæi generis Heterosamara Kuntze, a genere Polygala L. segregati et a nobis denuo recepti, synopsis monographica. Fontqueria 50(4): 1-15. recognized 725 species while Eriksen & Persson (2007)Eriksen B. & Persson C. 2007. Polygalaceae. In Kubitzki K. (ed.), The families and genera of vascular plants vol 9: 345-363. Springer, Berlin. included 300-350 species and Pastore (2018a)Pastore J.F.B. 2018a. Polygala veadeiroensis (Polygalaceae), a new species of Polygala endemic to Chapada dos Veadeiros, Goiás, Brazil. Kew Bulletin 73: 37. about 580 species. The genus is widely distributed throughout the world except in the Arctic, Antarctic, and New Zealand (Paiva 1998Paiva J.A.R. 1998. Polygalarum Africanum et madagascariensium prodromus atque gerontogæi generis Heterosamara Kuntze, a genere Polygala L. segregati et a nobis denuo recepti, synopsis monographica. Fontqueria 50(4): 1-15.). The main centres of diversity are known from South Africa and the Americas (Kerrigan 2012Kerrigan R.A. 2012. A treatment for Polygala of northern Australia. Australian Systematic Botany 25: 83-137.). Pastore & al. (2017)Pastore J.F.B., Abbott J.R., Neubig K.M., Whitten W.M., Mascarenhas R.B., Mota M.C.A. & van den Berg C. 2017. A molecular phylogeny and taxonomic notes in Caamembeca (Polygalaceae). Systematic Botany 42: 54-62. and Mota & al. (2019)Mota M., Abbott J.R., Salas R.M., Neubig K.M. & Pastore J.F.B. 2019. Three lonely Argentines: Toward a new generic delimitation in Polygalaceae. Taxon 68: 1-15 considered Polygala as a non-monophyletic genus. Based on Abbott (2009)Abbott J.R. 2009. Revision of Badiera (Polygalaceae) and phylogeny of the Polygaleae. Dissertation, University of Florida, Gainesville., Pastore & al. (2019)Pastore J.F.B., Abbott J.R., Neubig K.M., van den Berg C., Mota M., Cabral A. & Whitten W.M. 2019. Phylogeny and biogeography of Polygala (Polygalaceae). Taxon 68: 673-691. 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 1891Chodat R. 1891. Monographia Polygalacearum. Premiere partie. Mémoires de la Société de Physique et d’Histoire Naturelle de Genève 7: 1-143.; Eriksen 1993Eriksen B. 1993. Phylogeny of the Polygalaceae and its taxonomic implications. Plant Systematics and Evolution 186: 33-55.; Paiva 1998Paiva J.A.R. 1998. Polygalarum Africanum et madagascariensium prodromus atque gerontogæi generis Heterosamara Kuntze, a genere Polygala L. segregati et a nobis denuo recepti, synopsis monographica. Fontqueria 50(4): 1-15.; Uðurlu 2020Uðurlu A.Z. 2020. Comparative capsule and seed morphology of Polygala L. (Polygalaceae) species in Turkey with implications for taxonomy. Plant Biosystems 154: 189-196. ). Chandrabose & Nair (1981)Chandrabose M. & Nair N.C. 1981. The genus Polygala L. (Polygalaceae) in Andhra Pradesh, Kerala, and Tamil Nadu (South India). Proceedings of Indian Academy of Science (Plant Sciences) 90: 107-127. reported 15 species from South India while 27 species were reported in India by Banerjee (1993)Banerjee R.N. 1993. Polygalaceae. In Sharma B.D. & Balakrishnan N.P. (ed.), Flora of India, vol. 1: 451-493. Botanical Survey of India, Kolkata.. Kerrigan (2008Kerrigan R.A. 2008. A taxonomic revision of Polygala L. in northern Australia. Thesis, James Cook University, Australia. , 2012Kerrigan R.A. 2012. A treatment for Polygala of northern Australia. Australian Systematic Botany 25: 83-137.) 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 2018Dönmez A.A. & Aydin Z.U. 2018. Polygala azizsancarii (Polygalaceae), a new species from Mardin Province, SE Turkey. Phytotaxa 340: 255-262. ); P. mazandaranica Sarvi & Faghir and P. guilanica Sarvi & Faghir from North Iran (Sarvi & al. 2020Sarvi A., Beygom F.M. & Shahi S.R. 2020. Polygala mazandaranica (Polygalaceae), a new species from Mazandaran province, North Iran. Phytologia Balcanica 26: 461-469., 2021Sarvi A., Beygom F.M. & Shahi S.R. 2021. Polygala guilanica (Polygalaceae), a new species from Guilan Province, North Iran. Phytotaxa 513: 141-151.); 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 2018aPastore J.F.B. 2018a. Polygala veadeiroensis (Polygalaceae), a new species of Polygala endemic to Chapada dos Veadeiros, Goiás, Brazil. Kew Bulletin 73: 37., 2018bPastore J.F.B. 2018b. A new species and new combination in Polygala sect. Timutua series Timoutoideae from Brazil. Kew Bulletin 73: 51.; Pastore & al. 2021aPastore J.F.B., Motta M., Amano E. & Agustina M. 2021a. Disentangling Polygala obovata complex (Polygalaceae), with a description of three new species for Brazil. Systematic Botany 46: 985-997., 2021bPastore J.F.B., Flaviano S.S., Pivari M.O.D., Anastacio A.C.S.A. & Amano E. 2021b. Polygala petricola (Polygalaceae), a new species from Brazil. Edinburgh Journal of Botany 78: 356. ; Pastore & Antar 2021Pastore J.F.B., Abbott J.R., Neubig K.M., Whitten W.M., Mascarenhas R.B., Mota M.C.A. & van den Berg C. 2017. A molecular phylogeny and taxonomic notes in Caamembeca (Polygalaceae). Systematic Botany 42: 54-62. ; Pastore 2022Pastore J.F.B. 2022. Revision of the ‘Polygala herbiola group’ (Polygalaceae): a new species and a new variety. Kew Bulletin 77: 221-232.) and P. sandiaochiaoensis S.S.Ying from Taiwan (Ying 2020Ying S. 2020. New taxa and new names 3: 97. Available at http://homepage.ntu.edu.tw/~yingshao/New%20taxa%20vol.%203.pdf ).

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 1966Adema F. 1966. A review of the herbaceous species of Polygala in Malesia (Polygalaceae). Blumea 14: 253-276.; Chandrabose & Nair 1981Chandrabose M. & Nair N.C. 1981. The genus Polygala L. (Polygalaceae) in Andhra Pradesh, Kerala, and Tamil Nadu (South India). Proceedings of Indian Academy of Science (Plant Sciences) 90: 107-127.; Banerjee 1993Banerjee R.N. 1993. Polygalaceae. In Sharma B.D. & Balakrishnan N.P. (ed.), Flora of India, vol. 1: 451-493. Botanical Survey of India, Kolkata.; Banerjee & Balakrishnan 2005Banerjee R.N. & Balakrishnan N.P. 2005. Polygalaceae. In Daniel P. (ed.), The flora of Kerala, vol. 1: 287-306. Botanical Survey of India, Kolkata. ; Chen & al. 2008Chen S.-K., Ma H.-Y. & Parnell J.A.N. 2008. Polygala. In Wu A.-Y., Raven P.H. & Hong D.Y. (eds.), Flora of China, vol. 11: 141-158. Science Press, Beijing and Missouri Botanical Garden Press, St. Louis. ; Ranjan 2009Ranjan S.R.K.U.N.D.U. 2009. A synopsis of Polygalaceae in Indian Subcontinent: Its distribution and endemism. Acta Botanica Venezuelica 32: 63-77.; Kerrigan 2008Kerrigan R.A. 2008. A taxonomic revision of Polygala L. in northern Australia. Thesis, James Cook University, Australia. , 2012Kerrigan R.A. 2012. A treatment for Polygala of northern Australia. Australian Systematic Botany 25: 83-137.; Yang & Chen 2013Yang A.T.Y & Chen C.F. 2013. A revision of the genus Polygala L. (Polygalaceae) in Taiwan. Taiwania 58: 156-162. ; Dönmez & Aydin 2018Dönmez A.A. & Aydin Z.U. 2018. Polygala azizsancarii (Polygalaceae), a new species from Mardin Province, SE Turkey. Phytotaxa 340: 255-262. ; Pastore 2018aPastore J.F.B. 2018a. Polygala veadeiroensis (Polygalaceae), a new species of Polygala endemic to Chapada dos Veadeiros, Goiás, Brazil. Kew Bulletin 73: 37., 2018bPastore J.F.B. 2018b. A new species and new combination in Polygala sect. Timutua series Timoutoideae from Brazil. Kew Bulletin 73: 51.; Pastore & al. 2019Pastore J.F.B., Abbott J.R., Neubig K.M., van den Berg C., Mota M., Cabral A. & Whitten W.M. 2019. Phylogeny and biogeography of Polygala (Polygalaceae). Taxon 68: 673-691.; Sarvi & al. 2020Sarvi A., Beygom F.M. & Shahi S.R. 2020. Polygala mazandaranica (Polygalaceae), a new species from Mazandaran province, North Iran. Phytologia Balcanica 26: 461-469.; Ying 2020Ying S. 2020. New taxa and new names 3: 97. Available at http://homepage.ntu.edu.tw/~yingshao/New%20taxa%20vol.%203.pdf ; Pastore & al. 2021aPastore J.F.B., Motta M., Amano E. & Agustina M. 2021a. Disentangling Polygala obovata complex (Polygalaceae), with a description of three new species for Brazil. Systematic Botany 46: 985-997., 2021bPastore J.F.B., Flaviano S.S., Pivari M.O.D., Anastacio A.C.S.A. & Amano E. 2021b. Polygala petricola (Polygalaceae), a new species from Brazil. Edinburgh Journal of Botany 78: 356. ; Pastore & Antar 2021Pastore J.F.B. & Antar G.M. 2021. Two new endangered species of Polygala series Trichospermae (Polygalaceae), endemic to the Cerrado domain, Tocantins State, Brazil. European Journal of Taxonomy 762: 133-148.; Sarvi & al. 2021Sarvi A., Beygom F.M. & Shahi S.R. 2021. Polygala guilanica (Polygalaceae), a new species from Guilan Province, North Iran. Phytotaxa 513: 141-151.; Pastore 2022Pastore J.F.B. 2022. Revision of the ‘Polygala herbiola group’ (Polygalaceae): a new species and a new variety. Kew Bulletin 77: 221-232.) 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.

MATERIALS AND METHODS

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)Simpson M.G. 2006. Plant Systematics. Elsevier Academic Press, London., Kerrigan (2008Kerrigan R.A. 2008. A taxonomic revision of Polygala L. in northern Australia. Thesis, James Cook University, Australia. , 2012Kerrigan R.A. 2012. A treatment for Polygala of northern Australia. Australian Systematic Botany 25: 83-137.), and Pastore (2018aPastore J.F.B. 2018a. Polygala veadeiroensis (Polygalaceae), a new species of Polygala endemic to Chapada dos Veadeiros, Goiás, Brazil. Kew Bulletin 73: 37., 2018bPastore J.F.B. 2018b. A new species and new combination in Polygala sect. Timutua series Timoutoideae from Brazil. Kew Bulletin 73: 51.). Herbarium sheets were prepared by conventional methods (Bridson & Forman 1991Bridson D.M. & Forman L. 1991. The Herbarium Handbook. Royal Botanic Gardens, Kew.). 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).

RESULTS AND DISCUSSION

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. 1-3Fig. 1, 2, 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 2022IUCN 2022. Guidelines for using the IUCN Red list Categories and Criteria. Version 15. Prepared by the Standards and Petitions Subcommittee of the IUCN Species Survival Commission.).

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 afterBanerjee & Balakrishnan 2005Banerjee R.N. & Balakrishnan N.P. 2005. Polygalaceae. In Daniel P. (ed.), The flora of Kerala, vol. 1: 287-306. Botanical Survey of India, Kolkata. )