INTRODUCTION
⌅Orobanchaceae, commonly called ‘broomrapes’, is the largest parasitic angiosperm family with morphologically diverse herbaceous plants (Young & al. 1999Young N.D., Steiner K.E. & Depamphilis C.W. 1999. The evolution of parasitism in Scrophulariaceae/Orobanchaceae: plastid gene sequences refute an evolutionary transition series. Annals of the Missouri Botanical Garden 86: 876-893.). Most of the species are facultative or obligate root parasites which may be photosynthetic (hemiparasites) or totally depend on host plants (holoparasites). Parasopubia H.-P.Hofm. & Eb.Fisch., a genus of Orobanchaceae recently segregated from Sopubia Ham. ex D.Don (Hofmann & Fischer 2004Hofmann H.-P. & Fischer E. 2004. Generic delimitation of Sopubia Buch.-Ham. (Scrophulariaceae), revision of Petitmenginia bonati and description of the new Asian genus Parasopubia. Botanische Jahrbücher für Systematik, Pflanzengeschichte und Pflanzengeographie 125: 341-375.), is characterized by slightly zygomorphic flowers, corolla tube much longer than lobes and acuminate reduced thecae. The genus comprises four taxa, including the new species here described, distributed in South East Asia. Parasopubia bonatii H.-P.Hofm. & Eb.Fisch. is distributed in Cambodia, Laos, Vietnam, Thailand and China (Bonati 1927Bonati G. 1927. Scrophulariacées. In: Lecomte H. & Humbert H. (eds.), Flore Générale de I’Indo-Chine 4: 341-461. Messon et Cie Éditeurs, Paris.) while P. delphinifolia (L.) H.-P.Hofm. & Eb.Fisch., P. hofmannii Pradeep & Pramod var. hofmannii and P. hofmannii var. albiflora Pradeep & Pramod are found in India (Pradeep & Pramod 2013Pradeep A.K & Pramod C. 2013. Parasopubia hofmannii Pradeep & Pramod and Parasopubia hofmannii var. albiflora Pradeep & Pramod (Orobanchaceae), two new taxa from India. Candollea 68: 115-122.) (Fig. 1). Members of this genus are usually seen in grasslands, wet rocks, cultivated lands, marshy areas, lateritic hillocks and moist deciduous forests.
During our field work in Idukki district, Kerala, an interesting species of Parasopubia was collected from Mathikettan Shola National Park (MSNP). After careful comparison of Parasopubia specimens and consulting relevant literature, the authors found that it was quite distinct from other taxa in the genus and hence is described here as a new species.
MATERIALS AND METHODS
⌅Fresh specimens were collected from Mathikettan Shola National Park of Idukki district. Protologues and relevant literature (Bonati 1927Bonati G. 1927. Scrophulariacées. In: Lecomte H. & Humbert H. (eds.), Flore Générale de I’Indo-Chine 4: 341-461. Messon et Cie Éditeurs, Paris.; Hofmann & Fischer 2004Hofmann H.-P. & Fischer E. 2004. Generic delimitation of Sopubia Buch.-Ham. (Scrophulariaceae), revision of Petitmenginia bonati and description of the new Asian genus Parasopubia. Botanische Jahrbücher für Systematik, Pflanzengeschichte und Pflanzengeographie 125: 341-375.; Pradeep & Pramod 2013Pradeep A.K & Pramod C. 2013. Parasopubia hofmannii Pradeep & Pramod and Parasopubia hofmannii var. albiflora Pradeep & Pramod (Orobanchaceae), two new taxa from India. Candollea 68: 115-122.) were examined for confirming the identity of the specimens and detailed descriptions were made. The following virtual herbaria were also searched for confirming the identity of the specimens: K, M and S (acronyms according to Thiers 2021Thiers B.M. 2021 [continuously updated]. Index Herbariorum: A global directory of public herbaria and associated staff. New York Botanical Garden’s Virtual Herbarium. Website: http://sweetgum.nybg.org/ih/ [accessed: 18 Feb. 2021]., continuously updated). Herbarium sheets were prepared as per Bridson and Forman (1991)Bridson D.M. & Forman L. 1991. The Herbarium Handbook. Royal Botanic Gardens, Kew.. Conservation assessment was done using IUCN standards and petition committee criteria (IUCN 2019IUCN 2019. The IUCN Red List of Threatened Species. Version 2019-2. IUCN Species Survival Commission. Gland, Switzerland.). The photographs of floral parts were taken with a Stemi 508 Stereomicroscope attached to an Axiocam 105 colour Camera (Zeiss, Germany). The ultra-morphological analysis of seeds was done using DM6 B Phase Contrast Microscope fitted with a DFC450 Camera (Leica, Switzerland) and Gemini 300 Scanning Electron Microscope (Zeiss, Germany).
RESULTS AND DISCUSSION
⌅Taxonomic treatment
⌅Parasopubia raghavendrae Divya & Nampy, sp. nov. Type: India, Kerala: Idukki district, Mathikettan Shola National Park (MSNP), Sivanpara, ± 1610 m, 11 Dec. 2016, D.K. Venugopal & S. Nampy 151405 (holotype: CALI!; isotypes: CALI!, CAL!). Fig. 2.
Diagnosis.-It is similar to Parasopubia delphinifolia and P. hofmannii var. hofmannii but can be easily distinguished by the calyx with tube exceeding lobes (4-4.5 mm against 3.5-3.8 mm long), the glandular hairy staminal filaments and stomium, the oblong capsules and seeds in contrast with the calyx tube less long than calyx lobes (2-2.5 mm against 4 mm long in P. hofmannii var. hofmannii; 4 mm against 7 mm long in P. delphinifolia), and glabrous staminal filaments and stomium. The capsules are elliptic and the seeds obovate in P. delphinifolia while obovoid and obovate, respectively in P. hofmannii var. hofmannii. The testa is uniformly ribbed and parallely reticulate with wide testa cells in P. raghavendrae while non-uniformly ribbed and obliquely reticulate in P. hofmannii var. hofmannii and P. delphinifolia. However, the testa cells are narrow in the former and wide in the latter.
Annual herbs up to 50 cm tall. Stems terete at base, 4-angular above, densely branched (branches 6-30), green. Leaves opposite, 2-5 cm long, sessile; lower leaves 5-7 segmented; segments linear-lanceolate to filiform; upper leaves entire; midrib prominent abaxially, strigose on margins, green. Flowers axillary, solitary, bisexual, zygomorphic, 1-1.5 × 0.5-1 cm. Pedicels 1-1.5 cm long, tomentose, green; bracteoles 2, linear, 2-2.3 × 0.5-1 mm, glabrous, green. Calyx 5-lobed, persistent in fruit; tube 4-4.5 mm long, longer than lobes, glabrous; lobes linear, 3.5-3.8 × 1-1.1 mm, acute at apex, glabrous, green. Corolla campanulate, puberulent on outer surface, glabrous on inner surface, pink; tube 6.8-7 × 1-1.5 mm; lobes nearly sub-rotund, 3-3.2 × 4-4.1 mm. Stamens 4, unequal, inserted on corolla tube; filaments deep pink, 2 longer (6 mm long), 2 shorter (5 mm long), glandular hairy; anthers 2, pendent, thecae pale brown, one fertile and one sterile, unequal; fertile thecae 2 × 1 mm; sterile thecae 1 × 1 mm; stomium hairy, opening whole length. Ovary superior, 1 × 1 mm, ellipsoid, 2-celled, glabrous, green; ovules many in each cell; style slender, 8-8.2 × 1-1.1 mm, puberulent distally, pale pink; stigma globose, glabrous. Capsules oblong, erect, 5-5.3 mm long, glabrous; – portion enclosed in calyx tube; fruiting calyx lobes erect. Seeds numerous, oblong, 0.57 mm long, brown; testa uniformly ribbed and parallely reticulate with wide testa cells.
Distribution and habitat.-The new species is hitherto known only from the type locality. It grows in wet humus-rich rock crevices at an elevation of c. 1610 m along with Murdannia satheeshiana Joby, Nisha & Unni, Cyanotis sp. (both Commelinaceae), Eriocaulon sp. (Eriocaulaceae), Polycarpaea corymbosa (L.) Lam. (Caryophyllaceae), etc.
Phenology.-Flowering and fruiting from early December to late January.
Etymology. -The new species is named in honour of Dr. R. Raghavendra Rao, for his contributions in Indian botany.
Provisional conservation status.-The new species is currently known only from the type locality in the Mathikettan Shola National Park. Two populations with approximately 15 mature individuals were observed in two successive years (2017-2019) and the populations were separated by a distance of around 300 m. There is no possible threat as the area falls under a National Park. On the basis of available data, this species is categorized provisionally as Critically Endangered (CR) (by considering area of occupancy < 10 km2 [B2]; number of mature individuals in each population ≤ 50 [C2 a]; very small or restricted population with number of mature individuals < 50 [D]) as per IUCN Red List Categories and Criteria (IUCN, 2019IUCN 2019. The IUCN Red List of Threatened Species. Version 2019-2. IUCN Species Survival Commission. Gland, Switzerland.).
Notes. -It is worth mentioning that Parasopubia raghavendrae shares the habit and hairiness of corolla lobes with other taxa of Parasopubia in India. Parasopubia raghavendrae is peculiar by its hairy staminal filaments and stomium, uniformly ribbed testa and parallely reticulate wide testa cells. It grows in wet, humus rich non-lateritic rocks, while P. hofmannii var. hofmannii grows in lateritic rocks and P. delphinifolia in almost all habitats (in grasslands, cultivated lands, marshes, lateritic rocks and non-lateritic rocks, etc.). The flowering period of the three taxa are: P. delphinifolia from August to February, P. hofmannii var. hofmannii from July to September while P. raghavendrae from December to January. A comparison of diagnostic characters between P. delphinifolia, P. hofmanni var. hofmannii and P. raghavendrae is given in Table 1.
| Character | P. delphinifolia | P. hofmannii var. hofmannii | P. raghavendrae |
|---|---|---|---|
| Calyx tube length |
|
|
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| Calyx lobes length, shape |
|
|
|
| Staminal filaments indument and length | |||
| Fertile and sterile thecae |
|
|
|
| Stomium | |||
| Fruiting calyx lobes |
|
|
|
| Capsules | |||
| Seeds |
Key to the species of genus Parasopubia including the new species
| 1. | Plants stout; calyx lobes broadly triangular, without linear extension | P. bonatii |
| - | Plants slender; calyx lobes linear or lanceolate, with linear extension | 2 |
| 2. | Fruiting calyx lobes erect | 3 |
| - | Fruiting calyx lobes divergent | 4 |
| 3. | Calyx with tube shorter than lobes; calyx lobes lanceolate; stomium opening from apex; capsules elliptic, slightly pubescent | P. delphinifolia |
| - | Calyx with tube longer than lobes; calyx lobes linear; stomium opening whole length; capsules oblong, glabrous | P. raghavendrae |
| 4. | Corolla pale pink; plant parts often purplish; testa cells narrow | P. hofmannii var . hofmannii |
| - | Corolla white; plant parts without purplish tinge; testa cells wide | P. hofmannii var. albiflora |
Additional specimens examined.-Parasopubia delphinifolia. INDIA. Kerala: Malappuram district, Kozhippara, 21 Oct. 2009, A.K. Pradeep 90072 (CALI 152574); C U Campus, 22 Nov. 1989, Ushakumari V.N. 4878 (CALI 152663); ibid., 02 Sep. 1990, Solly George 3238 (CALI 152665). Tamil Nadu: Coimbatore district, Mount Stouert, 27 Oct. 1961, J. Joseph 13377 (MH 00125774, MH 00125773); Dharmapuri district, Dhoddikere, 22 Dec. 1990, T. Ravishankar 95524 (MH 00125763, MH 00125762). s.d., s.coll., s.n. (M 0188641 digital image); s.loc., 1 Jan. 1777, Johann G. Konig s.n. (S 09-26708 digital image); s.loc., 1831, N. Wallich 3890 (K 000999981 digital image).-Parasopubia hofmanni var. hofmannii. INDIA. Kerala: Kannur district, Madayippara, 27 Nov. 2011, Pramod CU 151405 (holotype CALI); ibid., 11 Sep. 2009, Pramod CU 123592 (CALI); ibid., 01 Aug. 2010, Pramod CU 126510 (CALI); ibid., 20 Aug. 2010, Pramod CU 126555 (CALI).