NORDIC JOURNAL OF BOTANY Research A new rheophytic species of Pavetta (Rubiaceae) from Assam, northeast India Jatindra Sarma, Hussain Ahmed Barbhuiya and Santanu Dey J. Sarma – Development, Research, Education and Working Plans, Assam Forest Dept, Aranya Bhawan, Panjabari, Guwahati, Assam, India. – H. A. Barbhuiya (http://orcid.org/0000-0002-7462-1286) (hahmed@barc.gov.in), Landscape and Cosmetic Maintenance Section, Architectural and Structural Engineering Division, Bhabha Atomic Research Centre, Trombay, Mumbai, Maharashtra, India. – S. Dey, Dept of Botany, Nagaland Univ., Lumami, Nagaland, India. Nordic Journal of Botany 2019: e02076 doi: 10.1111/njb.02076 Subject Editor: Torbjörn Tyler Editor-in-Chief: Torbjörn Tyler Accepted 26 September 2018 A new species, Pavetta puffii, is described and illustrated from Assam, northeast India. The taxonomic relationships of the new species with the hitherto known species of genus Pavetta are examined and discussed. Keywords: Rubiaceae, Pavetta, Rheophyte, West Karbi Anglong, Assam, Endemic Introduction Pavetta L. is the largest genus of the tribe Pavetteae, which belongs to the subfamily Ixoroideae of Rubiaceae (coffee family). Pavetta comprises ca 360 species (De Block et al. 2015) and has a paleotropical distribution, i.e. widespread in tropical Asia, Australia, Pacific islands and Africa, but is absent from Madagascar (Chen and Taylor 2011). On the Indian subcontinent, the genus is represented by 25 species and 8 varieties (Rout and Deb 1999). Pavetta was thoroughly studied by Bremekamp (1934, 1939a, b), who recognized three subgenera viz. Dizygoon, Baconia and Eupavetta, which are well defined morphologically by their flowers and fruits, and also by their pollen types (De Block and Robbrecht 1998). The species of Pavetta are easily recognised by their 4-merous flowers, stigmatic lobes fused over most of their length, single ovule per locule, hemispherical seeds with a large adaxial hilar cavity and presence of bacterial leaf galls (Lemaire et al. 2012, De Block et al. 2015). The present species belongs to the section Pavettaster Bremek. of subgenus Eupavetta Bremek. (Bremekamp 1934), it shows close resemblances to P. agrostiphylla Bremek. but differs in various aspects. The new species shows typical characteristics of a rheopyte. Rheophytes are the plant species which are confined to the beds of swift-running streams and rivers and grow there up to flood-level, but not beyond the reach of regularly occurring flash floods. Rheophytic land plants either can be herbs or shrubs. Shrubby rheophytes usually have their roots matted on rocks, shows sympodial branching habit and bears shortly petioled, glabrous, narrow leaves with entire margins (van Steenis 1981, 1987). –––––––––––––––––––––––––––––––––––––––– © 2018 The Authors. Nordic Journal of Botany © 2018 Nordic Society Oikos www.nordicjbotany.org 1 Material and methods During field explorations (2016–2018) at Koka, Panimur, Amreng and Zirikindeng regions of the West Karbi Anglong District of Assam the senior author found a shrub growing in rock crevices at the edges of Kopili riverbed near Koka. Upon critical examination of both floral and vegetative morphology the collected plant material turned out to belong to a new species of Pavetta, which is described and illustrated here. Pavetta puffii Barbhuiya, J.Sarma & S.Dey sp. nov. (Fig. 1–2) A species differing from P. agrostiphylla Bremek. in having shortly and obtusely acuminate leaf apices (never caudate), strongly congested capitate inflorescences with more numerous flowers per inflorescence (usually 30–70 vs 8–22 flowers in P. agrostiphylla), smaller (0.3–0.5 mm vs 1.0–1.2 mm in P. agrostiphylla), broadly triangular and unkeeled calyx lobes (vs narrowly triangular, recurved and keeled calyx lobes in P. agrostiphylla), shorter corolla tubes (≤ 14.7 mm vs 20–22 mm in P. agrostiphylla) and corolla lobes (< 5 mm vs 10–12 mm in P. agrostiphylla), glabrous filaments (vs puberulous filaments in P. agrostiphylla) and a moderately clavate stigma (vs more or less filiform stigma in P. agrostiphylla). Type: India. Assam, West Karbi Anglong District, Panimur, Koka, on the edges of Kopili riverbed, 25°43¢03.73²N, 92°49¢22.48²E, ca 102 m a.s.l., 7 May 2017, J. Sarma s.n. (holotype: HBARC-00006398, isotypes: ASSAM, CAL). Etymology The species is named in honour of the late Prof. Dr Christian Puff (1949–2013), an Austrian botanist who devoted his life to the study of the Rubiaceae family and, in later years, focused his work on the ‘Flora of Thailand’ project. Prior to his death, he made a field visit to India in search of Rubiaceae plants especially in Assam. During his visit, he spent time (from 8 to 22 August 2013) with the first and last author. Description A rheopytic shrub, 60–80 cm tall. Leaf blades linear lanceolate, 3.0–15.5 × 0.4–1.5 cm; both surfaces glabrous; margins entire, revolute; apex shortly and obtusely acuminate; lateral nerves not prominent, brochidodromous, usually 3–6 on each side of the midrib, alternate to sub-opposite; domatia absent; bacterial leaf galls present in between the midrib and loop of lateral nerves, usually along the lateral nerves, rarely on the midrib, depressed above, more prominent on lower surface, up to 15 in older leaves but apparently absent in youngest ones, mostly circular to elliptical, 0.6– 1.3 mm long, with 1 or 2 pores at adaxial surface; petiole 0.6–1.5 cm long, glabrous. Stipules interpetiolar, united at the base; sheaths broadly triangular, 1.7–3.3 × 2.4–3.7 mm, glabrous outside, with colleters inside the stipular sheaths; apex cuspidate. Inflorescence terminal, sessile, subcapitate corymbose-cymes, with 30–70 flowers per inflorescence. Bract membranous, broadly triangular, ca 5.4 × 9.9 mm, united at base, glabrous outside, occasionally sparsely pubescent within, cuspidate at apex. Flowers white, pedicillate. Pedicel 3.5–4.5 mm long, glabrous, cylindrical, 0.5–0.8 mm in diameter. Calyx tube slightly campanulate, 0.6–1.0 mm long and 1.2–1.3 mm in diameter, glabrous outside but with trichomes inside; calyx teeth broadly triangular, 0.3–0.5 × 0.3–0.6 mm, unkeeled, sparsely hairy at the margins. Corolla tube 11.3–14.7 mm long, 1.1–1.5 mm in diameter, glabrous outside, their upper half sparsely pubescent within; corolla lobes oblong-lanceolate, 4.6–4.9 × 1.7–2.0 mm, glabrous, acute at apex. Anthers sub-basifixed, 3.7–4.1 × 0.6–1.0 mm; filaments short, glabrous, 0.6–0.7 mm long and ca 0.2 mm wide. Ovary glabrous, 1.1–1.2 × 1.0–1.3 mm; style 27–29 mm long, slender, glabrous; stigma slightly clavate, with hairy ridges, 1.0–1.5 mm long. Fruit sub-globose or rarely didymous, 6.4–6.7 × 5.6–6.0 mm, greenish while young, turning blackish-green when mature; fruiting pedicel gradually dilated distally, 6.0–7.8 mm long, 0.6–1.6 mm in diameter. Seed 1 (–2), more or less rounded, 4.5–6.0 mm in diameter. Figure 1. Pavetta puffii sp. nov. (A) inflorescence, (B) infructescence. Photographs by J. Sarma. 2 Figure 2. Pavetta puffii sp. nov. (A) leaves, (B)–(D) stipules, (E)–(F) inflorescence, (G) a portion of the cyme, (H) lower portion of the inflorescence showing bracts, (I) a flower bud, (J) a flower, (K) a flower with opened corolla tube, (L) lower portion of the flower showing calyx and ovary, (M) L.S. through calyx tube and ovary, (N) a magnified view of calyx lobe showing hairy margins, (O) an opened corolla tube with corolla lobe, (P) magnified view of corolla lobes, (Q) inner surface of corolla tube showing hairs, (R ) stamens, (S) carpel with calyx tube and pedicel, (T) stigma, (U) fruits, (V) seeds. (N) = not to scale. Photographs (A)–(V) by H. A. Barbhuiya, all from spirit material, J. Sarma s.n. (HBARC). Phenology Flowering and fruiting occurs from April to May. Distribution Only known from the type locality, Koka, Panimur, West Karbi Anglong District, Assam, India (Fig. 4). Habitat and ecology Pavetta puffii grows in rock crevices along the riverbed, preferably in shady places at 86–102 m a.s.l. The species is adapted to the rheophytic environment and prefer to grow near fast flowing water. The leaves of P. puffii shows typical characteristics of a rheophyte such as shortly petiolated glabrous leaves with narrow leaf blades having entire margins. The other associated rheophytes occurring in the type locality were Syzygium cyanophyllum (P.C.Kanjilal & D.Das) Raizada, S. polypetalum (Wall.) Merr. & L.M.Perry, Ixora yunnanensis Hutch., Carissa sp., Tarenna pumila (Hook.f.) Merr., Eriobotrya angustissima Hook.f., Millettia piscidia (Roxb.) Wight, Melastoma malabathricum L. etc. Conservation status Pavetta puffii is only known from the type gathering; hence, its conservation status remains ‘Data Deficient’ (DD) under the IUCN conservation status (IUCN 2012). 3 Figure 3. Pavetta agrostiphylla Bremek. (A) leaves, (B) inflorescence, (C) flowers, (D) side view of flowers showing recurved calyx lobes, corolla tubes and corolla lobes. Photographs by Bushana Kalhara. Figure 4. Distribution map of Pavetta puffii sp. nov., P. agrostiphylla and P. subcapitata. Map created with SimpleMappr, < www. simplemappr.net > (Shorthouse 2010). 4 Table 1. Detailed comparison between Pavetta puffii, P. agrostiphylla and P. subcapitata. Characters Plant height (m) Leaf P. puffii sp. nov. size (cm) shape 0.6–0.8 3.0–15.5 × 0.4–1.5 linear lanceolate not known 4.5–20.0 × 0.5–3.0 linear or linear lanceolate surface glabrous glabrous apex domatia obtusely acuminate absent caudate acuminate absent bacterial leaf galls 0–15 per leaf, usually along secondary nerves, circular to elliptical, 0.6–1.3 mm long 3–6 few, on secondary or more finer nerves, circular, 0.5–1.0 mm in diam. 7–11 lateral nerves on each side of midrib Petiole (cm) 0.6–1.5, glabrous Stipules Inflorescence Peduncle Bract Flowers Pedicel Calyx tube lobes Corolla tube lobes Androecium Gynoecium anthers filament ovary style stigma Fruit Seeds Flowering time Distributions P. agrostiphylla (after Bremekamp 1934, Rout and Deb 1999) P. subcapitata (after Rout and Deb 1999) 2.0–4.5 6.3–28.5 × 1.5–7.5 elliptic, elliptic-oblong, lanceolate, obovate or oblanceolate pubescent or puberulous beneath acuminate or caudate present in secondary nerve axils many, on secondary or tertiary nerves, circular, elliptic or oblong, 0.5–3.0 mm long 7–12 0.4–2.0, glabrous 0.5–2.8, puberulous or pubescent broadly triangular, united at base, triangular, cuspidate at apex, broadly triangular, cuspidate shortly cuspidate at apex, 1.7–3.3 ca 6 × 4–5 mm, sparsely at apex, 4–6 × 3–5 mm, × 2.4–3.7 mm, glabrous outside pubescent outside with pubescent outside with with colleters inside colleters and trichomes colleters and trichomes inside inside terminal on main stem or on lateral terminal, rarely axillary, terminal, sessile or subsessile, branches, sessile, subcapitate sessile to pedunculate, subcapitate cymes, corymbose cyme, glabrous corymbose cymes pubescent not distinct 0–3 cm long, glabrous 0–4 mm long, pubescent broadly triangular, ca 5.4 × 9.9 mm, triangular, 3–4 × 3–4 mm, broadly triangular, 3–5 × glabrous outside, occasionally 1–3 mm, pubescent outside, sparsely pubescent outside, pubescent within, apex cuspidate glabrous within glabrous within, apex cuspidate pedicillate, 30–70 per inflorescence pedicillate, 8–22 per sessile to subsessile, 20–62 inflorescence per inflorescence 3.5–4.5 mm long, glabrous 3–7 mm long, glabrous 0–1.5 mm long 0.6–1.0 × 1.2–1.3 mm, glabrous ca 1.2 × 2.0 mm, broader ca 1.0 × 1.5 mm, pubescent outside with trichomes inside above, glabrous outside, glabrous within broadly triangular, straight, 0.3–0.5 × narrowly triangular, recurved, triangular, ca 0.3 × 0.2 mm, 1.0–1.2 × 0.6–0.8 mm, 0.3–0.6 mm, unkeeled, apex acute, subacute at apex, pubescent keeled at back, apex acute, sparsely pubescent on the margins outside, glabrous within sparsely pubescent on the margins 11.3–14.7 × 1.1–1.5 mm, glabrous 20–22 × 1.5–3.0 mm, 16–22 × ca 1 mm, glabrous outside, upper half sparsely glabrous outside, sparsely outside, pilose within pubescent within pubescent within oblong-lanceolate, 4.6–4.9 × 1.7–2.0 oblong,10–12 × 2.5–3.0 mm, oblong or obovate, 5.0–6.5 × mm, glabrous, apex acute glabrous, apex acute 2.0–3.0 mm, apex obtuse, rounded or mucronate 3.7–4.1 mm 7–8 mm ca 5 mm 0.6–0.7 mm, glabrous ca 2 mm, puberulos ca 0.5 mm, glabrous 1.1–1.2 × 1.0–1.3 mm ca 1 × 1 mm ca 0.8 × 0.8 mm 27–29 mm long, slender, glabrous 48–65 mm long, stout, lower 35–40 mm long, slender, half glabrous, upper half lower half glabrous, upper puberulous half puberulous slightly clavate, ca 1 mm long, filiform, ca 2 mm long, fusiform, ca 3 mm long, puberulous puberulous pubescent 7–8 mm in across, pubescent 6.4–6.7 × 5.6–6.0 mm, glabrous 5–6 × 5–8 mm, glabrous 4.5–6.0 mm in diam. ca 4 mm in diam. ca 6 mm in diam. Apr–May Mar–Aug Apr–Sept endemic to Assam, India endemic to Sri Lanka NE India and Bangladesh 5 Similar species Pavetta puffii shows superficial similarity with P. agrostiphylla in having narrow-lanceolate leaves. But, P. agrostiphylla differs from the newly described species by the long-caudate acuminate leaf apices, the less compact inflorescences with 8–22 flowers (vs capitate inflorescences with 30–70 flowers in P. puffii), the larger size of flowers (corolla tube 20–22 mm long vs 11.3–14.7 mm long in P. puffii, corolla lobes 10–12 mm long vs 4.6–4.9 mm in P. puffii), the 1.0–1.2 mm long, oblong, recurved and keeled calyx lobes (vs 0.3–0.5 mm long, broadly triangular and unkeeled calyx lobes in P. puffii), the puberulous filaments (vs glabrous filaments in P. puffii) and the filiform stigma (vs moderately clavate stigma in P. puffii) (Fig. 3). Furthermore, P. agrostiphylla is endemic to Sri Lanka (Ridsdale 1998), which is far away and isolated by a large sea barrier (Fig. 4) from the type locality of P. puffii. Pavetta puffii also shows some affinity with P. subcapitata Hook.f. (a broadly sympatric species) because of the capitate inflorescences, but differs by the narrowly lanceolate, glabrous leaves without domatia (vs 1.5–7.5 cm wide leaves in P. subcapitata), the pedicellate flowers (vs sessile flowers in P. subcapitata) and the shorter, 27–29 mm long, glabrous styles (vs 35–40 mm long, puberulous styles in P. subcapitata). A detailed comparison between the discussed species is provided in Table 1. Acknowledgements – We are thankful to the Assam Forest Dept for allowing us to use their resources in extensive field exploration works especially in remote areas. We extend our sincere thanks to Karbi Anglong Autonomous Council Authority and Hamren Forest Division for providing logistic support during field tours. We acknowledge our heartiest thanks to officers and staff members of Southern Range Kheroni, Hamren Forest Division for their continuous assistance in frequent field explorations. Finally, yet importantly, we are indebted to Bushana Kalhara, Colombo district, Western Province, Sri Lanka for providing the photographs of P. agrostiphylla. 6 References Bremekamp, C. E. B. 1934. A monograph of the genus Pavetta L. – Repert. Spec. Nov. Regni Veg. 37: 1–208. Bremekamp, C. E. B. 1939a. A monograph of the genus Pavetta L.: additions and emendations. – Repert. Spec. Nov. Regni Veg. 47: 12–28. Bremekamp, C. E. B. 1939b. A monograph of the genus Pavetta L.: additions and emendations II. – Repert. Spec. Nov. Reg. Veg. 47: 81–98. De Block, P. and Robbrecht, E. 1998. Pollen morphology of the Pavetteae (Rubiaceae, Ixoroideae) and its taxonomic significance. – Grana 37: 260–275. De Block, P. et al. 2015. 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