Journal of Threatened Taxa | www.threatenedtaxa.org | 26 March 2021 | 13(3): 18054–18058

 

ISSN 0974-7907 (Online) | ISSN 0974-7893 (Print) 

https://doi.org/10.11609/jott.4801.13.3.18054-18058

#4801 | Received 07 January 2019 | Final received 17 November 2020 | Finally accepted 29 January 2021

 

 

Revisiting the taxonomy of Strobilanthes lawsonii and S. pushpangadanii (Acanthaceae), two endemic taxa of Western Ghats, India

 

Blessy Cherian 1, K.M. Prabhukumar 2, R. Jagadeesan 3, V.V. Naveen Kumar 4 & Indira Balachandran 5

 

1–5 Centre for Medicinal Plants Research (CMPR), Arya Vaidya Sala, Kottakkal, Malappuram, Kerala 676503, India.

2 Present address: Plant Diversity, Systematics & Herbarium Division, CSIR-National Botanical Research Institute, Rana Pratap Marg, Lucknow, Uttat Pradesh 226001, India.

1 blessysmiles@gmail.com, 2 prabhu.krishna@nbri.res.in (corresponding author), 3 vishnuviru22@gmail.com, 4 naveenkumar2389@gmail.com, 5 indirapa@hotmail.com

 

 

 

Editor: N.P. Balakrishnan, Coimbatore, Tamil Nadu, India.          Date of publication: 26 March 2021 (online & print)

 

Citation: Cherian, B., K.M. Prabhukumar, R. Jagadeesan, V.V.N. Kumar & I. Balachandran (2021). Revisiting the taxonomy of Strobilanthes lawsonii and S. pushpangadanii (Acanthaceae), two endemic taxa of Western Ghats, India. Journal of Threatened Taxa 13(3): 18054–18058. https://doi.org/10.11609/jott.4801.13.3.18054-18058

 

Copyright: © Cherian et al. 2021. Creative Commons Attribution 4.0 International License.  JoTT allows unrestricted use, reproduction, and distribution of this article in any medium by providing adequate credit to the author(s) and the source of publication.

 

Funding: None.

 

Competing interests: The authors declare no competing interests.

 

Acknowledgements: The authors express sincere gratitude to authorities of Arya Vaidya Sala, Kottakkal for their support and Tata Trusts, Mumbai for financial assistance.  Thanks are also due to Dr. Mark Carine, The Natural History Museum, United Kingdom and Dr. E.S. Santhosh Kumar, JNTBGRI, Thiruvanathapuram for their comment on the identity S. gamblei and S. pushpangadanii respectively; Dr. Maya C. Nair, Govt. Victoria College, Palakkad, P.M. Binu Prakash, CMPR for their help in the field.  Department of Kerala Forest is also thankfully acknowledged for the permission granted to enter the forest.

 

 

 

Strobilanthes Blume (1826), the second largest genus in the family Acanthaceae Juss. (1789), consists of 400 species restricted to the hilly regions of tropical Asia (Wood 1998; Augustine 2018).  In India, it is represented by 160–170 species from the mountains of peninsular India and the Himalaya of northeastern and northwestern India.  In peninsular India, 65 taxa are recorded so far with many new recent additions (Gamble 1924; Venu 2006; Josekutty et al. 2016, 2017, 2018; Sasidharan et al. 2016; Augustine et al. 2017; Biju et al. 2017; Augustine 2018).  Clarke (1885) enumerated 146 species of Strobilanthes in the Flora of British India.  In southern India and Sri Lanka, the genus is represented by 65 species, of which most are endemics (Carine & Scotland 2002).

EIght years of explorations in the southern region of the Western Ghats has resulted in the documentation and collection of many endemic Strobilanthes species.  Among them, materials collected from Nelliyampathy forests (CMPR 8707, 9589) and Muthikulam forests (CMPR 9879) of Palakkad District, Kerala did not key out their identity exactly.  After detailed taxonomic studies with the perusal of relevant literature (Clarke 1885; Gamble 1924; Santhoshkumar et al. 2002; Venu & Daniel 2003; Carine et al. 2004; Venu 2006) revealed their identity as S. pushpangadanii E.S.S. Kumar et al. (2002: 73), S. gamblei Carine et al. (2004: 5), and S. lawsonii Gamble (1923: 374) respectively.

Since 1923, many subsequent researchers recorded the distribution of S. lawsonii from different localities of Kerala in their floristic reports (Ramachandarn & Nair 1980; Sasidharan 2004, 2013).  But our herbarium survey revealed that the materials so far identified as S. lawsonii are either S. gamblei or S. pushpangadanii.  Hence our present collection is a rediscovery of S. lawsonii after Gamble’s collection in 1884, after a lapse of 133 years.

Based on the evidence of the live collection of S. gamblei and S. pushpangadanii from Nelliyampathy forests of Palakkad, we reinstate S. pushpangadanii as a distinct species, with the most notable morphological differences from S. lawsonii (Table 1) being partially fused corolla lobes, exserted stamens, and glabrous style. The latter species, S. gamblei has been recently reinstated by Pradeep et al. (2020).

 

Strobilanthes lawsonii Gamble Bull. Misc. Inform. Kew 1923: 374. 1923. (Image 1, Figure 1)

Type: Tamil Nadu. Nilgiri Distr., 6000ft., Nov. 1883, Gamble 13387 (lectotype: K!)

=Phlebophyllum lawsonii (Gamble) Bremek., Verh. Acad. Wet. afd. Natuurk. Sect. 2, 41: 169. 1944.

Type: Same as S. lawsonii.

Erect shrubs.  Stem quadrangular with dense tawny coloured short simple hairs; young branches are similar to that of its main axis.  Leaves opposite-decussate, petiolate; petiole 2.3–3.8 cm long, pubescence as same as in stem.  Lamina 8.7–14.8 × 3.0–6.2 cm long, ovate, apex long acuminate, decurrent at base, margin entire, abaxial surface covered with dense tawny-coloured woolly indumentum, adaxial surface glabrous; venation reticulated; nerves 9–11 pairs, arcuate, parallel with invisible reticulations, prominent on both surfaces while less in adaxial surface comparatively.  Inflorescence spike, axillary and terminal, simple or branched, 1–3 branches, narrowly cylindrical, 26–70 × 3.5–5 mm, interrupted; peduncle 1.0–1.5 cm long, densely covered with tawny tomentose indumentum.  Bract single, 4.5–4.8 ×1.5–1.6 mm long, shorter than calyx, ovate, green, apex acuminate, margin entire, adaxial surface and margins with dense tawny woolly indumentum.  Bracteole 2, ca. 3.5mm long.  Flower 2–2.2 cm long, blue, covered with soft tawny hairs, sessile.  Calyx 5-lobed, unequal, 2 or 3 lobes are larger than the rest, 5.6–6.5 mm long, lobes lanceolate, acuminate or acute at apex, margin entire, adaxial surface covered with simple white delicate hairs, abaxial surface densely covered with tawny indumentum, similar to that of bract.  Corolla 5-lobed, equal, overlapping, 5.5-5.7 × ca. 0.5 mm long, ovate to broadly triangular, round or rarely acute at apex, margins almost entire, blue, throat campanulate, outer surface with soft tawny tomentose indumentum; tube 14.0–15.5 mm long, ventricose, outer surface with soft tawny hairs.  Stamens 2, equal, included; filaments 10–10.2 mm long, sparsely white hairs at base; anthers ca 1.8mm long, dithecous, dorsifixed.  Ovary 2-celled, superior, on a prominent disc, ca. 1.5mm long, oblong, glabrous. Style ca. 9.5mm long, pubescent; stigma 2.5mm long with sparsely white hairs.  Capsule 14–15 mm long, elliptic to narrowly obovate, glabrous.  Seeds 2.2–4.5 mm long.

Phenology: October–June.

Distribution and Ecology: Found in thick rainforest undergrowth and shades of open grassland in the evergreen forest.  The distribution of the species is strictly restricted to Tamil Nadu and Kerala (based on present collection) region of Western Ghats.

Additional specimens examined: India: Tamil Nadu. Nilgiri Dist., 6000ft. alt., xi.1883, Gamble, 13387 (BM!); Kerala. Palakkad District, Way to Elival Hills, 12.xi.2016, K.M. Prabhukumar & Binu Prakash, 9879 (CMPR!).

Reinstatement of S. pushpangadanii: In the protologue of Strobilanthes lawsonii, Gamble (1923) cites four materials, two from Sispara Ghat of Nilgiri Hills (Gamble 13387, 14252), one each from Thamracheri Ghat of Wayanad (Barber 5686) and Travancore hills (Bourdillon 42), however, the collection from Wayanad and Travancore hills is now considered representing two distinct species S. gamblei and S. pushpangadanii, respectively.

Carine et al. (2004) did an excellent revision of Strobilanthes kunthiana group in peninsular India with an understanding morphological comparison chart to distinguish the members among the group.  As per the protologue, hand drawing of flower on the type specimen (Gamble 13387; lectotype designated by Carine et al. (2004) and Isolectotype) and the present collection from Muthikulam Hills (9879), it is very clear that, S. lawsonii is distinct from S. gamblei and S. pushpangadanii by means of its equally divided corolla lobes.  But during the revisionary work of Strobilanthes in peninsular India, Venu (2006) synonymised S. gamblei and S. pushpangadanii under S. lawsonii with commenting “S. lawsonii looks very similar and stands between S. pushpangadanii and S. gamblei”.  But he completely ignored the most notable morphological feature of this group, fusion of corolla lobes, exsertion of stamens, and pubescence nature of style.  Based on the evidence of live collections and strong distinguishing characters between the taxa, status of S. pushpangadanii as a distinct species (Table 1 & Image 2). The latter species, S. gamblei (Image 3) has been recently reinstated by Pradeep et al. (2020).

Special notes: Augustine (2018) used a few photographs of the above discussed taxa provided by PKM with due acknowledgment.

 

Strobilanthes pushpangadanii E.S.S. Kumar, Jabbar & A.E.S. Khan, Rheedea 12: 73. 2002. (Image 2).

Type: India. Kerala. Thiruvanthapuram district, Mankayam hills, E.S.S. Kumar 14722 (Holotype: TBGT; Isotype: MH, CALI!)

Flowering & Fruiting: August–March.

Distribution and Ecology: Margins of evergreen forest and open grasslands in Kerala.  Carine (2004) noted that the distribution of the species is strictly restricted to Thiruvananthapuram and Idukki districts of southern Kerala, but our field surveys reveal that the occurrence of the species extends up to the Palakkad gap.

Additional specimens examined: 14722 (CALI!, Isotype), India, Kerala, Thiruvananthapuram District, Mankayam Hills, 800m, 20.x.1992, coll. E.S. Santosh Kumar; 14030 (CALI!), Idukki District, Vellimala, 1,700m, 20.viii.1994, coll. Augustine; 11157 (CALI!), Thiruvananthapuram District, Ponmudi, Barnes s.n (K!); 5936 (KFRI!), Chemingi, c. 900m, 24.i.1992, coll. Mohanan; Thrissur District, Sholayar, 25.x.1992, coll. N. Sasidharan; 9879 (CMPR), Palakkad District, Nelliyampathy, Minnampara, 12.xi.2016, coll. K.M. Prabhukumar & Binu Prakash.

 

 

Key to the species

 

1a.     Two partially fused corolla lobes, stamens exserted, style glabrous ...……………........................…..……… 2

1b.     Corolla lobes divided equally, stamens included, style pubescent …………...........................…… S. lawsonii

2a.     Leaves with up to 9cm long petiole and acuminate apex, margins entire, spikes uninterrupted, up to 6.5cm long, peduncle long, 2.3–6.5 cm long, corolla light pink ……...……………………..…………… S. gamblei

2b.     Leaves shortly petiolate up to 2cm long, apex short candidate-acuminate, margins denticulate or crenate-serrate, spikes interrupted, up to 10cm long, peduncle short, 1–1.5 cm long, corolla light pink with dark purple venation ………………..………………........ ……………..………. S. pushpangadanii

 

 

Table 1. Comparison of morphological features of Strobilanthes lawsonii, S. gamblei, and S. pushpangadanii

Character

S. gamblei

S. pushpangadanii

S. lawsonii

Young stem

quadrangular

cylindrical

quadrangular

Petiole length

3−9 cm

1.5−2 cm

2.3−3.8 cm

Leaf size

5.5–15 × 2–6 cm

3.2–12 × 1–4.5 cm

8.7−14.8 × 3.0−6.2 cm

Leaf apex

long acuminate

caudate - acuminate

long acuminate

Leaf margin

entire

denticulate

entire

Leaf abaxial surface

densely covered with cream or tawny-colored woolly indumentum

abaxial soft silky texture due to the presence of dense tawny indumentum

abaxial surface covered with dense tawny-colored woolly indumentum

Leaf adaxial surface

glabrous

coriaceous, glabrous or sparsely pilose above

glabrous

Nerves (pairs)

6–11

7–13

9−11

Inflorescence type

interrupted

uninterrupted

interrupted

Inflorescence  dimension

4–15 × 0.2–0.4 mm

5.5–6.2 × 0.5–0.8 mm

26–70 × 3.5–5 mm

Peduncle length

1–1.5 cm long

2.3–6.5 cm long

1–1.5 cm long

Bracts

glandular golden brown woolly indumentum outside

glandular golden brown woolly indumentum outside

adaxial surface and margins with dense tawny woolly indumentum

Bracteole

tawny woolly indumentum abaxially

golden brown woolly tomentose abaxially

tawny woolly indumentum abaxially

Calyx length

7.7–10.2 mm long

4–6 ×1−1.5 mm long

5.6−6.5 mm long

Calyx

glabrous or rarely hairy with tawny tomentose

dense tawny tomentose abaxially and adaxial glabrous

adaxial surface covered with simple white delicate hairs, abaxial surface densely covered with tawny indumentum

Corolla

light pink; 1.5–1.8 cm long,  hairy

light pink with dark purple venation,

1.5–1.9 cm long, hairy

blue, outer surface with soft tawny tomentose indumentum

Corolla tube

1.1–1.3 cm long

1.0–1.2 cm long,

1.4–1.6 cm long

Corolla lobes

unequal, bi-lipped

unequal, bi-lipped

equal

Stamens

exserted

exserted

inserted

Filament

8.5 –11 mm long

ca. 2.2 cm

10-10.2 mm long

Style

glabrous

glabrous

pubescent

 

 

For figure & images - - click here

 

 

References

 

Augustine, J. (2018). Strobilanthes  Blume in the Western Ghats - The Magnificent Role of Nature in Speciation. Malabar Natural History Society (MNHS), Kozhikode, 152pp.

Augustine, J., E.J. Josekutty & P. Biju (2017).  Strobilanthes sainthomiana - A new species of Strobilanthes Blume (Acanthaceae) from Western Ghats, India. Taiwania 62(1): 63–66.

Biju, P., E.J. Josekutty, D. Rekha & J.R. Wood (2017). Strobilanthes jomyii (Acanthaceae), a remarkable new species from south India. Phytotaxa 332(1): 75–80.

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