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

For Focus, Scope, Aims, Policies, and Guidelines visit https://threatenedtaxa.org/index.php/JoTT/about/editorialPolicies#custom-0 For Article Submission Guidelines, visit https://threatenedtaxa.org/index.php/JoTT/about/submissions#onlineSubmissions For Policies against Scientific Misconduct, visit https://threatenedtaxa.org/index.php/JoTT/about/editorialPolicies#custom-2 For reprints, contact <ravi@threatenedtaxa.org> Note


PLATINUM OPEN ACCESS
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. 2016Josekutty et al. , 2017Josekutty et al. , 2018Sasidharan 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, 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 2004Sasidharan , 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).
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.  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.

J TT
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.   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.