Strobilanthes Blume (Acanthaceae) in Myanmar, a new species and an updated checklist

A brief history of the discovery of Strobilanthes species in Myanmar is presented. The revival of fieldwork in recent years has resulted in many new records, so an updated checklist of all known species from the country is needed. Selected specimens are cited and distribution notes provided. One new species, Strobilanthes hians J.R.I.Wood & K.Armstr., with unusual pollen, is described and illustrated bringing the total of recognised species in the country to 81 with six additional infraspecific taxa.


Introduction
Myanmar is a country of great topographical diversity with snow-capped Himalayan mountains in the north, the plains of the Ayeyarwady (Irrawaddy) River and its tributaries in its central heartlands and a series of forest covered hills on both its western and eastern borders. This diverse topography is reflected in a great variety of forest types ) with a very diverse flora. One of the most species-rich and characteristic genera of forest plants occurring throughout Myanmar is the genus Strobilanthes Blume.
The earliest records of Strobilanthes from Myanmar date from 1832 when Nees published the Acanthaceae for Wallich's Plantae Asiaticae Rariores (Nees 1832), which included species of Strobilanthes collected by Nathaniel Wallich himself from Taong Dong, which he visited during his participation in an official mission to the court at Ava. Additional records emerged steadily during the 19 th century, initially from British occupied Tenasserim (Tanintharyi) where collections were made by J. W. Helfer, R. H. Beddome and others. From the 1850s onwards, important collections were made from the interior of Myanmar, notably by Dietrich Brandis, Sulpiz Kurz (1877), and Henry Collett (Collett & Hemsley 1890). General Henry Collett was not the only active British soldier botanist, another being Sidney Miles Toppin who made the first significant collections from Kachin State. Interesting observations (Anon. 1895) and records were added by forestry officers of whom John Henry Lace was the most important. Travellers and professional plant collectors, including Alfred Meebold, George Forrest, Reginald Farrer and Frank Kingdon Ward, found unusual species of Strobilanthes in remote parts of northern Myanmar in the early twentieth century. Much the most significant of these collectors was Kingdon Ward, who found numerous new species over a long career as can be appreciated by the frequency of his name in the citations in the following lists. He was accompanied by Chit Ko Ko on his last expeditions to Kachin and Chin States in the 1950s.
There were few new discoveries in the second half of the twentieth century but since 2000, there has been renewed impetus as a result of collaboration between the Forest Department of the Ministry of Natural Resources and Environmental Conservation in Myanmar and scientific institutions in other countries. Japanese botanists from the Makino Botanical Garden working with colleagues from Myanmar have made inventories and carried out extensive studies focussed on Natma Taung National Park in Chin State (Fujikawa 2021), but have also been involved in fieldwork in Kachin, Kayin and Shan States. More recently another group of Japanese botanists led by Nobuyuki Tanaka from the National Museum of Nature and Science, Tsukuba, have also been carrying out field work. Since 2014, the New York Botanical Garden has been involved in an initiative to document the flora of Myanmar's Northern Forest Complex through botanical inventories in and around Hkakaborazi National Park and Hponganrazi Wildlife Sanctuary in Kachin State, and Htamanthi Wildlife Sanctuary and the surrounding Naga Hills in Sagaing Region. The new species described in this paper was collected in the vicinity of Layshi, in the Naga Self-Administered Zone during an expedition in 2017.
Today 81 species of Strobilanthes are recorded from Myanmar, representing probably the third largest number of Strobilanthes species occurring in a single country, only India and China having more. Twenty-five of these species were not included, even under a synonym, in the most recent checklist of Myanmar plants . Some of the species present in Myanmar are quite widespread extending from northern India across much of SE Asia and include S. auriculata, S. atropurpurea, S. echinata and S. tomentosa (authorities in this section are provided in the checklist below). However, many have a more restricted distribution. Of the 81 species nearly one quarter (20) appear to be endemic to Myanmar. As might be expected, significant numbers are shared with neighbouring countries, about 13 with Thailand, nine with India and six with China. Of some interest are a group of species which are absent from Thailand but found in the island of Sumatra including S. brunelloides, S. inflata and S. pedunculosa but several other species, such as S. cruciata and S. serpens, show a somewhat similar distribution although these are also recorded from Thailand. Within Myanmar species are found in all parts of the country and there is no outstanding centre of endemism but Kachin State is richer in endemics than others with some six species restricted to it.
Strobilanthes species are most common in hill country enjoying a seasonal monsoon climate and are generally absent from the plains. The precise habitat and altitude range of most species is not accurately known but only a few species are found commonly above about 2500 m (S. atropurpurea, S. lachenensis, S. tanakae) and only one, S. oresbia, is certainly recorded above 3000 m. Rarely altitude can provide a useful clue to identification. S. hamiltoniana, for example, is usually found below 1200 m, whereas the somewhat similar S. euantha usually grows above 1500 m. The only species documented in Myanmar as being plietesial is S. rufescens (Anon. 1895), but several species, such as S. echinata, are known to be pliestesial in other parts of their range. However, many of the rare species are likely to be plietesial and will only be found in flower at irregular intervals.
Strobilanthes does not lend itself to a Linnean subclassification (Carine & Scotland 2002) but certain groups are apparent based on morphology and the very limited molecular data available. Perhaps the most important in Myanmar is the group placed by Bremekamp (1944) in Gutzlaffia Hance, because of its distinctive echinulate pollen. This consists of about seven species of which five are present in Myanmar, S. aprica, S. connata, S. gregalis, S. obtusibracteata and S. rosea, the last four being endemic to the country. More numerous are species which conform to Goldfussia Nees in having ellipsoid, ribbed pollen combined with the anthers of the shorter stamens subglobose and incurved. Species in this group, which is diverse throughout the Himalayan region and South China as well as Myanmar, include Strobilanthes arenicola, S. capitata, S. dimorphotricha, S. paniculiformis, S. shanensis and S. tanakae.

Materials and Methods
In the first place, this paper is based on a survey of the relevant literature recording the presence of Strobilanthes in Myanmar since the beginning of the 19th century. The second main source of information has been the collections held in the herbaria at BM, CAL, E, K, MBK, NY and TI (acronyms follow Thiers 2021, continuously updated). In recent years fieldwork, principally by Jin Murata, Nobuyuki Tanaka, Kazumi Fujikawa and Kate Armstrong and colleagues, has increased the number of Strobilanthes records considerably. An earlier paper (Wood & Scotland 2009) described two new species, S. muratae and S. tanakae, based on recent fieldwork and a further species is described here. The description is based on the specimen and photographs taken by one of us (KA) and details were observed using a binocular microscope. Pollen was extracted from a single unopened bud by TW and acetolysed following Erdtman (1960). Acetolysed pollen was then mounted on 15 mm stubs and coated with a single layer of gold/palladium in a Polaron SC7640 sputter coater, before being imaged with a JEOL JSM-7010F Plus field emission SEM operating at either 5 or 15kV.

RECOGNITION.
The gaping subcampanulate corolla with four exserted stamens immediately stands out as it is a relatively unusual character found in very few other species of Strobilanthes. This species appears to be closest to S. rostrata Y.F.Deng & J.R.I.Wood from Yunnan in China in its slightly unequal, glabrous or near glabrous leaves, terminal inflorescence with branched leafless spikes and ±linear bracts and bracteoles but differs in the glabrous calyx, bracts and bracteoles (not thinly glandular-pilose), and the white tomentellous corolla (not blue, not glabrous). It might also be compared with S. helicta T.Anderson but the inflorescence of S. helicta is clearly axillary and the corolla is glabrous and strongly ventricose. The pollen is of an unusual type superficially similar to that of S. japonica (Thunb.) Miq., S. oligantha Miq. and its allies (Deng et al. 2006: 372) but clearly ellipsoid in shape and with tectum apparently absent. DISTRIBUTION & HABITAT. Strobilanthes hians is only known from the type collection made in a patch of remnant forest at 1,275 m near Layshi, a large town in the Naga Hills (Map 1). The area is classified as belonging to the "Sagaing warm temperate rainforest" ecosystem (Murray et al. 2020a, b), a type of closedcanopy, humid, mostly evergreen forest occurring at intermediate elevations along the north-western bor-   CONSERVATION STATUS. This species is only known from a single collection. All evidence suggests it is very restricted in its distribution. The only known locality is a small patch of forest near Layshi, a town in the Naga Hills. The surrounding areas are disturbed by periodic slash and burn for agriculture. The site is highly vulnerable to encroachment in the near future. Therefore, we consider a placement in the Vulnerable category under VU D2 (IUCN 2017) to be appropriate. PHENOLOGY. Found in flower in November. ETYMOLOGY. The specific epithet is in reference to the gaping shape of the open corolla.

List of Strobilanthes species recorded from Myanmar
The list is arranged alphabetically under accepted name. Collections are cited by Region/State. While all types have been cited (if from Myanmar), only selected specimens are cited where several collections are known from the same or nearby localities. An asterisk* indicates type number of accepted species. Notes have been added on points of taxonomic or distributional interest with references to significant other publications. Full synonymy is not provided for widespread species such as Strobilanthes echinata, but basionyms and all names used in publications related to the Myanmar flora are provided.
We have cited herbaria where we know or are confident there are duplicates of each collection but collections may not always have been distributed as expected and more may be present in CAL and RAF than we know of.
Strobilanthes flava Kurz (1870: 78). Ruellia flava Roxb. (Roxburgh 1832: 43). Hemigraphis flava (Kurz) C.B.Clarke (1884: 426). Sericocalyx flavus (Kurz) Bremek. (Bremekamp 1944: 163 98°59'E. The Myanmar collection is slightly anomalous because of the larger calyx lobes, 13 -15 × 2 -4 mm, which appear to be free at the base. We have taken the opportunity to illustrate the pollen of this species (Fig. 2B) as this has never been published before. It is similar to the ellipsoid, ribbed pollen common in Strobilanthes but more obviously narrowed at the two poles than in most species.
Strobilanthes microcarpa T. Anderson (1867: 482 Strobilanthes moschifera Blume (1826: 800). Adenostachya moschifera (Blume) Bremek. (Bremekamp 1944: 192). Strobilanthes haplanthoides T. Anderson (1867: 471). Pteracanthus nobilis (C.B.Clarke) Bremek. (Bremekamp 1944: 199). Strobilanthes petelotii Benoist (1934: 731 NOTE. There is an extensive discussion of the characteristics and peculiarities of this species together with a map of its wider distribution in Wood & Scotland (2003a: 85 -89). There is also a very interesting discussion of its mass flowering in an anonymous paper in Indian Forester 21: 47 -48 (Anon. 1895). This species is remarkable for specimens, such as Cubitt 212, which have a distinctive reddish shaggy indumentum on its stems. This is a rare phenomenon in Strobilanthes but also a feature of some specimens of S. tomentosa, but in that species the indumentum is white. The species is quite variable and the following subspecies can usually be recognised by its oblong (vs elliptic to obovate) bracts:  NOTE. There are numerous records from Natma Taung suggesting it is locally common.