A new species of Argyreia (Convolvulaceae) from Myanmar

Abstract: Argyreia decemloba Traiperm, Fujikawa & Staples, a new species of Convolvulaceae from Natma Taung National Park, Chin State, Myanmar, is described here with detailed illustrations and summaries for its distribution, ecology and IUCN conservation status. This new species is a high-climbing twiner that can be distinguished by a white or pale yellow corolla with a deep red or purple-black colour inside at the base of the tube, a ten-lobed corolla limb, and staminal filament bases expanded and densely covered by hispid hairs. Argyreia decemloba is here assessed as Near Threatened (NT) following IUCN Red List categories. Citation: Traiperm P., Fujikawa K., Chitchak N., Srisanga P., Maknoi C. & Staples G. 2019: A new species of Argyreia (Convolvulaceae) from Myanmar. – Willdenowia 49: 65–70. doi: https://doi.org/10.3372/wi.49.49108 Version of record first published online on 8 April 2019 ahead of inclusion in April 2019 issue.


Introduction
Located at the western edge of Southeast Asia and the eastern edge of the Indian subcontinent, Myanmar is a unique country where the Indian, Sino-Japanese, Southeast Asian and Malesian floristic regions intersect. Myanmar is well known for its rich plant diversity (Kress & al. 2003), resulting from the combined interaction of its geography, topography, climate, patterns of seasonal rainfall, and its high mountains and major rivers. Whereas comparatively little inventory-based botanical field work has been undertaken there, field investigations and the publication of Floras in surrounding countries have been actively progressing.
Based on a memorandum of understanding signed by the Kochi Prefectural Makino Botanical Garden, Japan, and the Forest Department of Myanmar, the Makino Botanical Garden and its associated international partner institutions have been conducting plant inventory research since 2000 (Tanaka 2005;Fujikawa 2016 One focus of this research has been documenting the flora of Natma Taung National Park, formerly known as Mount Victoria. Between 2002 and 2014 a total of 15,836 collections were made in the park and contiguous areas. The first set of duplicates collected in the Natma Taung National Park is deposited in the Natma Taung National Park Office. Additional duplicates are distributed to herbaria as cited below. Herbarium codes follow Index herbariorum (Thiers 2018+). The ongoing project aims to publish the first taxonomic enumeration of the plants occurring within Natma Taung National Park, Chin State. An international collaborative team of botanists have, so far, identified 2364 species representing 183 families that occur there.
Many interesting species of Convolvulaceae have been found by the field teams during the collecting programme in the Natma Taung National Park. In the course of preparing the Convolvulaceae account for the Taxonomic Enumeration of Flowering Plants of Natma Taung, Chin State, Myanmar (Staples submitted), several collections of an Argyreia Lour. could not be matched with any known species. These specimens characterize a liana with broadly elliptic leaves, pendulous, capitate inflorescences on short peduncles with many overlapping bracts, and bicoloured flowers with a distinctive 10-lobed corolla limb. Concurrently with preparation of the family account for the Enumeration, a comprehensive nomenclatural review of the entire genus Argyreia was completed and published (Staples & Traiperm 2017) and our review confirmed that this Argyreia from Natma Taung did not, in fact, have a scientific name. Thirty-six species of Argyreia are distributed in Myanmar (Staples & Traiperm 2017) and this new one brings the total to 37. We describe the new species here.

Material and methods
Plant materials were collected from the field in Natma Taung National Park, Myanmar, between 2004 -2013. Measurements reported here were taken from dried herbarium specimens. Type specimens of morphologically similar species were compared and verified directly or from digital images available online. Relevant literature, primarily protologues for similar species, was consulted. A preliminary conservation assessment was prepared based on the IUCN Red List categories and criteria (IUCN 2012), using GeoCAT (Bachman & al. 2011) to calculate the Extent of Occurrence (EOO) metrics. Diagnosis -Three species of Argyreia are known to have a white or pale yellow corolla with a deep red or purple-black colour inside at the base of the tube as well as a 10-lobed limb: A. barbata (Wall.) Raizada; A. maymyensis (Lace) Raizada; and A. decemloba (Table 1). Argyreia barbata and A. maymyensis have quite narrow, linear inflorescence-and floral bracts that do not cover up the calyx and corolla base; the hispid-hirsute indumentum of A. barbata, composed of dense, bristly hairs may obscure the floral organs underneath. In contrast, A. decemloba has broad, laminar inflorescence-and floral bracts that cover the floral organs underneath; the abaxial surface of the bracts has a completely different, dimorphic indumentum composed of two different trichome types (Table 1).
Distribution and ecology -So far known only from Chin State, Myanmar, occurring at elevations of (740 -)1025 -1200(-1530) m. A high-climbing twiner in trees and shrubs inhabiting open, sunny places such as roadsides, footpaths in secondary forest, edges of deciduous forest, clearings in evergreen forest, and in semievergreen forest; preferring moist soils along streams or the banks of rivers. The soil type has not been reported.
Conservation status -Based on the eight known collection sites, the Extent of Occurrence (EOO) is 641 km 2 when calculated in the GeoCAT system (Bachman & al. 2011). Accordingly, the species would fall into the IUCN category of Vulnerable (IUCN 2012). However, Argyreia decemloba has been collected three times within the last five years and is found in a protected area: the Natma Taung National Park. We therefore assess the species as Near Threatened (NT) at the present time and point out that further fieldwork is needed to assess changes in population distribution and abundance in the future.  Fujikawa & al. 94296,Kuroiwa & al. 30480,Funakoshi & al. 85034; four collections at Mindat Township, Law Shein 88246, Fujikawa & al. 90722, Fujikawa & al. 95008, Ling Shing Maung & Cho Cho Win 24391;one collection at Matupi Township, Aung & al. 92530.