Based on morphological studies performed on live plants in the field and specimens deposited in herbaria, a new species, Glochidion shanense Gang Yao & Shixiao Luo (Phyllantheae, Phyllanthaceae), is here described and illustrated. The species is morphologically most similar to G. ellipticum Wight, but can be distinguished from the latter by having hairy branchlets, longer pedicels, uniseriate and narrowly triangular sepals of female flowers, 4–5-locular ovaries, stout and cylindric persistent style on fruits.

Phyllanthaceae , Glochidion , Morphology, Myanmar

Glochidion J.R. et G. Forst. is the second largest genus in the tribe Phyllantheae Dumortier, Phyllanthaceae Martynov (Webster 1994). It consists of more than 300 species mainly distributed in the Indo-Pacific, east to southeast Polynesia and south into Australia (Govaerts et al. 2000, Li and Gilbert 2008) and can be distinguished from other members in Phyllantheae by the absence of a floral disc, apiculate anthers, usually confluent styles and fleshy seed-coat (Li 1994, Webster 1994).

Recently, the leafflower plant and leafflower moth system, a new mutualism model system that is similar to the fig-fig wasp and yucca-yucca moth pollination systems, was described between Phyllantheae plants and Epicephala moth (Kato et al. 2003, Kawakita et al 2015, Luo et al. 2017) and it provides a new opportunity to study the mechanisms of biodiversity development and maintenance. Glochidion is the largest host plant lineage within this newly described mutualism system, in which at least five host plant lineages were identified (Kawakita and Kato 2009). However, a comprehensive taxonomic study of Glochidion is still lacking, especially for relevant species distributed in the Indo-China Peninsula, since the latest comprehensive taxonomic investigation of Glochidion from there can be dated back to Beille (1927). Recently, taxonomic studies of Glochidion species from Thailand (van Welzen 2007) and Vietnam (Nguyen 2007) have been conducted. In Myanmar, Kurz (1877) accepted 14 Glochidion species in Forest Flora of British Burma and Kress et al. (2003) recorded 33 Glochidion species in A Checklist of the Trees, Shrubs, Herbs and Climbers of Myanmar.

During the fieldwork in Shan State, eastern Myanmar, in December 2015, two of the authors (J. Cai and X.F. Yang) collected some Phyllantheae specimens and one belongs to Glochidion, which superficially differs from congeneric taxa recorded in Myanmar and its adjacent countries. After a detailed morphological investigation and herbaria examination for all the Glochidion species recorded in this region, it was confirmed that the species is new to science, thus it is formally described below. The new species belongs to section Glochidion, which is characterised by having three stamens in male flowers (Li 1994).

In addition to fieldwork in mountain areas of the eastern Myanmar, the present study also included analyses of Glochidion material from herbaria HITBC, IBSC, K, KUN, P, PE and US, as well as consideration of the taxonomic literature of China (Li 1994, Li and Gilbert 2008), India (Hooker 1887, Balakrishnan and Chakrabarty 2007, Chakrabarty and Balakrishnan 2009), Indo-China Peninsula (Beille 1927), Myanmar (Kurz 1877, Kress et al. 2003), Thailand (van Welzen 2007) and Vietnam (Nguyen 2007). Morphological analyses in the present study were performed on live plants in the field and specimens deposited in herbaria. Herbarium abbreviations follow the Index Herbarium (Thiers 2018+).

The authors are grateful to the Forest Research Institute of Myanmar for permission and support in conducting this study in eastern Myanmar. We are indebted to Mrs. Ling Wang in Kunming Institute of Botany, Chinese Academy of Sciences, for preparing the illustration. This research was financially supported by a project of the Southeast Asia Biodiversity Research Institute, Chinese Academy of Sciences (Grant No. Y4ZK111B01).