Begonia medogensis, a new species of Begoniaceae from Western China and Northern Myanmar

Abstract Begonia medogensis JianW.Li, Y.H.Tan & X.H.Jin, a new species of Begoniaceae, is described and illustrated by colour photographs. Begonia medogensis is distributed in western China and northern Myanmar. It has erect stems, is tuberless, has many triangular to lanceolate leaves, base slightly asymmetric, margins remotely and irregularly denticulate; staminate flowers have 4 perianth segments, with outer 2 segments broadly ovate, inner 2 spathulate; pistillate flowers have 5 perianth segments, unequal, outer 4 broadly ovate, inner 1 spathulate. The new species is assigned to section Platycentrum and can easily be distinguished from the other species in the section.


Introduction
Begonia L. (1753) is amongst the largest genera in the angiosperms, with more than 1800 species widely distributed in the tropical and subtropical areas of the world (Ku et al. 2007;Chen et al. 2018) and numerous hybrids and cultivars popular in the horticultural market (Gregório et al. 2015). South America and Asia have the richest diversity of Begonia, with many new species still being described (such as Chen et al. 2018a, Camfield and.
During our botanical survey to Medog County, Tibet, western China in late 2017, Begonia specimens, including DNA samples, were collected. The DNA samples were kept in a freezer and specimens were deposited in HITBC and PE for further study. The same species has been discovered in our botanical survey of Kachin State, northern Myanmar, in 2017. Results from our study indicate that it is a species new to science, which we describe here.
Phenology. Flowering from October to December. Distribution and habitat. This new species grows in subtropical areas in Beibeng town, Medog County, Tibet, China, at an elevation of 700-1400 m and in Putao district, Kachin state, Myanmar, at an elevation of 600-1200 m.
Etymology. The species is named after the holotype locality, Medog County, in Tibet, China.
Note. Morphologically, the new species is similar to B. goniotis, B. griffithiana, B. nepalensis and B. sandalifolia, but differs from them by the shape of stipules and leaves, base and margins of leaves, both male and female flowers having unequal perianth segments, cylindroid ovary etc. (see Table 1).