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Two new species of Polyalthiopsis (Annonaceae), P. nigra Y.H. Tan & Bin Yang from Guangxi and Yunnan Provinces and P. xui Y.H. Tan & Bin Yang from Yunnan Province, are described and illustrated. P. nigra is morphologically similar to P. chinensis in having narrowly elliptic-oblong, lemon to yellowish green petals, but differs by having obovoid monocarps, a higher number of leaf secondary veins, leaf blades usually widest above the middle, and a lower ratio of leaf blade length to width. P. xui is morphologically similar to P. floribunda in having axillary inflorescences, 1–3(–4) flowers, elliptic leaves, and elliptic-ovate petals, but differs in the numbers of carpels per flower and ovules per carpel. The molecular phylogenetic analysis using five plastid markers confirm that the two new species belong to the genus Polyalthiopsis and show clear interspecific divergences between P. nigra and P. xui and between them and other species in the genus. Detailed descriptions, colored photographs, and habitat and distribution data for the two new species are provided. In addition, the fruit morphology of P. chinensis is described for the first time, based on living collections. Geographical distributions and a diagnostic key for all Polyalthiopsis species are also presented.

Litsea, a non-monophyletic group of the tribe Laureae (Lauraceae), plays important roles in the tropical and subtropical forests of Asia, Australia, Central and North America, and the islands of the Pacific. However, intergeneric relationships between Litsea and Laurus, Lindera, Parasassafras and Sinosassafras of the tribe Laureae remain unresolved. In this study, we present phylogenetic analyses of seven newly sequenced Litsea plastomes, together with 47 Laureae plastomes obtained from public databases, representing six genera of the Laureae. Our results highlight two highly supported monophyletic groups of Litsea taxa. One is composed of 16 Litsea taxa and two Lindera taxa. The 18 plastomes of these taxa were further compared for their gene structure, codon usage, contraction and expansion of inverted repeats, sequence repeats, divergence hotspots, and gene evolution. The complete plastome size of newly sequenced taxa varied between 152,377 bp (Litsea auriculata) and 154,117 bp (Litsea pierrei). Seven of the 16 Litsea plastomes have a pair of insertions in the IRa (trnL-trnH) and IRb (ycf2) regions. The 18 plastomes of Litsea and Lindera taxa exhibit similar gene features, codon usage, oligonucleotide repeats, and inverted repeat dynamics. The codons with the highest frequency among these taxa favored A/T endings and each of these plastomes had nine divergence hotspots, which are located in the same regions. We also identified six protein coding genes (accD, ndhJ, rbcL, rpoC2, ycf1 and ycf2) under positive selection in Litsea; these genes may play important roles in adaptation of Litsea species to various environments.

Myanmar is botanically rich and floristically diverse: one of the world's biodiversity hotspots. However, Myanmar is still very unevenly explored, and until a plant checklist was published in 2003, relatively little work was done on its flora. This checklist included 11,800 species of spermatophytes in 273 families. Since this checklist was published, the botanical exploration of Myanmar has accelerated and there have been many additional publications. We therefore surveyed the literature of taxonomic contributions to Myanmar’s vascular flora over the last 20 years (2000–2019) and compiled a list of new and newly described taxa. Our list includes 13 genera, 193 species, 7 subspecies, 19 varieties, and 2 forms new to science; and 3 families, 34 genera, 347 species, 4 subspecies, 7 varieties, and 1 form newly recorded in Myanmar. Altogether, they represent 91 families and 320 genera. Most of the new discoveries belong to 15 families, with more than 25% (146 taxa) belonging to Orchidaceae. These new discoveries are unevenly distributed in the country, with about 41% of the newly discovered species described from Kachin State in northeast Myanmar. This reflects the incompleteness of our current knowledge of the flora of Myanmar and the urgent need for a greatly expanded effort. The completion of the flora of Myanmar requires more fieldwork from north to south, taxonomic studies on new and existing collections, and some mechanism that both coordinates the efforts of various international institutions and initiatives and encourages continued international cooperation. In addition, producing modern taxonomic treatments of the flora of Myanmar requires the participation of experts on all vascular plant families and genera. There is also an urgent need to attract young scientists to plant taxonomy, to work on inventories, identification, nomenclature, herbarium work, and comparative studies.

In this study, we describe several new taxa belonging to the flora of Myanmar. One new family, Polyosmaceae (Polyosma wallichii Benn.) is recorded. Over ten new genera are recorded for the first time, including Amentotaxus Pilger (Taxaceae), Hydrobryopsis Engler (Podostemaceae), Cyrtosia Blume and Biermannia King & Pantling (Orchidaceae), Eleutharrhena Forman and Haematocarpus Miers (Menispermaceae), Craigia W.W. Smith & W.E. Evans (Malvaceae), Amblyanthopsis Mez (Primulaceae), Huodendron Rehder and Rehderodendron Hu (Styracaceae), Platea Blume (Metteniusaceae), Achyrospermum Blume (Lamiaceae), Christisonia Gardner (Orobanchaceae). In addition, five new species are described and illustrated: Tupistra natmataungensis Y.H. Tan & H.B. Ding, Biermannia burmanica Y.H. Tan & Bin Yang, Impatiens megacalyx Y.H. Tan & H.B. Ding, Amblyanthopsis burmanica Y.H. Tan & H.B. Ding, Platea kachinensis Y.H. Tan & H.B. Ding. The distribution, ecology, phenology, and conservation status of these new species are also described. Keywords: Polyosmaceae, New record genus, New species, Flora, Myanmar