Morphological and genomic evidence for a new species of (Orchidaceae: Epidendroideae) from SW China.

, a new species of mycoheterotrophic orchid from western Sichuan, China, is described and illustrated based on molecular and morphological evidence. It is morphologically similar to , but can be distinguished by bigger flowers, both sepals and petals with 3 veins, and longer lateral lobes of lip. To distinguish the new species and explore its phylogenetic position within subtribe Calypsoinae, this study employed sequences of the nuclear ribosomal DNA (nrDNA) and whole plastome assembled from the genome skimming approach. The plastome is 148,124 bp in length, including a pair of inverted repeats (IRs) of 26,165 bp, a large single-copy region (LSC) of 82,207 bp, and a small single-copy region (SSC) of 13,587 bp. Further, phylogenetic analyses were performed using nrDNA sequence and 79 coding sequences (CDSs) from 26 complete plastomes of subtribe Calypsoinae. The phylogenetic tree based on nrDNA sequence suggested that is a monophyletic group, and strongly support as sister to the rest species of . The plastid tree showed that 10 species grouped into two clades and is most closely related to the North American . and instead of and in the same clade. The plastid tree and nrDNA tree indicate is a paraphyletic. Although the topological conflicts are displayed between plastome and nrDNA phylogenies of , it is still the most closely related to . Comparative analysis showed that populations are characteristic of the intermediate morphological traits between and . The finding of this new species from China shed new light on the phylogeny of and .