Amblyanthus chenii (Primulaceae; Myrsinoideae), a new species discovered growing in the understory of primeval forests in Medog County, southeast Xizang, China, is described based on morphological evidence. This is also the first generic record of Amblyanthus in China. The new species is most similar morphologically to A. multiflorus based on its axillary inflorescence and connate filament, but it differs in its 2-4 cm long condensed panicle and up to half adnation of its sepals and petals. Amblyanthus chenii can also be easily distinguished from other congeneric species by various morphological differences. Phylogenetic analysis based on nuclear ribosomal ITS and six plastid markers indicates that Amblyanthus chenii and Amblyanthopsis burmanica form a clade that is nested within the large pantropical genus Ardisia and is sister to the Ardisia subgenus Crispardisia. The close relationships among Amblyanthus, Amblyanthopsis, and Ardisia subg. Crispardisia are strongly supported by their shared synapomorphy of crenulate leaves with marginal glands.

Appendix S1
Data matrix of ITS sequences

Appendix S2
Data matrix of combined atpB, matk, ndhF, psbA-trnH, rbcL and trnL-trnF sequences.

Appendix S3
Data matrix of combined bases sequences and coded-gaps.

Fig. S1
Bayesian majority-rule consensus tree based on ITS datasets. Posterior probabilities are noted above branches, and the bootstrap values in the maximum likelihood analysis are noted under branches. The asterisk indicates that the value is less than 30 or clade collapsed.

Fig. S2
Bayesian majority-rule consensus tree based on combined six plastid datasets. Posterior probabilities are noted above branches, and the bootstrap values in the maximum likelihood analysis are noted under branches. The asterisk indicates that the value is less than 30 or clade collapsed.

Fig. S3
Bayesian majority-rule consensus tree based on combined bases-gaps datasets. Posterior probabilities are noted above branches, and the bootstrap values in the maximum likelihood analysis are noted under branches. The asterisk indicates that the value is less than 30 or clade collapsed.