New discoveries of Lanonia (Arecaceae) from northern Vietnam and southwestern China.

A new species of Lanonia (Arecaceae, Coryphoideae, Livistoninae) from Lao Cai, Vietnam, Lanonia nhatii sp. nov., is described and illustrated, and a new record of Lanonia yangchunensis in Guangxi, China, is described based on morphological comparisons, molecular phylogenetic analysis, and pollen morphology. L. nhatii is distinct from all other congeners by its extremely short costa and purplish-black mature fruit. Additional morphological characters, especially variable leaf forms, were found in L. yangchunensis. Phylogenetic analyses using maximum likelihood (ML) and Bayesian inference (BI) methods based on multigene concatenation, including CISP4, CISP5, MS, RPB2, matK, ndhF, and trnD-trnT sequences, provide further support for recognition of L. nhatii as a distinct lineage (ML bootstrap = 100%, BI posterior probability [PP] = 1.00) and of L. yangchunensis with different leaf forms as a monophyletic clade (ML bootstrap = 100%, BIPP = 1.00). Pollen morphology of these two species was investigated and described using scanning electron microscopy (SEM).