Two New Species of Meiogyne (Annonaceae) from Vietnam, Based on Molecular Phylogeny and Morphology

Meiogyne rubra Jaikhamseub, Damth. & Chaowasku sp. nova and M. vietnamica Jaikhamseub, T.A. Le & Chaowasku sp. nova (Annonaceae) from Vietnam are described and illustrated. Molecular phylogenetic reconstructions based on up to eight plastid DNA regions (matK, ndhF, rbcL and ycf1 exons; trnL intron; ndhF-rpl32, rpl32-trnL and trnL-trnF intergenic spacers) and incorporating 33 accessions (31 species) of Meiogyne were performed. The two new species, as well as M. anomalocarpa, M. caudata, M. chiangraiensis and M. subsessilis are included in molecular phylogenetic analyses for the first time. Two major clades were retrieved within Meiogyne: a small clade consisting of M. anomalocarpa, M. hainanensis and M. kanthanensis, and a much larger clade comprising the remaining accessions. The phylogenetic position of the two new species in the latter clade is obscure. Meiogyne rubra appears to be morphologically most similar to M. monosperma. The former differs from the latter by having a narrower leaf blade, free (vs. basally connate) and longer sepals, longer outer petals and larger inner petals. Meigyne vietnamica is morphologically most similar to M. caudata, but differs from it by having an acute to acuminate (vs. usually distinctly caudate-acuminate) leaf apex, non-prominent (vs. prominent) secondary veins on lower leaf surface and higher number of secondary veins in the leaves. A key to the species of Meiogyne in Vietnam is also provided.