Ilex decapetala (Aquifoliaceae), a new holly species from Vietnam revealed by molecular and morphological approaches.

A new species, Ilex decapetala, is described and illustrated from central Vietnam. It is distinguished by its female flowers with (8-)9-10(-11) pink petals (mostly 10); such a high floral merism is rare within the genus and, on top of this rarity, no other known species of Ilex combines such a high merism with pink corolla. Phylogenetic analyses, based on three nuclear markers (ITS, ETS and nepGS), place the new species in Ilex sect. Prinifoliae with strong support, where it is sister to a clade comprising I. angulata, I. hainanensis, I. pubescens and I. stewardii. Morphologically, I. decapetala resembles I. stewardii most, but differs in having more numerous flowers in female inflorescences (3-18 vs. 1-5) and a higher merism of corolla and androecium of female flowers (8-11 vs. 6-7). In addition, the new species shows similarity to I. umbellulata, which also occurs in central Vietnam, but the latter is distinguished by white flowers with 4-5 petals and staminodes.