The genus Phaeanthus (Annonaceae, Miliuseae) in Thailand: P. piyae sp. nov. and resurrection of P. lucidus, with molecular phylogenetic analyses

The genus Phaeanthus (Annonaceae, Miliuseae) in Thailand: P. piyae sp. nov. and resurrection of P. lucidus, with molecular phylogenetic analyses

Phaeanthus piyae, a new species from southern Thailand, is described and illustrated. It is morphologically most similar to P. intermedius, which occurs in Peninsular Malaysia, Singapore, Riau Islands, and Sumatra. The new species can be distinguished from P. intermedius by the longer peduncles and pedicels; triangular (vs. filiform-narrowly triangular) sepals; and stigmas that are larger and±elongated club-shaped (vs.±ellipsoid). The conservation status of P. piyae is provisionally assessed. In addition, molecular phylogenetic analyses using up to seven plastid DNA regions (matK, ndhF, rbcL and ycf1 exons; trnL intron; psbA-trnH and trnL-trnF intergenic spacers) and including, among others, five Phaeanthus accessions are carried out. Phaeanthus piyae is sister to a clade composed of the remaining accessions of Phaeanthus. Furthermore, southern Thailand also harbors a second species of Phaeanthus, which appears to be P. lucidus, a heterotypic synonym of P. splendens. Phaeanthus lucidus is herein reinstated; it differs from the sister species P. splendens by possessing a lower number of stamens and carpels per flower, as well as dissimilar placentation. A key to the two species of Phaeanthus in Thailand is given.