Uncovering five new species of Polyalthia (Annonaceae, Miliuseae) from Thailand: molecular and morphological congruence

Based on molecular phylogenetic analyses using seven plastid DNA markers (matK, rbcL, ndhF and ycf1 exons; trnL intron; psbA-trnH and trnL-trnF intergenic spacers) and detailed morphological investigations, five new species of Polyalthia Blume (Annonaceae Juss.) from Thailand are recognized, described and illustrated. These species are: P. acuminatissima Wiya, Damth. & Chaowasku sp. nov. (from Nakhon Phanom Province, northeastern region), P. esanensis Wiya, Damth. & Chaowasku sp. nov. (from eastern and northeastern regions), P. chiangmaica Wiya, Damth. & Chaowasku sp. nov. (from Chiang Mai Province, northern region), P. maxwelliana Wiya, Chanthamrong & Chaowasku sp. nov. and P. miliusifolia Wiya, Chanthamrong & Chaowasku sp. nov. (both from Kanchanaburi Province, southwestern region). All five species belong to one of the three major clades within the genus. Three of them (P. acuminatissima, P. esanensis and P. chiangmaica) were previously misidentified as P. evecta (Pierre) Finet & Gagnep., which is polyphyletic. Comparisons with their phylogenetically related or morphologically similar species are provided and a key to the species of this major clade occurring in Thailand is included. The conservation status of all five new species is provisionally assessed as Data Deficient.