วิวัฒนาการชาติพันธุ์เชิงโมเลกุลของพืชสกุลสังหยู (วงศ์กระดังงา) โดยเน้นชนิดที่พบในประเทศไทย

Abstract

The genus Pseuduvaria belongs to tribe Miliuseae of subfamily Malmeoideae. Members of this genus are treelets and trees distributed in Southeast Asia (including southern China) to New Guinea and northern Australia. According to the generic monograph and subsequent studies, 57 species of Pseuduvaria have been reported, with 10 species occurring in Thailand. However, there are still several unidentifiable collections. Consequently, the objective of this study is to determine the taxonomic status of these unidentifiable collections from Thailand by molecular phylogenetic reconstruction (parsimony, maximum likelihood, and Bayesian methods) using a combination of six plastome regions (atpB-rbcL, psbA-trnH, and trnL-trnF intergenic spacers; matK and rbcL exons; trnL intron). Sequences of 48 species of Pseuduvaria and two species of outgroups were obtained from GenBank. Sequences of 12 Pseuduvaria accessions are produced in this study. On the basis of molecular phylogenetic analyses and detailed morphological examinations, three new species of Pseuduvaria from Thailand are recognized: Pseuduvaria sp. 1 and Pseuduvaria sp. 2 from Surat Thani Province, and Pseuduvaria sp. 3 from Narathiwat Province. Pseuduvaria sp. 1, Pseuduvaria sp. 2, P. setosa, P. rugosa, and P. trimera form a clade. In this clade Pseuduvaria sp. 1 is the sister group of P. setosa; both species are distinguishable from each other by diferences in indumentum on young twigs and leaf margin, petiole length, shape of inner petal glands, number of stamens per flower, and monocarp surface. The interspecific phylogenetic relationships of Pseuduvaria sp. 2 are obscure, but this species is more morphologically similar to Pseuduvaria sp. 1 and P. setosa regarding the number of flowers per inflorescence and petal color. Pseuduvaria sp. 2 is distinguishable from these two species by the dissimilar sepal appearance and shape of inner petal glands. Pseuduvaria sp. 3 belongs to a clade that also includes P. fragrans, P. gardneri, and P. multiovulata. Although the phylogenetic relationships in this clade is unresolved, Pseuduvaria sp. 3 differs from the other three species in several features: inner and outer petal shape, shape of inner petal glands, and number of stamens per flower. The number of Pseuduvaria species in Thailand are accordingly increased to 13.