การจำแนกพืชสกุลการเวกบางชนิดในประเทศไทย ‪(วงศ์กระดังงา)‬ โดยใช้วิวัฒนาการชาติพันธุ์เชิงโมเลกุลและสัณฐานวิทยา

Abstract

Artabotrys is one of the largest genera of Annonaceae and easily recognizable by the presence of hooked peduncles and inflorescence axes, but their species delimitation is somewhat problematic due to highly overlapping morphological traits. So, it is suspected that some scientific names may contain more than one species. In order to prove the existence of such cryptic species complexes in A. harmandii, A. multiflorus, and A. spinosus, a plastid phylogenetic hypothesis (six regions: matK, ndhF, and rbcL exons; trnL intron; trnL-trnF and psbA-trnH intergenic spacers; 37 accessions of Artabotrys, 15 from GenBank), and a combined plastid (five regions: matK, and ndhF exons; trnL intron; trnL-trnF and psbA-trnH intergenic spacers) and nuclear (eight regions: AP3, AT2G32520, GI, HMGS, LFY, MAG1, and ncpGS exons plus introns; PHYA exon) phylogenetic hypothesis (61 accessions of Artabotrys, 51 from GenBank; 12 accessions are the same as those included in the plastid phylogeny) are reconstructed by three methods: parsimony, maximum likelihood, and Bayesian inference. The plastid phylogenetic relationships are largely unresolved, with A. harmandii and A. spinosus being non-monophyletic (i.e. accessions of each species have been recovered in two clades that are not sister to each other), whereas only one accession of A. multiflorus occurring in Kanchanaburi Province (= Artabotrys cf. multiflorus) is amplifiable. Based on the plastid phylogenetic results, it is still inconclusive whether the two clades of A. harmandii and of A. spinosus represent a single species, while Artabotrys cf. multiflorus is morphologically different from the type specimens of A. multiflorus (Myanmar) in several respects: number of flowers per hook; petal shape, apex, length and width; and number of carpels per flower. Therefore, Artabotrys cf. multiflorus is described as a new species. The combined plastid and nuclear phylogenetic results are much more resolved. Artabotrys harmandii appears paraphyletic and one new species is warranted and described. The new species from Chachoengsao Province has usually elliptic leaf blade, acute to broadly acute leaf apex, narrowly elliptic-oblong petals, and subglobose monocarps, whereas the true A. harmandii (from Laos [type] and Sisaket Province) has obovate leaf blade, cuspidate leaf apex, elliptic petals, which are broader and shorter, and ellipsoid monocarps. On the other hand, accessions of A. spinosus from two different localities (Mun and Chi River system vs. Mekong River system) are recovered as a monophyletic group. Although A. spinosus is monophyletic, each lineage is moderately long corresponding to its mutations. Their morphological features, however, require further in-depth investigation before a solid conclusion on the taxonomy of A. spinosus can be made.