对翼蓼(蓼科)属级位置的重新探讨(英文)

Reappraisal of the generic status of Pteroxygonum (Polygonaceae) on the basis of morphology, anatomy and nrDNA ITS sequence analysis

通过对翼蓼Pteroxygonum giraldii Damm.&Diels及相关属(蓼属Polygonum、何首乌属Fallopia、虎杖属Reynoutria、荞麦属Fagopyrum和金线草属Antenoron)的形态观察、果实解剖学观察、花被片脉序观察、花粉形态、核型分析,以及ITS序列的分析确定了翼蓼和荞麦F.esculentum Moench较远的亲缘关系。其中我们发现翼蓼果实基部有三个角状物明显不同于其他属果实的形态特征。翼蓼外果皮明显加厚,并有零星散布的波状内腔,而荞麦的外果皮很薄,细胞不等径,中果皮极厚。以上证据证明了翼蓼与荞麦属亲缘关系较远。在观察荞麦属和翼蓼的花被片脉络时发现了两种不同的脉序类型,符合将荞麦属分为两个组的划分。翼蓼花被片脉序为三出状,支持将翼蓼归为Persicarieae族。对翼蓼及荞麦属植物的花粉进行比较后,发现荞麦属植物的花粉网孔有明显的内凹穿孔而翼蓼却没有,结果表明二者亲缘关系较远。通过对nrDNA ITS区域序列分析得出翼蓼及相关属为一个单系类群,含有两个稳定的分支:第一个分支由蓼属(萹蓄组sect.Avicularia)、何首乌属、虎杖属的植物组成,第二个分支由蓼属(刺蓼组sect.Echinocaulon、蓼组sect.Polygonum、分叉蓼组sect.Aconogonon、拳参组sect.Bistorta、翼蓼和荞麦属植物组成。同时第二个分支又分成了两个亚分支,蓼属(刺蓼组、蓼组、分叉蓼组、拳参组)和翼蓼属Pteroxygonum植物属于第一个亚支而荞麦属植物属于第二个亚支。结果支持翼蓼不属于荞麦属的范畴。实验结果显示翼蓼是个单型属,属于Persicarieae族。

Gross morphology, fruit anatomy, tepal venation, pollen morphology, chromosome number and ITS sequence of Pteroxygonum Damm. ＆ Diels as well as other related genera （Polygonum, Fallopia, Reynoutria, Fagopyrum, and Antenoron） have been investigated to evaluate the generic status of Pteroxygonum. Pt. giraldii Damm. ＆ Diels has three sharp horns at the base of fruit, which is distinctive among all the genera investigated. Upon observation of fruits under a light microscope （LM）, the exocarp of Pt. giraldii is usually thickened and delimited by the rectangular cells with some sporadic undulating lumen, while that of Fagopyrum is thin-walled and isodiametric to rectangular in the cell shape. Analysis of tepal venation was performed under a stereomicroscope, and two types of tepal venation were found in Fagopyrum and Pteroxygonum. The type I is trifid, observed in Pt. giraldii, F. esculentum Moench, F. dibotrys （D. Don） Hara and F. tataricum （L.） Gaertn. The type II, found in F. caudatum （Sam.） A. J. Li, F. urophyllum （Bur. ＆ Franch.） H. Gross and F. gracilipes （Hemsl.） Damm. ex Diels, has the main vein extending from tepal base with some secondary veins. Evidence from tepal venation supports the previous classification in which Fagopyrum can be divided into a large-achene group and a small-achene group. Pollen morphology was investigated under a scanning electron microscope （SEM）. The exine ornamentation of Pt. giraldii was finely reticulate with lumina diameter wider than muri width. The exine ornamentation in all the examined Fagopyrum species is, however, prominently sunken punctuate. The phylogenetic analysis of nuclear ribosomal DNA （nrDNA） ITS sequences in Pteroxygonum and related genera indicated that all the species form a well-supported monophyletic group with two clades. One includes Polygonum sect. Avicularia Meisn., genus Fallopia and genus Reynoutria, and the other consists of other sections of Polygonum, genus Fagopyrum and Pteroxygonum. The latter clade can be divided into two subclades. Fagopyrum species compose the first one, while Pteroxygonum giraldii, species of Polygonum （except sect. Avicularia） and Antenoron form the second one. In consideration of the above evidence, we conclude that Pteroxygonum is an independent genus in tribe Persicarieae, and should not be merged into the genus Fagopyrum.