Jiang Ling-Yan, Qian Zeng-Qiang, Guo Zhi-Gang, Wang Chong, Zhao Gui-Fang
Key Laboratory of Resource Biology and Biotechnology in Western China (Ministry of Education), Northwest University, Xi'an 710069, PR China.
Mol Phylogenet Evol. 2009 Jul;52(1):183-91. doi: 10.1016/j.ympev.2009.03.004. Epub 2009 Mar 16.
The genus Gynostemma (Cucurbitaceae) constitutes a polyploid group of perennial creeping herbs, in whose evolution polyploidization is a key component. With the largest variety of cytotypes (2n=22, 44, 66 and 88) in Gynostemma, G. pentaphyllum is also the most widespread species in this genus. In the present study, we inferred the origins of polyploids in G. pentaphyllum using sequences of the plastid intergenic spacers (trnL-trnF, psbB-psbF and rpl20-rps12) and cloned DNA sequences from two nuclear regions (RPB2 and nrDNA ITS). Phylogenetic analyses of the separate and the combined nuclear gene datasets all supported autoploid origins of polyploids in G. pentaphyllum. Three polyploid populations were more closely related, indicating that significant genetic differentiation may have occurred between diploids and polyploids. We concluded that polyploidization might be an important evolutionary mechanism in the diversification of G. pentaphyllum. On the other hand, no chloroplast DNA (cpDNA) variation was detected in ingroups except the octoploid DL 8x, which possessed a different cpDNA haplotype from the other populations of G. pentaphyllum. This can be explained by limited sample sizes, possible extinction of its diploid progenitors and/or the occurrence of chloroplast transfer through hybridization with other Gynostemma species. However, the distribution of cytotypes in G. pentaphyllum was not as typical as many other autopolyploid complexes. Polyploidization failed to contribute significantly to the expansion of its geographic range. The geographic distribution of diploids and polyploids in G. pentaphyllum may be associated with the past ecological environments of different areas, especially during the glacial period.
绞股蓝属（葫芦科）由多年生匍匐草本植物组成的多倍体类群，在其进化过程中多倍体化是一个关键组成部分。绞股蓝属具有最多样化的细胞型（2n = 22、44、66和88），绞股蓝也是该属中分布最广泛的物种。在本研究中，我们利用叶绿体基因间隔区（trnL-trnF、psbB-psbF和rpl20-rps12）序列以及来自两个核区域（RPB2和nrDNA ITS）的克隆DNA序列推断了绞股蓝多倍体的起源。对单独的和合并的核基因数据集的系统发育分析均支持绞股蓝多倍体的同源多倍体起源。三个多倍体种群关系更为密切，表明二倍体和多倍体之间可能发生了显著的遗传分化。我们得出结论，多倍体化可能是绞股蓝多样化的重要进化机制。另一方面，除了八倍体DL 8x外，在内类群中未检测到叶绿体DNA（cpDNA）变异，八倍体DL 8x具有与绞股蓝其他种群不同的cpDNA单倍型。这可以通过样本量有限、其二倍体祖先可能灭绝和/或通过与其他绞股蓝属物种杂交发生叶绿体转移来解释。然而，绞股蓝细胞型的分布并不像许多其他同源多倍体复合体那样典型。多倍体化对其地理范围的扩展贡献不大。绞股蓝中二倍体和多倍体的地理分布可能与不同地区过去的生态环境有关，特别是在冰川期。
