Zhang Hua, Yan Jie, Zhang Guoqiang, Zhou Kaiya
Jiangsu Key Laboratory for Biodiversity and Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing 210046, China.
BMC Evol Biol. 2008 Jan 24;8:21. doi: 10.1186/1471-2148-8-21.
Pleistocene glaciations had considerable impact on phylogeographic patterns within and among closely related species of many vertebrates. Compared to Europe and North America, research on the phylogeography of vertebrates in East Asia, particularly in China, remains limited. The black-spotted frog (Pelophylax nigromaculata) is a widespread species in East Asia. The wide distribution of this species in China makes it an ideal model for the study of palaeoclimatic effects on vertebrates in East Asia. Our previous studies of P. nigromaculata revealed significant subdivisions between the northeast China populations and populations in other regions of the mainland. In the present study, we aim to see whether the deepest splits among lineages and perhaps subsequent genealogical divisions are temporally consistent with a Pleistocene origin and whether clade geographic distributions, with insight into expansion patterns, are similarly spatially consistent with this model.
Using 1143 nucleotides of the mitochondrial cytochrome b gene from 262 individuals sampled from 28 localities, two main clades (clade A and clade B) differing by c. 7.72% sequence divergence were defined from parsimony analyses. The corresponding timing of lineage divergence, 0.92 Mya, indicates a most likely Pleistocene split. The A clade is further subdivided into two sub-clades, A1 and A2 with 1.22% sequence divergence. Nested clade phylogeographical and population demographic analyses suggested that the current distribution of this frog species was the result of range expansion from two independent refugia during the last interglacial period. We discovered a population within which haplotype lineages A and B of P. nigromaculata coexist in the Dongliao area of China by nucleotide sequences, PCR-RFLP and ISSR (inter simple sequence repeat) patterns. The ISSR result in particular supported divergence between the mitochondrial clades A and B and implied introgressive gene flow between the two divergent lineages.
Nested clade phylogeographical and population demographic analyses indicate that the current distribution of P. nigromaculata is the result of range expansion from two independent refugia during the last interglacial period in late Pleistocene. One refugium was in east China and the lower elevations of south-western plateau. The distribution of the other mitochondrial clade is consistent with the presence of a refugium in the Korean Peninsula. The gene flow as detected by ISSR markers suggests a range expansion of the two refugia and a secondary contact between the two highly divergent lineages in the Dongliao (DL) area of northeast China.
更新世冰川作用对许多脊椎动物近缘物种内部及之间的系统发育地理格局产生了重大影响。与欧洲和北美相比，东亚尤其是中国脊椎动物系统发育地理学的研究仍然有限。黑斑侧褶蛙（Pelophylax nigromaculata）是东亚广泛分布的物种。该物种在中国的广泛分布使其成为研究古气候对东亚脊椎动物影响的理想模型。我们之前对黑斑侧褶蛙的研究揭示了中国东北种群与大陆其他地区种群之间存在显著的分化。在本研究中，我们旨在探究谱系间最深的分化以及随后的谱系分支在时间上是否与更新世起源一致，以及分支地理分布（结合对扩张模式的洞察）在空间上是否同样与该模型一致。
利用从28个地点采集的262个个体的线粒体细胞色素b基因的1143个核苷酸，通过简约分析确定了两个主要分支（A分支和B分支），它们的序列差异约为7.72%。谱系分化的相应时间为0.92百万年前，表明最有可能是更新世的分化。A分支进一步细分为两个亚分支，A1和A2，序列差异为1.22%。嵌套分支系统发育地理学和种群统计学分析表明，该蛙类物种目前的分布是末次间冰期两个独立避难所范围扩张的结果。我们通过核苷酸序列、PCR-RFLP和ISSR（简单序列重复区间）模式在中国东辽地区发现了一个黑斑侧褶蛙单倍型谱系A和B共存的种群。特别是ISSR结果支持了线粒体A和B分支之间的分化，并暗示了两个分化谱系之间的渐渗基因流。
嵌套分支系统发育地理学和种群统计学分析表明，黑斑侧褶蛙目前的分布是更新世晚期末次间冰期两个独立避难所范围扩张的结果。一个避难所在中国东部和西南高原的低海拔地区。另一个线粒体分支的分布与朝鲜半岛存在避难所一致。ISSR标记检测到的基因流表明两个避难所的范围扩张以及中国东北东辽（DL）地区两个高度分化谱系之间的二次接触。
