CIBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos, Campus Agrário de Vairão, 4485-661 Vairão, Portugal.
Mol Phylogenet Evol. 2011 Feb;58(2):365-73. doi: 10.1016/j.ympev.2010.12.004. Epub 2010 Dec 16.
A previous study on Hemidactylus turcicus based on mtDNA makers indicated that this gecko has a Middle-East origin, and that the current phylogeographic pattern is the result of a very rapid spread from the east to the west of the species' range. The same study identified two distinct mitochondrial lineages with low differentiation and genetic diversity. Since H. turcicus is known to be closely associated to humanized environments, its present distribution range and phylogeography is frequently interpreted to be the result of recurrent human-mediated introductions. These conclusions used to be the same as those used to interpret the results obtained for the European populations of another gecko, Tarentola mauritanica. However, a recent study has revealed that the phylogeographic pattern of T. mauritanica is not solely the result of a recent colonization, but also of a mitochondrial selective sweep. Could the same be occurring in H. turcicus? To answer this question, two mitochondrial (12S rRNA and cytochrome b) and two nuclear genes (ACM4 and Rag2) were used in this study. From the mtDNA data we confirmed the existence of two distinct phylogeographic lineages; one occurring exclusively in the northern Mediterranean (Clade A), and another one more widespread that is the only lineage present in North Africa (Clade B). In light of these results, we could hypothesize that H. turcicus had its origin in Turkey, and from there Clade A moved to Europe and Clade B to North Africa spreading latter into Europe. However, Clade A presents significantly higher nucleotide diversity for the nuclear DNA compared to the mtDNA, and neutrality tests gave significant results for the mitochondrial data. These results suggest that the lack of mtDNA genetic diversity and structure in the European population of H. turcicus could also be due to a selective sweep, and not only because of a recent colonization. Together with the situation reported in T. mauritanica, the identification of a hitch-hiking process occurring in H. turcicus, represents two unprecedented cases of a selective sweep taking place in the same geographic area shaping the phylogeographic patterns of two unrelated genera of geckos.
先前基于 mtDNA 标记对土耳其壁蜥的研究表明，这种壁虎起源于中东，目前的系统地理格局是该物种分布范围从东向西快速扩散的结果。同一研究确定了两个具有低分化和遗传多样性的线粒体谱系。由于已知土耳其壁蜥与人类化环境密切相关，因此其目前的分布范围和系统地理学通常被解释为人类介导的反复引入的结果。这些结论与之前用于解释另一种壁虎，马氏变色蜥的欧洲种群的结果相同。然而，最近的一项研究表明，马氏变色蜥的系统地理格局不仅是最近殖民化的结果，也是线粒体选择清除的结果。土耳其壁蜥是否也发生了同样的情况？为了回答这个问题，本研究使用了两个线粒体（12S rRNA 和细胞色素 b）和两个核基因（ACM4 和 Rag2）。从 mtDNA 数据中，我们证实了存在两个截然不同的系统地理谱系；一个仅存在于北地中海（A 支系），另一个更为广泛，是北非唯一存在的谱系（B 支系）。鉴于这些结果，我们可以假设土耳其壁蜥起源于土耳其，A 支系从那里迁移到欧洲，B 支系迁移到北非，后来又传播到欧洲。然而，A 支系的核 DNA 核苷酸多样性明显高于 mtDNA，中性检验对线粒体数据给出了显著结果。这些结果表明，欧洲土耳其壁蜥种群 mtDNA 遗传多样性和结构的缺乏也可能是由于选择清除，而不仅仅是由于最近的殖民化。与马氏变色蜥报告的情况一样，在土耳其壁蜥中发生的 hitch-hiking 过程的鉴定代表了两个选择清除事件发生在同一地理区域，塑造了两个不相关的壁虎属的系统地理格局。
