Extreme mtDNA divergences in a terrestrial slug (Gastropoda, Pulmonata, Arionidae): accelerated evolution, allopatric divergence and secondary contact
Extreme mtDNA divergences in a terrestrial slug (Gastropoda, Pulmonata, Arionidae): accelerated evolution, allopatric divergence and secondary contact
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DOI：
10.1111/j.1420-9101.2005.00932.x
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发表时间：
2005-09-01
影响因子：
2.1
通讯作者：
Backeljau, T
中科院分区：
文献类型：
--
作者：
Pinceel, J;Jordaens, K;Backeljau, T
肺腹足类动物种内mtDNA差异极高的水平已被反复报道，并提出了几种假说来解释它们。我们研究了51个种群（n = 843）的高度多态性的陆地蛞蝓阿里翁subfuscus（Draparnaud，1805）在其原生分布范围在西欧的繁殖和繁殖地理。通过结合单链构象多态性（SSCP）分析和核苷酸测序，我们获得了线粒体16 S rDNA片段和核ITS 1片段的个体序列数据。此外，5个多态性等位酶位点进行了评分。根据16 S rDNA序列分析，发现了5个单系单倍型群，其序列差异为9-21%。尽管线粒体序列差异很大，但核ITS 1片段的单倍型群不是单系的，也没有发现单倍型群特异的等位酶等位基因。尽管有证据表明线粒体DNA时钟加快，单倍型组之间的分歧比更新世更古老，它们目前的异地分布范围可能反映了异地分歧和冰川生存在不同的避难所，从那里建立了不同的后冰川殖民路线。两个mtDNA组（S1和S2，21%的序列差异）的范围重叠从法国中部和比利时延伸到不列颠群岛北部。核数据表明，这种二次接触导致了异地分歧群体之间的杂交。因此，至少在两个群体中，线粒体DNA的深层分化只是部分地伴随着生殖隔离的形成。
Extremely high levels of intraspecific mtDNA differences in pulmonate gastropods have been reported repeatedly and several hypotheses to explain them have been postulated. We studied the phylogeny and phylogeography of 51 populations (n = 843) of the highly polymorphic terrestrial slug Arion subfuscus (Draparnaud, 1805) across its native distribution range in Western Europe. By combining the analysis of single stranded conformation polymorphisms (SSCP) and nucleotide sequencing, we obtained individual sequence data for a fragment of the mitochondrial 16S rDNA and a fragment of the nuclear ITS1. Additionally, five polymorphic allozyme loci were scored. Based on the 16S rDNA phylogeny, five monophyletic haplotype groups with sequence divergences of 9-21% were found. Despite this deep mitochondrial divergence, the haplotype groups were not monophyletic for the nuclear ITS1 fragment and haplotype group-specific allozyme alleles were not found. Although there is evidence for an accelerated mtDNA clock, the divergence among the haplotype groups is older than the Pleistocene and their current allopatric ranges probably reflect allopatric divergence and glacial survival in separate refugia from which different post-glacial colonization routes were established. A range-overlap of two mtDNA groups (S1 and S2, 21% sequence divergence) stretched from Central France and Belgium up to the North of the British Isles. The nuclear data suggest that this secondary contact resulted in hybridization between the allopatrically diverged groups. Therefore, it seems that, at least for two of the groups, the deep mtDNA divergence was only partially accompanied by the formation of reproductive isolation.