Home loving boreal hare mitochondria survived several invasions in Iberia: the relative roles of recurrent hybridisation and allele surfing

Genetic introgression from a resident species into an invading close relative can result from repeated hybridisation along the invasion front and/or allele surfing on the expansion wave. Cases where the phenomenon is massive and systematic, such as for hares (genus Lepus) in Iberia, would be best explained by recurrent hybridisation but this is difficult to prove since the donor populations are generally extinct. In the Pyrenean foothills, Lepus europaeus presumably replaced Lepus granatensis recently and the present species border is parallel to the direction of invasion, so that populations of L. granatensis in the contact zone represent proxies of existing variation before the invasion. Among three pairs of populations sampled across this border, we find less differentiation of mtDNA across than along it, as predicted under recurrent hybridisation at the invasion front. Using autosomal microsatellite loci and X and Y-linked diagnostic loci, we show that admixture across the border is...

遗传渐渗（genetic introgression）指土著物种向入侵的近缘物种发生的基因交流，该过程可通过入侵前沿的反复杂交，或是扩张波上的等位基因冲浪（allele surfing）得以发生。此类大规模且系统性的渐渗现象——例如伊比利亚半岛兔属（Lepus）野兔的相关案例——最佳解释为反复杂交，但由于供体种群大多已灭绝，该结论难以验证。在比利牛斯山麓地带，欧洲野兔（Lepus europaeus）据推测近期取代了格拉纳达野兔（Lepus granatensis），且当前物种边界与入侵方向平行，因此接触带内的格拉纳达野兔种群可作为入侵前原有遗传变异的替代群体。我们在该物种边界沿线选取了三对种群进行采样，结果发现：跨越边界的线粒体DNA（mitochondrial DNA, mtDNA）分化程度低于沿边界的分化程度，这与入侵前沿反复杂交的理论预测相符。通过常染色体微卫星位点（autosomal microsatellite loci）以及X和Y连锁诊断位点（X and Y-linked diagnostic loci）的分析，我们证实，跨边界的遗传混杂（admixture）……