Breusing Corinna, Vrijenhoek Robert C, Reusch Thorsten B H
GEOMAR Helmholtz Centre for Ocean Research Kiel, Evolutionary Ecology of Marine Fishes, Düsternbrooker Weg 20, 24105, Kiel, Germany.
Monterey Bay Aquarium Research Institute, 7700 Sandholdt Road, Moss Landing, CA, 95039, USA.
BMC Evol Biol. 2017 Jan 13;17(1):13. doi: 10.1186/s12862-016-0862-2.
The analysis of hybrid zones is crucial for gaining a mechanistic understanding of the process of speciation and the maintenance of species boundaries. Hybrid zones have been studied intensively in terrestrial and shallow-water ecosystems, but very little is known about their occurrence in deep-sea environments. Here we used diagnostic, single nucleotide polymorphisms in combination with one mitochondrial gene to re-examine prior hypotheses about a contact zone involving deep-sea hydrothermal vent mussels, Bathymodiolus azoricus and B. puteoserpentis, living along the Mid-Atlantic Ridge.
Admixture was found to be asymmetric with respect to the parental species, while introgression was more widespread geographically than previously recognized. Admixed individuals with a majority of alleles from one of the parental species were most frequent in habitats corresponding to that species. Mussels found at a geographically intermediate vent field constituted a genetically mixed population that showed no evidence for hybrid incompatibilities, a finding that does not support a previously inferred tension zone model.
Our analyses indicate that B. azoricus and B. puteoserpentis hybridize introgressively across a large geographic area without evidence for general hybrid incompatibilities. While these findings shed new light onto the genetic structure of this hybrid zone, many aspects about its nature still remain obscure. Our study sets a baseline for further research that should primarily focus on the acquisition of additional mussel samples and environmental data, a detailed exploration of vent areas and hidden populations as well as genomic analyses in both mussel hosts and their bacterial symbionts.
杂交区域的分析对于深入理解物种形成过程和物种边界的维持机制至关重要。杂交区域在陆地和浅水生态系统中已得到深入研究，但对于它们在深海环境中的出现情况却知之甚少。在此，我们利用诊断性单核苷酸多态性并结合一个线粒体基因，重新审视了此前关于一个涉及生活在大西洋中脊的深海热液喷口贻贝（Bathymodiolus azoricus和B. puteoserpentis）接触带的假说。
发现混合情况在亲本物种方面是不对称的，而基因渗入在地理上比之前认为的更为广泛。来自亲本物种之一且多数等位基因相同的混合个体在与该物种相对应的栖息地中最为常见。在地理上处于中间位置的喷口区域发现的贻贝构成了一个基因混合群体，未显示出杂交不亲和性的证据，这一发现不支持之前推断的张力带模型。
我们的分析表明，B. azoricus和B. puteoserpentis在一个大的地理区域内进行渐渗杂交，且没有普遍杂交不亲和性的证据。虽然这些发现为这个杂交区域的遗传结构提供了新的见解，但其性质的许多方面仍然不明。我们的研究为进一步研究设定了基线，后续研究应主要集中在获取更多的贻贝样本和环境数据、详细探索喷口区域和隐藏种群，以及对贻贝宿主及其细菌共生体进行基因组分析。
