Data from: Ancient drainage networks mediated a large-scale genetic introgression in the East Asian freshwater snails

Biogeography and genetic variation of freshwater organisms are influenced
not only by current freshwater connections but also by past drainage
networks. The Seto Inland Sea is a shallow enclosed sea in Japan, but
geological evidence showed that a large freshwater drainage had
intermittently appeared in this area between the late Pliocene and
Pleistocene. Here we demonstrated that this paleodrainage greatly affected
the genetic variation of the East Asian freshwater snails, Semisulcospira
spp. We found that the mtDNA haplotypes originated in the Lake Biwa
endemic Semisulcospira species at the upstream side of the paleodrainage
were frequently observed in the riverine Semisulcospira species at its
downstream side. The genome-wide DNA and morphological analyses
consistently showed that there was no clear evidence of nuclear
introgression between the Lake Biwa endemics and riverine species. These
results suggest that the large paleodrainage had facilitated mitochondrial
introgression and had broadly spread the introgressed mtDNA haplotypes to
its downstream region around the Seto Inland Sea. Our study highlights the
role of paleodrainages in shaping the genetic variation of freshwater
organisms.

淡水生物的生物地理学特征与遗传变异，不仅受当前淡水连通格局的影响，亦受制于既往水系网络的演化。濑户内海（Seto Inland Sea）是日本境内的浅海封闭海域，地质证据显示，在上新世（Pliocene）晚期至更新世（Pleistocene）期间，该区域曾间歇性形成大型淡水古水系。本研究证实，该古水系对东亚淡水螺类Semisulcospira属（Semisulcospira spp.）的遗传变异产生了显著影响。我们发现，古水系上游侧的琵琶湖（Lake Biwa）特有Semisulcospira属物种所携带的线粒体DNA（mtDNA）单倍型（haplotype），在其下游侧的河流生境Semisulcospira属物种中高频检出。全基因组DNA与形态学分析均一致表明，未发现琵琶湖特有物种与河流生境物种之间存在明确的核基因渐渗（introgression）证据。上述结果表明，该大型古水系曾促进了线粒体基因渐渗，并将渐渗获得的线粒体DNA单倍型广泛扩散至濑户内海周边的下游区域。本研究凸显了古水系在塑造淡水生物遗传变异格局中的关键作用。