Department of Fish Ecology and Evolution, Centre of Ecology, Evolution and Biogeochemistry, EAWAG Swiss Federal Institute of Aquatic Science and Technology, Kastanienbaum, Switzerland.
Division of Aquatic Ecology and Evolution, Institute of Ecology and Evolution, University of Bern, Bern, Switzerland.
Mol Ecol. 2023 Feb;32(4):841-853. doi: 10.1111/mec.16791. Epub 2022 Dec 2.
Anthropogenic disturbances of ecosystems are causing a loss of biodiversity at an unprecedented rate. Species extinctions often leave ecological niches underutilized, and their colonization by other species may require new adaptation. In Lake Constance, on the borders of Germany, Austria and Switzerland, an endemic profundal whitefish species went extinct during a period of anthropogenic eutrophication. In the process of extinction, the deep-water species hybridized with three surviving whitefish species of Lake Constance, resulting in introgression of genetic variation that is potentially adaptive in deep-water habitats. Here, we sampled a water depth gradient across a known spawning ground of one of these surviving species, Coregonus macrophthalmus, and caught spawning individuals at greater depths (down to 90 m) than historically recorded. We sequenced a total of 96 whole genomes, 11-17 for each of six different spawning depth populations (4, 12, 20, 40, 60 and 90 m), to document genomic intraspecific differentiation along a water depth gradient. We identified 52 genomic regions that are potentially under divergent selection between the deepest (90 m) and all shallower (4-60 m) spawning habitats. At 12 (23.1%) of these 52 loci, the allele frequency pattern across historical and contemporary populations suggests that introgression from the extinct species potentially facilitates ongoing adaptation to deep water. Our results are consistent with the syngameon hypothesis, proposing that hybridization between members of an adaptive radiation can promote further niche expansion and diversification. Furthermore, our findings demonstrate that introgression from extinct into extant species can be a source of evolvability, enabling rapid adaptation to environmental change, and may contribute to the ecological recovery of ecosystem functions after extinctions.
人为干扰生态系统正以前所未有的速度导致生物多样性丧失。物种灭绝常常导致生态位未被充分利用，而其他物种的殖民化可能需要新的适应。在德国、奥地利和瑞士三国交界的康斯坦茨湖，一种特有深海白鲑物种在人为富营养化期间灭绝。在灭绝过程中，深水物种与康斯坦茨湖的三种现存白鲑物种杂交，导致潜在适应深水生境的遗传变异的基因渗入。在这里，我们在一个已知的这种现存物种——大鳞大麻哈鱼的产卵场的水深梯度上进行了采样，并在比历史记录更深的深度（深达 90 米）捕捉到了产卵个体。我们总共对 96 个全基因组进行了测序，每个样本 11-17 个，共来自六个不同产卵深度的种群（4、12、20、40、60 和 90 米），以记录沿水深梯度的种内基因组分化。我们鉴定了 52 个潜在受到深度（90 米）和所有较浅（4-60 米）产卵栖息地之间分歧选择的基因组区域。在这 52 个基因座中的 12 个（23.1%），历史和当代种群的等位基因频率模式表明，来自灭绝物种的基因渗入可能促进了对深水的持续适应。我们的结果与协同进化假说一致，该假说提出，一个适应性辐射成员之间的杂交可以促进进一步的生态位扩展和多样化。此外，我们的研究结果表明，来自灭绝物种的基因渗入可以成为进化能力的来源，使物种能够快速适应环境变化，并可能有助于生态系统功能在灭绝后恢复。
