Frei, David (2023). The genomic consequences of extinction by hybridization during eutrophication-induced speciation reversal. (Thesis). Universität Bern, Bern
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Abstract
Anthropogenic environmental change is causing the loss of biodiversity at an unprecedented rate. When reproductive isolation between species is contingent on the interaction of intrinsic lineage traits with features of the environment, environmental change can weaken reproductive isolation and result in extinction through hybridization, a process called speciation reversal. The extinction of species results in vacant niche space, and its re-population by adaptation of related or evolutionary new species can enhance the ecological resilience of ecosystems. In Lake Constance, a deep-water whitefish species went extinct through speciation reversal during the period of anthropogenic eutrophication mid last century. Using historical and contemporary samples, we sequenced genomes of all species of the Lake Constance whitefish radiation from before, during and after the eutrophication period. The data indicated that genomic diversity of all three extant Lake Constance whitefish species became strongly reduced during the period of anthropogenic disturbance and has not recovered yet. We show that despite the extinction of the deep-water species, fractions of its genome including regions shaped by positive selection and thus potentially adaptive in deep water, persist within surviving species as consequence of introgression. By sampling a depth transect ranging from shallow to deep water, our data suggests that introgressed variation from the extinct species may potentially facilitate rapid adaptation to the vacant deep-water niche in one of the surviving species. Thus, introgression of old variants derived from extinct species may improve the ecological resilience of communities. Given the prevalence of environmental change, studying the genomic consequences of anthropogenic eutrophication and speciation reversal provides fundamental insights into the evolution of biodiversity, especially its dynamics under environmental change, and informs biodiversity conservation.
| Item Type: | Thesis |
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| Dissertation Type: | Cumulative |
| Date of Defense: | 28 March 2023 |
| Subjects: | 500 Science > 570 Life sciences; biology |
| Institute / Center: | 08 Faculty of Science > Department of Biology > Institute of Ecology and Evolution (IEE) > Aquatic Ecology |
| Depositing User: | Sarah Stalder |
| Date Deposited: | 01 Jul 2025 11:42 |
| Last Modified: | 01 Jul 2025 22:25 |
| URI: | https://boristheses.unibe.ch/id/eprint/6350 |
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