Dramatic loss of biodiversity in the last two decades has been associated with human activities. Yet, we understand little of the mechanisms that enable species persistence to anthropogenic environmental changes over evolutionary time. Here, we measured ecological and evolutionary responses of a population of Daphnia magna to multiple anthropogenic stressors over evolutionary time, and assessed the role of historical exposure in adaptive response to recurring environmental stress. D. magna is a keystone grazer in freshwater standing waters and a driver of ecosystem dynamics. As part of its life cycle, Daphnia produces dormant embryos that arrest their development entering dormancy and creating a long-term documentation of evolutionary responses to environmental change. Resurrected dormant stages are maintained as clonal lines in the laboratory, providing us with the unique opportunity of disentangling the role of phenotypic plasticity and genetic adaptation in population responses to environmental stress. We studied phenotypic, physiological, and molecular responses that enabled a population of D. magna to persist across major pollution events. We found that adaptive responses to multiple environmental stressors are not predictable from the responses to single stressors. We also discovered that historical exposure to stress prior to dormancy provides an evolutionary advantage when the stress recurs. However, this advantage is contingent upon the type and severity of environmental stressor. We discovered that response to environmental stress is underpinned by extensive epistasis and pleiotropy, suggesting that standing genetic variation is the clay of evolution in this species.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:753032 |
| Date | January 2018 |
| Creators | Cuenca Cambronero, Maria |
| Publisher | University of Birmingham |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://etheses.bham.ac.uk//id/eprint/8275/ |
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