Evolving to Xenobiotic Induced Stress

Informations

Funding country

France

Acronym

Evotoxis

URL

-

Start date

1/1/2017

End date

-

Budget

312,788 EUR

Fundings

Abstract

Chemical pollutants from industrial and agricultural sources are significant ecological stressors of the freshwater environment, with more than half of all European waterbodies negatively impacted. Whilst catastrophic discharge events are an obvious threat to biodiversity, they are relatively rare. Long-term effects may be less evident, but frequently pose a more significant impact. One such impact is their influence on the evolutionary trajectories of species, a subject of growing concern in ecotoxicology and environmental risk management. My research will address this problem in the waterflea (cladoceran microcrustaceans of the genus Daphnia), planktonic animals that are critical to the proper functioning of freshwater ecosystems. Daphnia are important models in ecotoxicological risk assessment, and can easily be cultured over many generations, thereby facilitating studies designed to simulate evolution within a laboratory setting. They are also characterized by an interesting reproductive cycle alternating between clonal and sexual reproduction, providing an ideal model to explore the effects of chemical contaminants against a variety of genetic backgrounds. However, one of their most unique properties is the producing of resting eggs (ephippia) that may lay dormant for centuries, yet be resuscitated when exposed to the proper stimuli. This provides an incredibly rare opportunity to study changes in molecular function in a deep historical context, to a time pre-dating the Industrial Revolution and the first exposure of populations to anthropogenic chemical contaminants. Using contemporary and resurrected populations of Daphnia from natural ponds and marshes in western France, an area of important agricultural production, I will explore the effects that pesticide drift has had on the evolutionary history of this important species. I will sample Daphnia currently inhabiting sites located in protected areas with those from neighbouring waters impacted by the unintentional diffusion of agricultural chemicals, contrasting the effects of pesticide exposure on survival and reproduction in multiple independent lines. I will also use the latest advances in sequencing technology to search for genomic signals of natural selection in wild populations, and attempt to validate these results experimentally by comparing functional/physiological differences between groups in the genes identified as under selection. In these same populations, as well as in resurrected historical lines, I will explore how exposure to agricultural contaminants affects the expression of genes at the transcriptional level, both immediately and over many generations of evolution. These results will also be used to identify lineages that differ in their immediate stress response to a chemical contaminant, which will then be used to address an area of fundamental importance in current discussions of evolution: the role of plasticity. Contrasting lines will be subjected to multiple generations of contaminant-induced selection to determine if/how an inherently increased sensitivity in one of key molecular pathways affected by pesticide exposure (the oxidative stress response) influences the evolutionary response to life in a contaminated environment.