Adaptation to variable pesticide doses – SilentAdapt

(1a) In this project we will investigate short and long term trade-off among pesticide doses, using experiments on E. coli, in the context of mutation landscape theory. (1b) We will then experimentally investigate how low dose may lead to overdominance in resistant diploids yeast. (1c) Finally, we will use long term field data of resistance genes in Culex mosquitoes to investigate how the selective effects of different resistance alleles vary with pesticide dose in the field. (2a) We will first consider an exceptional evolution of RS duplications in Culex mosquitoes. We will characterize the chromosome structure and phenotypic effects of these duplications and will follow their dynamics in natura, in different ecological settings (in particular following end of insecticides treatments). (2b) We will then study to what extent the scenarios for RS duplication evolution observed in the mosquito, but rarely studied in other groups, happen in the laboratory on microbes and under what conditions.

ongoing

This project proposes to organize an international conference on the evolution of resistance to foster the emergence of interdisciplinary synthesis at a large taxonomic scale, with a particular focus on integrating ecological (environmental gradients of doses) and genetic (duplications and other complex genetic changes) realism in the study of resistance evolution and adaptation more generally.

1. Labbé P, Milesi P, Yebakima A, Pasteur N, Weill M, Lenormand T, (2014) Gene-dosage effects on fitness in recent adaptive duplications : ace-1 in the mosquito Culex pipiens. Evolution. 68: 2092-2101.
2. Martin G, Lenormand T. (2015) The fitness effect of mutations across environments:Fisher’s geometrical model with multiple optima. Evolution 69 : 1433-1447

In the last decade, evolutionary biology is again turned to the adaptation process. This is due to a combination of the revival of the theories of adaptation, the explosion of experimental evolution and the need to better understand and predict contemporary evolution in the context of global change. The massive use of pesticides since the 50's was a major revolution in our societies in agronomical, public health and medical practices. The evolution of resistance in bacteria, fungi, plants and animals is probably a situation where the process of adaptation has the most immediate consequences on a massive scale. It represents also an emblematic situation for studying adaptation that has been intensively investigated. However, resistance evolution is most often envisioned in a very simplified ecological context: treated versus non-treated environments. The originality of this project is to focus on the evolution of resistance in the context of a gradient of pesticide concentration, with a particular attention toward adaptation to intermediate and low pesticide exposure. Two major issues remain stumbling blocks in our current understanding of the evolution of resistance and their management in presence of low doses. (1) The first concerns trade-offs among environments with zero, low or high doses of pesticides. In particular it is not clearly established whether adaptation to low dose involves traits and adaptive solutions different from adapting to high doses of pesticides. This question has never been directly addressed to date, despite being crucial to understand the role that low doses of pesticide can play on the evolution of super-resistant mutants and to evaluate how non-target species can cope with widespread exposure to low-dose pesticide pollution. (1a) In this project we will investigate short and long term trade-off among pesticide doses, using experiments on E. coli, in the context of mutation landscape theory. (1b) We will then experimentally investigate how low dose may lead to overdominance in resistant diploids yeast. (1c) Finally, we will use long term field data of resistance genes in Culex mosquitoes to investigate how the selective effects of different resistance alleles vary with pesticide dose in the field. (2) The second major issue is to determine the role of gene duplications in the adaptation process to varying doses. Changes in genes copy number are of a magnitude that has so far been largely underestimated. In particular, ‘RS’ duplications combining resistant (R) and susceptible alleles (S) may combine the best of both worlds in situation involving variable pesticide exposure. (2a) We will first consider an exceptional evolution of RS duplications in Culex mosquitoes. We will characterize the chromosome structure and phenotypic effects of these duplications and will follow their dynamics in natura, in different ecological settings (in particular following end of insecticides treatments). (2b) We will then study to what extent the scenarios for RS duplication evolution observed in the mosquito, but rarely studied in other groups, happen in the laboratory on microbes and under what conditions. Finally, this project proposes to organize an international conference on the evolution of resistance to foster the emergence of interdisciplinary synthesis at a large taxonomic scale, with a particular focus on integrating ecological (environmental gradients of doses) and genetic (duplications and other complex genetic changes) realism in the study of resistance evolution and adaptation more generally. This project will be implemented by three partners internationally at the forefront on these topics. This group meets exceptionally broad range of skills, (theories of adaptation, field studies, modern techniques of molecular biology and experimental evolution) and is directly operational, having already collaborated intensively and repeatedly on these scientific questions.hese scientific questions.