Abstracts (first author)

Talk 

Rapid evolution of insecticide resistance genes in mosquito populations: a quantitative approach

Author(s): Milesi P, Labbe P, Weill M, Lenormand T

Summary:

How adaptation appears and is later refined by natural selection has been the object of intense theoretical work. However, the testing of these theories is limited by our ability to estimate the strength of natural selection in nature. Selection by insecticide treatments of the Ester resistance gene in populations of the mosquito Culex pipiens in Montpellier area (southern France) is a contemporary example of rapid evolution of an adaptation to environmental changes in natural populations. We observed in twenty years, the emergence and replacement of three resistance alleles at the Ester locus due to the selection pressure of insecticide uses. With continuous sampling for >40 years on a 50 km transect corresponding to a gradient of insecticides treatment, we were able to follow the dynamics of these different alleles in natural populations. Using a population genetics model taking into account environmental variables, we were able to estimate the intensity of the selection pressure, as well as many parameters (genetic and environmental) affecting the dynamics of these alleles. In addition, we were able to analyze the evolution of allele frequencies under various environmental conditions. For example the prohibition by the European instances of OP’s insecticides in 2007 was a full-scale test of the quality of our predictions. I will present this work, which links ecology and evolution, through the integration of environmental data into a genetic model, to analyze the dynamics of adaptive alleles in natural populations. We quantified the selection and environmental parameters conditioning resistance genes dynamic and showed that the relationship between environmental factors and allele dynamics in natural populations is not straightforward.


Video


Abstracts (coauthor)

Gene duplications: a role in adaptive evolution

Author(s): Labbé, P, Milesi P, Weill M, Lenormand T

Summary:

Evolutionary potential is limited by the number and type of genes present, but how these limits shape the evolution of new functions remains a matter of debate. In this context, gene duplications are thought to be the main source of raw material for new evolutionary features: duplications are essentially envisioned as genomic substrates for long-term adaptation. Their early evolution is thus often neglected, notably how gene-dosage modifications affect fitness and condition their first steps. The evolution of insecticide resistance in the mosquito Culex pipiens is one of the few examples of contemporary duplications. Resistance represents a genetic adaptation to the environmental changes induced by insecticides, and as such, provides evolutionary biologists with a contemporary model for studying parameters that influence ongoing adaptation. The ace-1 gene encodes the acetylcholinesterase (AChE1), the target of organophosphate (OP) insecticides. A mutation in this gene causes high resistance levels in many mosquito species. However, a strong genetic constraint drives resistance evolution, as the degree of resistance and the ability to degrade ACh trade off. Recently, we identified in Cx. pipiens new ace-1 alleles that carry one susceptible and one resistant copy associated on the same chromosome. These different duplicated alleles show different dynamics in the field. We propose that duplications are selected to disentangle the two functions, i.e., by improving synapse signaling and mosquito’s fitness while maintaining resistance. I will present our recent work investigating 1) the duplication origin at the molecular level and 2) the complex gene-dosage/fitness relations and their impact in the field dynamics of these innovations. Our work stresses the role of duplications as immediate adaptive features, but shows that their fate is checked by natural selection early on: only those passing its short-term sieve can become seeds for future evolution.

Contacts

Chairman: Octávio S. Paulo
Tel: 00 351 217500614 direct
Tel: 00 351 217500000 ext22359
Fax: 00 351 217500028
email: mail@eseb2013.com

Address

XIV Congress of the European Society for Evolutionary Biology

Organization Team
Department of Animal Biology (DBA)
Faculty of Sciences of the University of Lisbon
P-1749-016 Lisbon
Portugal

Website

Computational Biology & Population Genomics Group 
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