Mate choice for good genes or compatible genes : an integrative approach with a focus on the major histocompatibility complex – CMatecHoice

To quantify the impact of mate choice on genetic diversity, three objectives must be met: 1) highlight a mate choice based on genetic characteristics; 2) determine the relative importance of choice for «good genes« and for «compatible genes«; 3) understand the mechanisms. This project is based on a unique dataset collected over several natural populations of alpine marmots in the Alps and the Pyrenees.

Studying the role of genes is a challenge that requires the reliable genotyping of many individuals. Next generation sequencing techniques (NGS) allow to acquire large scale data but a rigorous treatment of these data is necessary. We have developed a methodology and easy to use software to process this data, and we have used it to obtain the genotype of more than 1,000 individuals for 4 loci of the major histocompatibility complex of the alpine marmot. This methodology can be applied to any genetic system or organism and provides highly reliable genotypes. Our results highlight the potential of NGS which, combined with an adequate post-processing allow to obtain highly reliable large-scale genotypes, opening new perspectives for understanding the evolution of functional genes.

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Ferrandiz-Rovira M., Bigot T., Allaine D., Callait-Cardinal M.P., Cohas A. (2015) Large-scale genotyping of highly polymorphic loci by next-generation sequencing: how to overcome the challenges to reliably genotype individuals? Heredity, 114: 485-93.

Although the conservation of biodiversity is a common concern of the human kind and an integral part of a sustainable development (Rio CBD, 1992), the 2010 “Year of biodiversity” sadly reveals that we lose biodiversity at a speed more than one thousand higher than the background and historical rate, thus mortgaging our future. In this Decade of Biodiversity, biodiversity has now to be in the centre of political attention. Mate choice is a true architect of biodiversity. For example, house mice are able to differentiate between different subspecies. This recognition, accompanied by a preference to mate with individuals of their own sub-species, favour the selection against hybridization and thus the diversity among species. If interspecific diversity is now the subject of all the attention, intraspecific diversity is neglected while it represents the true potential of adaptation and evolution of species. The role of mate choice in intraspecific biodiversity remains unclear. Indeed, until recently, only a choice for "good genes" was considered. Such a choice far from promoting biodiversity, could even erode it. More recently, a choice for "compatible genes" had been suggested and has the potential to increase biodiversity within species. To assess the contribution of mate choice in intraspecific biodiversity by establishing the relative importance of these criteria is essential. It is this issue that we want to address with this project. We propose to consider different aspect of an individual's genetic caracteristics such as inbreeding level, relatedness and heterozygosity measured via pedigree or on microsatellites markers. Moreover,the major histocompatibility complex due to its involvement in the immune response and its impact on individual fitness appears as an ideal target for a choice based on genetic characteristics, in particular on "good" and "compatible” genes and such a choice represents a unique opportunity to quantify the impact of mate choice on genetic diversity. To achieve this goal, we need (1) to highlight a choice of partner based on the genetic characteristics; (2) to determine the relative importance of the choice for "good " and for "compatible” genes; (3) to understand the underlying mechanisms, in particular the role of chemical communication. At the interface between 4 disciplines, molecular genetics, chemical ecology, behavioural ecology and population biology and involving 3 international collaborators and 1 platform with recognized expertise in the domain, this project provides an innovative and integrative approach that, while crucial, is currently lacking. It will draw on an exceptional dataset encompassing (1) a unique long term individual-based dataset collected since 1990, on a population of marmots located in the Grand Sassière Nature Reserve (Rhône-Alpes), (2) a mirror of this dataset collected since 2008 on an introduced population of marmots located in the Pyreenes (Spain), (3) and (4) 2 datasets on eight populations of the Alps and the Pyrenees. This project will provide the first keys to quantify the role of mate choice in maintaining and promoting genetic diversity, which will ultimately allow to assess its impact in the process of evolution and adaptation. Such a knowledge will help to adjust management measures and conservation of natural populations. It is particularly critical for endemic and endangered species (especially 2 marmots species close to extinction: M. vancouverensis and M. marmota latirostris) where the conservation of genetic diversity is a major issue. Moreover, thanks to the model species: the alpine marmot, a friendly and emblematic species, this project represents a unique opportunity to educate the public to biodiversity conservation. The relevance and importance of this project has already been realized by two non institutional partners, Earthwatch (field expenses) and the Caixa bank (PhD), that support financially the project.