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Towards an adaptive and genomic understanding of an exaggerated secondary sexual trait in water striders

Abstract : From the DNA molecule to the more complex phenotypes, variation is a universal process in life and living organisms. The innumerable differences that exist between species are probably one of the most manifest examples. Yet, all this diversity would never have occurred in nature without some pre-existing divergence within species. One of the most striking examples of intraspecies variation appears in sexual organisms, between males and females. Understanding the environmental and genetic factors influencing sexual divergence is a longstanding question in evolutionary biology. To this end, I focus here on a new insect model system, Microvelia longipes, which has the particularity to have evolved an extreme case of sexual dimorphism in the rear legs. Males display exaggerated long rear legs compared to females but also an extreme variability in these leg lengths from one male to another. We identified that M. longipes males use their exaggerated legs as weapons during male-male competition. Males with longer legs have more chance to access females on egg-laying sites and therefore increase their reproductive success. Moreover, fitness assays and comparative studies between Microvelia species revealed that the intensity of male competition was associated with the exaggeration and hypervariability of the rear legs in M. longipes males. In a second approach, we studied the developmental and genomic basis of this sexual dimorphism through a comparative transcriptomic analysis and identified genes and genomic regions associated with male exaggerated legs and ultimately with sexual selection. Overall, the integrative approach used in this work allows to establish Microvelia longipes as a promising new model system to study the influence of sexual selection in adaptive evolution.
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Submitted on : Tuesday, November 12, 2019 - 4:42:23 PM
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William Toubiana. Towards an adaptive and genomic understanding of an exaggerated secondary sexual trait in water striders. Biodiversity. Université de Lyon, 2019. English. ⟨NNT : 2019LYSEN058⟩. ⟨tel-02360159⟩

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