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PeerJ. 2019 Nov 5;7:e7988. doi: 10.7717/peerj.7988. eCollection 2019.

Endless forms of sexual selection.

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Department of Biological and Environmental Sciences, University of Gothenburg, Göteborg, Sweden.
Department of Ecology and Genetics, Uppsala University, Uppsala, Sweden.
Natural History Museum, University of Oslo, Oslo, Norway.
Department of Entomology and Nematology, University of Florida, Gainesville, FL, United States of America.
Institute of Integrative Biology, University of Liverpool, Liverpool, United Kingdom.
Department of Zoology, Edward Grey Institute, University of Oxford, Oxford, United Kingdom.
Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, CO, United States of America.
School of Natural Sciences, Technology and Environmental Studies, Södertörn University, Huddinge, Sweden.
Department of Organismic and Evolutionary Biology and Museum of Comparative Zoology, Harvard University, Cambridge, MA, United States of America.
Gothenburg Centre for Advanced Studies in Science and Technology, Chalmers University of Technology, Göteborg, Sweden.


In recent years, the field of sexual selection has exploded, with advances in theoretical and empirical research complementing each other in exciting ways. This perspective piece is the product of a "stock-taking" workshop on sexual selection and sexual conflict. Our aim is to identify and deliberate on outstanding questions and to stimulate discussion rather than provide a comprehensive overview of the entire field. These questions are organized into four thematic sections we deem essential to the field. First we focus on the evolution of mate choice and mating systems. Variation in mate quality can generate both competition and choice in the opposite sex, with implications for the evolution of mating systems. Limitations on mate choice may dictate the importance of direct vs. indirect benefits in mating decisions and consequently, mating systems, especially with regard to polyandry. Second, we focus on how sender and receiver mechanisms shape signal design. Mediation of honest signal content likely depends on integration of temporally variable social and physiological costs that are challenging to measure. We view the neuroethology of sensory and cognitive receiver biases as the main key to signal form and the 'aesthetic sense' proposed by Darwin. Since a receiver bias is sufficient to both initiate and drive ornament or armament exaggeration, without a genetically correlated or even coevolving receiver, this may be the appropriate 'null model' of sexual selection. Thirdly, we focus on the genetic architecture of sexually selected traits. Despite advances in modern molecular techniques, the number and identity of genes underlying performance, display and secondary sexual traits remains largely unknown. In-depth investigations into the genetic basis of sexual dimorphism in the context of long-term field studies will reveal constraints and trajectories of sexually selected trait evolution. Finally, we focus on sexual selection and conflict as drivers of speciation. Population divergence and speciation are often influenced by an interplay between sexual and natural selection. The extent to which sexual selection promotes or counteracts population divergence may vary depending on the genetic architecture of traits as well as the covariance between mating competition and local adaptation. Additionally, post-copulatory processes, such as selection against heterospecific sperm, may influence the importance of sexual selection in speciation. We propose that efforts to resolve these four themes can catalyze conceptual progress in the field of sexual selection, and we offer potential avenues of research to advance this progress.


Cryptic female choice; Epigenetics; Mate choice; Polyandry; Sensory bias; Sexual conflict; Sexual selection; Signal honesty; Speciation; Sperm competition

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