Call for abstracts for the symposium on "The maintenance of adaptive polymorphisms" (Symposium S48) at ESEB 2025, taking place from 17-22 August in Barcelona, Spain. ABSTRACT SUBMISSION DEADLINE 25th April 2025 https://eseb2025.com/call-for-abstracts/ In the face of decades of work, the maintenance of heritable variation for fitness remains an unresolved question in population genetics. Natural populations often display much more fitness variance than mutation-selection balance or single-locus heterozygote advantage alone can account for. To explain this surplus variance, alternative processes, such as negative frequency-dependent selection, multi-locus balancing selection, spatially or temporally varying selection, antagonistic selection, or genotype-by-environment interactions, have been invoked, yet fundamental questions about the role of these mechanisms in maintaining polymorphism remain open. Despite growing theoretical and empirical interest, we still lack a comprehensive understanding of such "non-classical" forms of balancing selection and their relative contributions to the maintenance of genetic variance. This symposium aims to spotlight emerging examples of non-classical balancing selection and to address key outstanding questions: (1) How prevalent are these processes in natural populations, and how frequently do they interact? (2) Do they produce distinct population genetic signatures? Can we disentangle such signatures in genomic data? Alternatively, can we devise experiments to identify the type of balancing selection at play? To foster a discussion of these fundamental issues, our symposium aims to bring together theoreticians and empiricists studying a variety of processes and systems that result in balanced polymorphisms. We welcome contributions from researchers at any career stage. Invited Speakers Meike Wittmann, Bielefeld University. Bielefeld. Germany Karl Grieshop, University of East Anglia. Norwich. England Organizers Dr. Hannah Augustijnen, University of Fribourg. Fribourg. Switzerland. Dr. Harshavardhan Thyagarajan, University of Fribourg. Fribourg. Switzerland. Best regards, Hannah Augustijnen Postdoctoral researcher Department of Biology University of Fribourg Switzerland Hannah.augustijnen@unifr.ch AUGUSTIJNEN Hannah (to subscribe/unsubscribe the EvolDir send mail to golding@mcmaster.ca)