Short- and long-term antagonistic selection explains dispersal polymorphism in the common lizard

Dispersal is a key process that shapes the dynamics, genetic structure and adaptive potential of natural populations, yet persistence of its polymorphism remains puzzling. Combining quantitative genetics with long-term field data from 20-year population monitoring of common lizards (Zootoca vivipara), we assessed the heritability, intragenerational and multi-generational selection of dispersal. We found both natal and adult dispersal to be weakly to moderately heritable (h2=0.1-0.22). Furthermore, we found that natal dispersal was subject to antagonistic selection pressures across timescales: dispersers experienced reduced individual fitness during their lifetime; however, their lineages persisted longer through generations, likely owing to competition-mediated kin selection within a lineage and resulting in neutral equilibrium. This antagonistic interplay between short- and long-term selection pressures explains how dispersal polymorphism is maintained in the studied population. Considering multi-generational fitness metrics reveals an evolutionary equilibrium that is obscured focusing on short-term perspectives. Therefore, our study highlights the importance of considering multiple generations to understand the persistence of phenotypic polymorphism.