Kasha Strickland, Blake Matthews, Zophonias Jonsson, Bjarni Kristjansson, Joseph Phillips, Arni Einarsson, Katja Rasanen

Identifying microevolutionary change in the wild requires linking trait change to shifts in allele fre-quencies, but existing approaches poorly account for different modes of selection that act simulta-neously on correlated traits. Using an integrative phenome-genome time-series dataset collected on wild threespine stickleback (Gasterosteus aculeatus), we identified how different modes of selec-tion (directional, balancing, and episodic) drive trait change over time. Specifically, we show that dietary traits in our population changed linearly by an average of 16% across 10 generations, which was linked to changes in both genomic breeding values and allele frequencies at quantitative trait loci for dietary traits. Importantly, allele frequencies at quantitative trait loci were changing at a rate greater than expected under neutrality, suggesting that dietary traits were under directional selec-tion. We further show that swimming-related traits may be under episodic selection caused by an extreme population crash. Our study provides a unique empirical demonstration of microevolution in a wild population in which multiple modes of selection act simultaneously on different traits, which likely has important downstream consequences for the evolution of correlated traits.