1Strong selection can cause rapid evolutionary change, but temporal fluctuations in the form, 2 direction and intensity of selection can limit net evolutionary change over longer time periods. 3 Fluctuating selection could affect molecular diversity levels and the evolution of plasticity 4 and ecological specialization. Nonetheless, this phenomenon remains understudied, in part 5 because of analytical limitations and the general difficulty of detecting selection that does not 6 occur in a consistent manner. Herein, I fill this analytical gap by presenting an approximate 7 Bayesian computation (ABC) method to detect and quantify fluctuating selection on poly-8 genic traits from population-genomic time-series data. I propose a model for environment-9 dependent phenotypic selection. The evolutionary genetic consequences of selection are then 10 modeled based on a genotype-phenotype map. Using simulations, I show that the proposed 11 method generates accurate and precise estimates of selection when the generative model for 12 the data is similar to the model assumed by the method. Performance of the method when 13 applied to an evolve-and-resequence study of host adaptation in the cowpea seed beetle (Cal-14 losobruchus maculatus) was more idiosyncratic and depended on specific analytical choices.
15Despite some limitations, these results suggest the proposed method provides a powerful 16 approach to connect causes of (variable) selection to traits and genome-wide patterns of 17 evolution. Documentation and open source computer software (fsabc) implementing this 18 method are available from GitHub (https://github.com/zgompert/fsabc.git).19 20 mate Bayesian computation, computational statistics, Callosobruchus macula-21 tus 22 selection on a trait is intense (Walsh & Lynch, 2018). A general approach to overcome this 76 limitation was suggested by Berg & Coop (2014) (also see Josephs et al., 2019). Specifically, 77 polygenic adaptation can be inferred by incorporating genotype-phenotype associations from 78 genome-wide association studies (GWAS) in population-genomic tests for selection. This 79 makes it possible to accumulate evidence of selection across trait-associated loci, and thus 80 detect selection even when none of the individual loci experience strong selection. Thus far, 81 this analytical framework has mostly been applied to static population-genomic data sets, 82 and not to detect fluctuating selection from temporal data. 83 Herein, I fill this analytical gap by presenting an approximate Bayesian computation 84 (ABC) method to detect and quantify fluctuating selection on polygenic traits from time-85 series data. With this method, phenotypic selection is modeled as an explicit function of the 86 state of the environment (similar to Gompert, 2016). The population-genomic consequences 87 of selection are then modeled based on estimated genotype-phenotype associations (similar 88 to Berg & Coop, 2014). This allows inferences to be informed by patterns of change across 89 multiple genetic loci, populations, ...