Patterns of Performance Variation Between Animal Hybrids and their Parents: A Meta-analysis

Abstract Hybridization is a widespread phenomenon in animals, and hybrid heterosis/breakdown could be key processes determining the evolutionary dynamics of hybrids. Indeed, hybrids are not consistently disadvantaged compared to parental lineages, as was historically assumed. Multiple lead performance differences between lineages their Despite many studies evaluated hybrids, quantitative synthesis required assess general pattern. Here we used meta-analytic meta-regression approaches quantify fitness identify possible that these differences. Specifically, tested biological methodological parameters determine lineages. Hybrid extremely variable across studies, being often significantly higher or lower mean parents. Nevertheless, averaged similar with related how assessed. Genetic divergence approach were most strongly variation performance. Performance for distantly Furthermore, study settings use imprecise identification (e.g. morphology-based) can bias assessments Studies performed on wild populations using genetic detected more decreased performance, laboratory studies. We highlight importance appropriate realistic understanding impacts hybridization.