TY - JOUR TI - Admixture of evolutionary rates across a butterfly hybrid zone AU - Xiong, Tianzhu AU - Li, Xueyan AU - Yago, Masaya AU - Mallet, James A2 - Matute, Daniel R A2 - Perry, George H A2 - Powell, Daniel L VL - 11 PY - 2022 DA - 2022/06/15 SP - e78135 C1 - eLife 2022;11:e78135 DO - 10.7554/eLife.78135 UR - https://doi.org/10.7554/eLife.78135 AB - Hybridization is a major evolutionary force that can erode genetic differentiation between species, whereas reproductive isolation maintains such differentiation. In studying a hybrid zone between the swallowtail butterflies Papilio syfanius and Papilio maackii (Lepidoptera: Papilionidae), we made the unexpected discovery that genomic substitution rates are unequal between the parental species. This phenomenon creates a novel process in hybridization, where genomic regions most affected by gene flow evolve at similar rates between species, while genomic regions with strong reproductive isolation evolve at species-specific rates. Thus, hybridization mixes evolutionary rates in a way similar to its effect on genetic ancestry. Using coalescent theory, we show that the rate-mixing process provides distinct information about levels of gene flow across different parts of genomes, and the degree of rate-mixing can be predicted quantitatively from relative sequence divergence (FST) between the hybridizing species at equilibrium. Overall, we demonstrate that reproductive isolation maintains not only genomic differentiation, but also the rate at which differentiation accumulates. Thus, asymmetric rates of evolution provide an additional signature of loci involved in reproductive isolation. KW - hybridization KW - reproductive isolation KW - molecular clock KW - gene flow JF - eLife SN - 2050-084X PB - eLife Sciences Publications, Ltd ER -