270T Poster - Population Genetics
Thursday June 09, 8:30 PM - 9:15 PM

Authors:
Tianzhu Xiong ¹; Xueyan Li ²; Masaya Yago ³; James Mallet ¹

Affiliations:
1) Harvard University, Cambridge, MA, USA; 2) Kunming Institute of Zoology, Chinese Academy of Science, Kunming, China; 3) The University Museum, The University of Tokyo, Tokyo, Japan

Keywords:
Speciation & hybridization

Hybridization is a major evolutionary force eroding genetic differentiation between species, whereas reproductive isolation maintains such differentiation. In studying a hybrid zone between the swallowtail butterflies Papilio syfanius and Papilio maackii, 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 a similar rate across species, while genomic regions with greater reproductive isolation evolve at divergent rates. Thus, hybridization mixes evolutionary rates in a way similar to genetic admixture. 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 maintenance of divergent substitution rates can be predicted quantitatively from relative sequence divergence (F_ST) between the hybridizing species at equilibrium. A corollary is that divergent rates will be maintained in regions linked to barrier loci. Overall, we demonstrate that reproductive isolation maintains not only the final outcome of genomic differentiation, but also the rate at which differentiation accumulates. This new information also suggests that the separation of evolutionary rates co-localizes with the separation of gene pools between genomes of incipient species.