Ecological Genetics of Sex-Chromosome Traits in the Tiger Swallowtail Butterfly Hybrid Zone

University Of Massachusetts Amherst, Amherst MA

Investigators

Abstract

9981608 Porter The tiger swallowtail butterfly species Papilio glaucus and P. canadensis meet in a narrow zone of hybridization across the eastern US. They differ in ecologically important traits, including the control of winter diapause and the mimicry (only by P. glaucus females) of a related, distasteful species. These traits are controlled by genes on the X- and Y-chromosomes. Theoretical advances in the biology of hybrid zones, such as this one, have allowed the measurement of the strength of natural selection acting on ecologically important traits, as well as the rate that other genes can slip through to the opposite species. The authors will use this theory to measure the strength of natural selection acting on diapause, wing coloration and other X- and Y-associated traits. They will do parallel field experiments to measure selection on these traits. Finally, they will measure the ability of this selection to block the spread of other genes between these hybridizing species. Sex chromosomes play a central role in biology and have several properties unique from other chromosomes, but biologists have few data from nature about how evolutionary forces affect sex-chromosome variation. The authors of this study exploit key features of the biology of these butterflies to study the evolutionary pressures acting on sex chromosomes and the spread of genes between related species.