title: Discordant divergence times among Z-chromosome regions between two ecologically distinct swallowtail butterfly species.
abstract: We investigate multilocus patterns of differentiation between parental populations of two swallowtail butterfly species that differ at a number of ecologically important sex-linked traits. Using a new coalescent-based approach, we show that there is significant heterogeneity in estimated divergence times among five Z-linked markers, rejecting a purely allopatric speciation model. We infer that the Z chromosome is a mosaic of regions that differ in the extent of historical gene flow, potentially due to isolating barriers that prevent the introgression of species-specific traits that result in hybrid incompatibilities. Surprisingly, a candidate region for a strong barrier to introgression, Ldh, does not show a significantly deeper divergence time than other markers on the Z chromosome. Our approach can be used to test alternative models of speciation and can potentially assign chronological order to the appearance of factors contributing to reproductive isolation between species.
authors: Section of Ecology, Behavior, and Evolution, Division of Biological Sciences, University of California, San Diego, La Jolla, California 92093, USA. asputnam@biomail.ucsd.edu
authors: Andrea S
authors: AS
authors: Putnam
authors: J Mark
authors: JM
authors: Scriber
authors: Peter
authors: P
authors: Andolfatto
mesh_terms: D000818:Animals; D001483:Base Sequence; D001499:Bayes Theorem; D002080:Butterflies / Q000235:genetics*; D002875:Chromosomes / Q000235:genetics*; D019143:Evolution, Molecular; D017344:Genes, Insect / Q000235:genetics; D049810:Genetic Speciation; D005828:Genetics, Population; D008957:Models, Genetic; D008969:Molecular Sequence Data; D011110:Polymorphism, Genetic; D017422:Sequence Analysis, DNA; D013045:Species Specificity; D013997:Time Factors