Mark Scriber is among the authors of a recent publication in PLoS Genetics entitled Sex Chromosome Moscaicism and Hybrid Speciation among Tiger Swallowtail Butterflies. The authors note, "Hybridization between two species may sometimes lead to the formation of a third species. While this phenomenon is of interest because it can generate new species from existing variation, it is rare in animals. Therefore, the factors responsible for the origin and maintenance of hybrid species are largely unknown. Here we show that the butterfly Papilio appalachiensis appears to be a hybrid species, which received nearly equal contributions to its genome from P. glaucus and P. canadensis...Historical climate change may have facilitated the origin of P. appalachiensis, which our data suggest coincided with the last interglacial period in North America. This example shows the importance of sex-linked traits and a potential role for natural selection in the origin and maintenance of hybrid species." View the paper.