Check out our recent paper in the Journal of Evolutionary Biology: Physiological adaptation along environmental gradients and replicated hybrid zone structure in swordtails (Teleostei: Xiphophorus). Previous research in the Rosenthal lab at Texas A&M has shown that hybrids between X. malinche and X. birchmanni are favored by sexual selection, as females prefer to mate with hybrid males exhibiting a combination of parental traits. Nonetheless, hybrids are restricted to intermediate elevations along replicated river gradients and do not invade low elevation (X. birchmanni) and high elevation (X. malinche) parental populations. Our new paper shows that natural selection – particularly mediated by temperature gradients – stabilizes hybrid zone structure, as parentals are favored over hybrids at temperature extremes. Hence, while sexual selection seems to promote hybridization in this system, natural selection limits the distribution of hybrids and maintains hybrid zones at intermediate elevations.
Evolution in Extreme Environments
Tobler Lab at the University of Missouri—St. Louis
