Funding provided by University of Maryland Program in Behavior, Ecology, Evolution, and Systematics, Smithsonian Ornithology, and Smithsonian Institution Science Endowments Program. NSF grants DEB0228675 and DEB0733029 and the NMNH Frontiers in Phylogenetics Program provided research assistantships.
Genomic variation in cline shape across a hybrid zone
Article first published online: 1 OCT 2012
© 2012 The Authors. Published by Blackwell Publishing Ltd. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Ecology and Evolution
Volume 2, Issue 11, pages 2737–2748, November 2012
How to Cite
Ecology and Evolution 2012; 2(11): 2737–2748
- Issue published online: 8 NOV 2012
- Article first published online: 1 OCT 2012
- Manuscript Accepted: 20 AUG 2012
- Manuscript Revised: 13 AUG 2012
- Manuscript Received: 6 AUG 2012
- University of Maryland Program in Behavior, Ecology, Evolution, and Systematics, Smithsonian Ornithology, Smithsonian Institution National Museum of Natural History Vertebrate Zoology. Grant Numbers: DEB0228675, DEB0733029
- AFLP ;
- gene flow;
- mitochondrial DNA;
- Pipilo maculatus ;
- Pipilo ocai ;
- tension zone model;
Hybrid zones are unique biological interfaces that reveal both population level and species level evolutionary processes. A genome-scale approach to assess gene flow across hybrid zones is vital, and now possible. In Mexican towhees (genus Pipilo), several morphological hybrid gradients exist. We completed a genome survey across one such gradient (9 populations, 140 birds) using mitochondrial DNA, 28 isozyme, and 377 AFLP markers. To assess variation in introgression among loci, cline parameters (i.e., width, center) for the 61 clinally varying loci were estimated and compiled into genomic distributions for tests against three empirical models spanning the range of observed cline shape. No single model accounts for observed variation in cline shape among loci. Numerous backcross individuals near the gradient center confirm a hybrid origin for these populations, contrary to a previous hypothesis based on social mimicry and character displacement. In addition, the observed variation does not bin into well-defined categories of locus types (e.g., neutral vs. highly selected). Our multi-locus analysis reveals cross-genomic variation in selective constraints on gene flow and locus-specific flexibility in the permeability of the interspecies membrane.