title: Asymmetric Introgression in a Spotted Salamander Hybrid Zone.
abstract: Before the establishment of reproductive isolation, deeply diverged intraspecific lineages can experience complex genetic and behavioral interactions as they come into secondary contact. Divergent selective and demographic processes mediate gene flow among lineages, resulting in hybrid zones with complex biogeographic structure. Discordance in the biogeographic patterns of autosomal and maternally inherited loci provides a useful window to infer the processes mediating admixture and introgression across hybrid zones. Here, we sampled 489 genotypes across a hybrid zone between 2 phylogeographic lineages of the spotted salamander, Ambystoma maculatum, and characterize discordant patterns of nuclear and mitochondrial introgression across the contact boundary. Our results indicate asymmetric introgression of nuclear DNA beyond the contact boundary from the western to eastern lineage, with introgression of eastern mitochondrial DNA into the western lineage. We discuss alternative mechanisms for this pattern and attribute this result to neutral patterns of population expansion of the western lineage into the east in combination with female mate choice for larger-bodied western males. Our results underscore the complexity of interacting mechanisms that give rise to reproductive asymmetries in the earliest stages of the speciation process.
authors.affiliation: From the Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853 (Johnson, White, and Zamudio); Department of Biology, University of Oulu, P.O. Box 3000, Oulu 90014, Finland (White); and Illinois Natural History Survey, Prairie Research Institute, University of Illinois, Champaign, IL 61820 (Phillips). bbj23@cornell.edu.
authors.forename: Benjamin B
authors.initials: BB
authors.lastname: Johnson
authors.affiliation: From the Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853 (Johnson, White, and Zamudio); Department of Biology, University of Oulu, P.O. Box 3000, Oulu 90014, Finland (White); and Illinois Natural History Survey, Prairie Research Institute, University of Illinois, Champaign, IL 61820 (Phillips).
authors.forename: Thomas A
authors.initials: TA
authors.lastname: White
authors.affiliation: From the Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853 (Johnson, White, and Zamudio); Department of Biology, University of Oulu, P.O. Box 3000, Oulu 90014, Finland (White); and Illinois Natural History Survey, Prairie Research Institute, University of Illinois, Champaign, IL 61820 (Phillips).
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Phillips
authors.affiliation: From the Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853 (Johnson, White, and Zamudio); Department of Biology, University of Oulu, P.O. Box 3000, Oulu 90014, Finland (White); and Illinois Natural History Survey, Prairie Research Institute, University of Illinois, Champaign, IL 61820 (Phillips).
authors.forename: Kelly R
authors.initials: KR
authors.lastname: Zamudio
mesh_terms: D000557:Ambystoma / Q000235:genetics*; D000818:Animals; D001499:Bayes Theorem; D002467:Cell Nucleus / Q000235:genetics; D004272:DNA, Mitochondrial / Q000235:genetics; D017753:Ecosystem; D005260:Female; D051456:Gene Flow; D049810:Genetic Speciation; D005828:Genetics, Population; D005838:Genotype; D006824:Hybridization, Genetic; D007087:Illinois; D008297:Male; D018895:Microsatellite Repeats; D008923:Missouri; D008957:Models, Genetic; D058974:Phylogeography; D017422:Sequence Analysis, DNA
chemical_list: D004272:DNA, Mitochondrial
keywords: cline; hybrid zone; hybridization; mate choice; mitonuclear discordance