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Caeiro-Dias G, Brelsford A, Meneses-Ribeiro M, Crochet PA, Pinho C. Hybridization in late stages of speciation: Strong but incomplete genome-wide reproductive isolation and 'large Z-effect' in a moving hybrid zone. Mol Ecol 2023. [PMID: 37316984 DOI: 10.1111/mec.17035] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2022] [Revised: 04/27/2023] [Accepted: 05/12/2023] [Indexed: 06/16/2023]
Abstract
In organisms reproducing sexually, speciation occurs when increasing divergence results in pre- or post-zygotic reproductive isolation between lineages. Studies focusing on reproductive isolation origin in early stages of speciation are common and many rely on genomic scans to infer introgression providing limited information on the genomic architecture of reproductive isolation long-term maintenance. This study analyses a natural hybrid zone between two species in a late stage of speciation. We used ddRADseq genotyping in the contact between Podarcis bocagei and P. carbonelli to examine admixture extent, analyse hybrid zone stability and assess genome-wide variation in selection against introgression. We confirmed strong but incomplete reproductive isolation in a bimodal hybrid zone. New findings revealed population genetic structure within P. carbonelli in the contact zone; geographical and genomic clines analysis suggested strong selection against gene flow, but a relatively small proportion of the loci can introgress, mostly within the narrow contact zone. However, geographical clines revealed that a few introgressed loci show signs of potential positive selection, particularly into P. bocagei. Geographical clines also detected a signal of hybrid zone movement towards P. bocagei distribution. Genomic cline analysis revealed heterogeneous patterns of introgression among loci within the syntopy zone, but the majority maintain a strong association with the genomic background of origin. However, incongruences between both cline approaches were found, potentially driven by confounding effects on genomic clines. Last, an important role of the Z chromosome in reproductive isolation is suggested. Importantly, overall patterns of restricted introgression seem to result from numerous strong intrinsic barriers across the genome.
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Affiliation(s)
- Guilherme Caeiro-Dias
- CIBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos, InBIO Laboratório Associado, Universidade do Porto, Vairão, Portugal
- Departamento de Biologia, Faculdade de Ciências, Universidade do Porto, Porto, Portugal
- CEFE, CNRS, Univ Montpellier, EPHE, IRD, Montpellier, France
| | - Alan Brelsford
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland
- Biology Department, University of California Riverside, Riverside, California, USA
| | - Mariana Meneses-Ribeiro
- CIBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos, InBIO Laboratório Associado, Universidade do Porto, Vairão, Portugal
- Departamento de Biologia, Faculdade de Ciências, Universidade do Porto, Porto, Portugal
- BIOPOLIS Program in Genomics, Biodiversity and Land Planning, CIBIO, Vairão, Portugal
| | - Pierre-André Crochet
- Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland
| | - Catarina Pinho
- CIBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos, InBIO Laboratório Associado, Universidade do Porto, Vairão, Portugal
- BIOPOLIS Program in Genomics, Biodiversity and Land Planning, CIBIO, Vairão, Portugal
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Hancock ZB, Toczydlowski RH, Bradburd GS. A spatial approach to jointly estimate Wright's neighborhood size and long-term effective population size. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.10.532094. [PMID: 36945591 PMCID: PMC10029013 DOI: 10.1101/2023.03.10.532094] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/14/2023]
Abstract
Spatially continuous patterns of genetic differentiation, which are common in nature, are often poorly described by existing population genetic theory or methods that assume panmixia or discrete, clearly definable populations. There is therefore a need for statistical approaches in population genetics that can accommodate continuous geographic structure, and that ideally use georeferenced individuals as the unit of analysis, rather than populations or subpopulations. In addition, researchers are often interested describing the diversity of a population distributed continuously in space, and this diversity is intimately linked to the dispersal potential of the organism. A statistical model that leverages information from patterns of isolation-by-distance to jointly infer parameters that control local demography (such as Wright's neighborhood size), and the long-term effective size (Ne) of a population would be useful. Here, we introduce such a model that uses individual-level pairwise genetic and geographic distances to infer Wright's neighborhood size and long-term Ne. We demonstrate the utility of our model by applying it to complex, forward-time demographic simulations as well as an empirical dataset of the Red Sea clownfish (Amphiprion bicinctus). The model performed well on simulated data relative to alternative approaches and produced reasonable empirical results given the natural history of clownfish. The resulting inferences provide important insights into the population genetic dynamics of spatially structure populations.
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Affiliation(s)
- Zachary B. Hancock
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI 481103, USA
| | | | - Gideon S. Bradburd
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI 481103, USA
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