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Genetic and morphological data demonstrate hybridization and backcrossing in a pair of salamanders at the far end of the speciation continuum

Deeply diverged yet hybridizing species provide a system to investigate the final stages of the speciation process. We study a hybridizing pair of salamander species—the morphologically and genetically drastically different newts Triturus cristatus and T. marmoratus—with a panel of 32 nuclear and mi...

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Autores principales: Arntzen, Jan W., Jehle, Robert, Wielstra, Ben
Formato: Online Artículo Texto
Lenguaje:English
Publicado: John Wiley and Sons Inc. 2021
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8674889/
https://www.ncbi.nlm.nih.gov/pubmed/34950229
http://dx.doi.org/10.1111/eva.13312
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author Arntzen, Jan W.
Jehle, Robert
Wielstra, Ben
author_facet Arntzen, Jan W.
Jehle, Robert
Wielstra, Ben
author_sort Arntzen, Jan W.
collection PubMed
description Deeply diverged yet hybridizing species provide a system to investigate the final stages of the speciation process. We study a hybridizing pair of salamander species—the morphologically and genetically drastically different newts Triturus cristatus and T. marmoratus—with a panel of 32 nuclear and mitochondrial genetic markers. Morphologically identified hybrids are mostly of the F(1) generation and mothered by T. cristatus. The sex ratio of the F(1) hybrid class is reciprocally skewed, with a preponderance of females in T. cristatus‐mothered hybrids and males in T. marmoratus‐mothered hybrids. This amounts to the Haldane effect operating in one direction of the cross. Deeper generation hybrids are occasionally produced, possibly including F(1) hybrid × backcross hybrid offspring. Interspecific gene flow is low, yet skewed toward T. cristatus. This asymmetry may be caused by hybrid zone movement, with the superseding species being predisposed to introgression. The persisting gene flow between deeply differentiated species supports the notion that full genetic isolation may be selected against. Conversely, published morphological data suggest that introgressive hybridization is detrimental, with digital malformations occurring more frequently in the area of sympatry. Finally, to assist field identification, both within the area of natural range overlap and concerning anthropogenic introductions elsewhere, we document the phenotypical variation of two generations of hybrids compared with both parental species. We suggest that fluctuating range boundaries, ecological segregation, cytonuclear incompatibilities and hybrid breakdown through Bateson–Dobzhansky–Muller incompatibilities all contribute to species integrity, despite incomplete isolation during secondary contact.
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spelling pubmed-86748892021-12-22 Genetic and morphological data demonstrate hybridization and backcrossing in a pair of salamanders at the far end of the speciation continuum Arntzen, Jan W. Jehle, Robert Wielstra, Ben Evol Appl Original Articles Deeply diverged yet hybridizing species provide a system to investigate the final stages of the speciation process. We study a hybridizing pair of salamander species—the morphologically and genetically drastically different newts Triturus cristatus and T. marmoratus—with a panel of 32 nuclear and mitochondrial genetic markers. Morphologically identified hybrids are mostly of the F(1) generation and mothered by T. cristatus. The sex ratio of the F(1) hybrid class is reciprocally skewed, with a preponderance of females in T. cristatus‐mothered hybrids and males in T. marmoratus‐mothered hybrids. This amounts to the Haldane effect operating in one direction of the cross. Deeper generation hybrids are occasionally produced, possibly including F(1) hybrid × backcross hybrid offspring. Interspecific gene flow is low, yet skewed toward T. cristatus. This asymmetry may be caused by hybrid zone movement, with the superseding species being predisposed to introgression. The persisting gene flow between deeply differentiated species supports the notion that full genetic isolation may be selected against. Conversely, published morphological data suggest that introgressive hybridization is detrimental, with digital malformations occurring more frequently in the area of sympatry. Finally, to assist field identification, both within the area of natural range overlap and concerning anthropogenic introductions elsewhere, we document the phenotypical variation of two generations of hybrids compared with both parental species. We suggest that fluctuating range boundaries, ecological segregation, cytonuclear incompatibilities and hybrid breakdown through Bateson–Dobzhansky–Muller incompatibilities all contribute to species integrity, despite incomplete isolation during secondary contact. John Wiley and Sons Inc. 2021-11-09 /pmc/articles/PMC8674889/ /pubmed/34950229 http://dx.doi.org/10.1111/eva.13312 Text en © 2021 The Authors. Evolutionary Applications published by John Wiley & Sons Ltd. https://creativecommons.org/licenses/by/4.0/This is an open access article under the terms of the http://creativecommons.org/licenses/by/4.0/ (https://creativecommons.org/licenses/by/4.0/) License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
spellingShingle Original Articles
Arntzen, Jan W.
Jehle, Robert
Wielstra, Ben
Genetic and morphological data demonstrate hybridization and backcrossing in a pair of salamanders at the far end of the speciation continuum
title Genetic and morphological data demonstrate hybridization and backcrossing in a pair of salamanders at the far end of the speciation continuum
title_full Genetic and morphological data demonstrate hybridization and backcrossing in a pair of salamanders at the far end of the speciation continuum
title_fullStr Genetic and morphological data demonstrate hybridization and backcrossing in a pair of salamanders at the far end of the speciation continuum
title_full_unstemmed Genetic and morphological data demonstrate hybridization and backcrossing in a pair of salamanders at the far end of the speciation continuum
title_short Genetic and morphological data demonstrate hybridization and backcrossing in a pair of salamanders at the far end of the speciation continuum
title_sort genetic and morphological data demonstrate hybridization and backcrossing in a pair of salamanders at the far end of the speciation continuum
topic Original Articles
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8674889/
https://www.ncbi.nlm.nih.gov/pubmed/34950229
http://dx.doi.org/10.1111/eva.13312
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