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Fitness of natural willow hybrids in a pioneer mosaic hybrid zone

Hybrid fitness is an important parameter to predict the evolutionary consequences of a hybridization event and to characterize hybrid zones. We studied fitness parameters of F(1) and later‐generation hybrids between the lowland species Salix purpurea and the alpine S. helvetica that have recently em...

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Autores principales: Gramlich, Susanne, Hörandl, Elvira
Formato: Online Artículo Texto
Lenguaje:English
Publicado: John Wiley and Sons Inc. 2016
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6093150/
https://www.ncbi.nlm.nih.gov/pubmed/30128118
http://dx.doi.org/10.1002/ece3.2470
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author Gramlich, Susanne
Hörandl, Elvira
author_facet Gramlich, Susanne
Hörandl, Elvira
author_sort Gramlich, Susanne
collection PubMed
description Hybrid fitness is an important parameter to predict the evolutionary consequences of a hybridization event and to characterize hybrid zones. We studied fitness parameters of F(1) and later‐generation hybrids between the lowland species Salix purpurea and the alpine S. helvetica that have recently emerged during colonization of an alpine glacier forefield. Fruit production (number of capsules per catkin and fruit set) did not differ between hybrids and parents, but the number of seeds per capsule of F(1) hybrids was slightly lower than that of later‐generation hybrids and of the parents. Germination rates and seedling growth were tested on three substrates (pH 4.5, 7.0, and 8.0). Germination rates of seeds collected from F(1) hybrids were lower on acid and neutral substrates, but equal at pH 8.0 compared to all other groups, while the seeds from later‐generation hybrids performed as well as the parents on all three substrates. In seedling growth, the colonizer S. purpurea performed better than all other taxa on all three substrates, while hybrids resembled the subalpine species S. helvetica. Results suggest that endogenous selection acts against F(1) hybrids, but favors fitter genotypes in later‐generation hybrids. Exogenous selection via soil pH appears to be weak during seedling establishment. The pioneer vegetation on the glacier forefield may offer sufficient niche space for hybrid seedlings. Owing to the relatively high fitness of the hybrids and the scattered distribution of hybrids and parental individuals on the glacier forefield, this hybrid zone can be assigned to a mosaic model, probably facilitating gene flow and introgression between the parental species. As establishment of the hybrid zone appears to be linked to a colonization process, we propose to call it a pioneer mosaic hybrid zone.
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spelling pubmed-60931502018-08-20 Fitness of natural willow hybrids in a pioneer mosaic hybrid zone Gramlich, Susanne Hörandl, Elvira Ecol Evol Original Research Hybrid fitness is an important parameter to predict the evolutionary consequences of a hybridization event and to characterize hybrid zones. We studied fitness parameters of F(1) and later‐generation hybrids between the lowland species Salix purpurea and the alpine S. helvetica that have recently emerged during colonization of an alpine glacier forefield. Fruit production (number of capsules per catkin and fruit set) did not differ between hybrids and parents, but the number of seeds per capsule of F(1) hybrids was slightly lower than that of later‐generation hybrids and of the parents. Germination rates and seedling growth were tested on three substrates (pH 4.5, 7.0, and 8.0). Germination rates of seeds collected from F(1) hybrids were lower on acid and neutral substrates, but equal at pH 8.0 compared to all other groups, while the seeds from later‐generation hybrids performed as well as the parents on all three substrates. In seedling growth, the colonizer S. purpurea performed better than all other taxa on all three substrates, while hybrids resembled the subalpine species S. helvetica. Results suggest that endogenous selection acts against F(1) hybrids, but favors fitter genotypes in later‐generation hybrids. Exogenous selection via soil pH appears to be weak during seedling establishment. The pioneer vegetation on the glacier forefield may offer sufficient niche space for hybrid seedlings. Owing to the relatively high fitness of the hybrids and the scattered distribution of hybrids and parental individuals on the glacier forefield, this hybrid zone can be assigned to a mosaic model, probably facilitating gene flow and introgression between the parental species. As establishment of the hybrid zone appears to be linked to a colonization process, we propose to call it a pioneer mosaic hybrid zone. John Wiley and Sons Inc. 2016-10-05 /pmc/articles/PMC6093150/ /pubmed/30128118 http://dx.doi.org/10.1002/ece3.2470 Text en © 2016 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd. This is an open access article under the terms of the http://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 Research
Gramlich, Susanne
Hörandl, Elvira
Fitness of natural willow hybrids in a pioneer mosaic hybrid zone
title Fitness of natural willow hybrids in a pioneer mosaic hybrid zone
title_full Fitness of natural willow hybrids in a pioneer mosaic hybrid zone
title_fullStr Fitness of natural willow hybrids in a pioneer mosaic hybrid zone
title_full_unstemmed Fitness of natural willow hybrids in a pioneer mosaic hybrid zone
title_short Fitness of natural willow hybrids in a pioneer mosaic hybrid zone
title_sort fitness of natural willow hybrids in a pioneer mosaic hybrid zone
topic Original Research
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6093150/
https://www.ncbi.nlm.nih.gov/pubmed/30128118
http://dx.doi.org/10.1002/ece3.2470
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