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Population Structure of a Widespread Species under Balancing Selection: The Case of Arbutus unedo L.

Arbutus unedo L. is an evergreen shrub with a circum-Mediterranean distribution that also reaches the Eurosiberian region in northern Iberia, Atlantic France, and a disjunct population in southern Ireland. Due to the variety of climatic conditions across its distribution range, the populations of A....

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Autores principales: Santiso, Xabier, Lopez, Lua, Retuerto, Rubén, Barreiro, Rodolfo
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Frontiers Media S.A. 2016
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4710743/
https://www.ncbi.nlm.nih.gov/pubmed/26793231
http://dx.doi.org/10.3389/fpls.2015.01264
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author Santiso, Xabier
Lopez, Lua
Retuerto, Rubén
Barreiro, Rodolfo
author_facet Santiso, Xabier
Lopez, Lua
Retuerto, Rubén
Barreiro, Rodolfo
author_sort Santiso, Xabier
collection PubMed
description Arbutus unedo L. is an evergreen shrub with a circum-Mediterranean distribution that also reaches the Eurosiberian region in northern Iberia, Atlantic France, and a disjunct population in southern Ireland. Due to the variety of climatic conditions across its distribution range, the populations of A. unedo were expected to display local adaptation. Conversely, common garden experiments revealed that diverse genotypes from a range of provenances produce similar phenotypes through adaptive plasticity, suggesting the action of stabilizing selection across its climatically heterogeneous range. Nonetheless, since a uniform response might also result from extensive gene flow, we have inferred the population structure of A. unedo and assessed whether its extended and largely one-dimensional range influences gene flow with the help of AFLP genotypes for 491 individuals from 19 populations covering the whole range of the species. As we had anticipated, gene flow is restricted in A. unedo, providing further support to the hypothesis that stabilizing selection is the most likely explanation for the homogeneous phenotypes along the range. The Euro-Siberian populations were not particularly isolated from the Mediterranean. Instead, there was a distinct genetic divide between the populations around the Mediterranean Sea and those sampled along Atlantic coasts from northern Africa up to Ireland. This genetic structure suggests the action of historic rather than biogeographic factors as it seems consistent with a scenario of independent glacial refugia in the Atlantic and Mediterranean portions of the range of A. unedo. Genetic exchange was likewise restricted within each set of populations. Nevertheless, isolation-by-distance (IBD) was stronger, and F(ST) increased faster with distance, along the Atlantic, suggesting that gene flow might be larger among Mediterranean populations. Genetic diversity was significantly lower in NW Iberia and Ireland than in other populations whereas Ireland was more closely related to populations in NW Iberia than to a population in Atlantic France, suggesting a postglacial stepping-stone colonization of the Atlantic coast. Altogether, our results show that stabilizing selection is able to homogenize the phenotypic response even when population structure is strong, gene flow is constrained, and the phylogeographic past is complex.
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spelling pubmed-47107432016-01-20 Population Structure of a Widespread Species under Balancing Selection: The Case of Arbutus unedo L. Santiso, Xabier Lopez, Lua Retuerto, Rubén Barreiro, Rodolfo Front Plant Sci Genetics Arbutus unedo L. is an evergreen shrub with a circum-Mediterranean distribution that also reaches the Eurosiberian region in northern Iberia, Atlantic France, and a disjunct population in southern Ireland. Due to the variety of climatic conditions across its distribution range, the populations of A. unedo were expected to display local adaptation. Conversely, common garden experiments revealed that diverse genotypes from a range of provenances produce similar phenotypes through adaptive plasticity, suggesting the action of stabilizing selection across its climatically heterogeneous range. Nonetheless, since a uniform response might also result from extensive gene flow, we have inferred the population structure of A. unedo and assessed whether its extended and largely one-dimensional range influences gene flow with the help of AFLP genotypes for 491 individuals from 19 populations covering the whole range of the species. As we had anticipated, gene flow is restricted in A. unedo, providing further support to the hypothesis that stabilizing selection is the most likely explanation for the homogeneous phenotypes along the range. The Euro-Siberian populations were not particularly isolated from the Mediterranean. Instead, there was a distinct genetic divide between the populations around the Mediterranean Sea and those sampled along Atlantic coasts from northern Africa up to Ireland. This genetic structure suggests the action of historic rather than biogeographic factors as it seems consistent with a scenario of independent glacial refugia in the Atlantic and Mediterranean portions of the range of A. unedo. Genetic exchange was likewise restricted within each set of populations. Nevertheless, isolation-by-distance (IBD) was stronger, and F(ST) increased faster with distance, along the Atlantic, suggesting that gene flow might be larger among Mediterranean populations. Genetic diversity was significantly lower in NW Iberia and Ireland than in other populations whereas Ireland was more closely related to populations in NW Iberia than to a population in Atlantic France, suggesting a postglacial stepping-stone colonization of the Atlantic coast. Altogether, our results show that stabilizing selection is able to homogenize the phenotypic response even when population structure is strong, gene flow is constrained, and the phylogeographic past is complex. Frontiers Media S.A. 2016-01-13 /pmc/articles/PMC4710743/ /pubmed/26793231 http://dx.doi.org/10.3389/fpls.2015.01264 Text en Copyright © 2016 Santiso, Lopez, Retuerto and Barreiro. http://creativecommons.org/licenses/by/4.0/ This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
spellingShingle Genetics
Santiso, Xabier
Lopez, Lua
Retuerto, Rubén
Barreiro, Rodolfo
Population Structure of a Widespread Species under Balancing Selection: The Case of Arbutus unedo L.
title Population Structure of a Widespread Species under Balancing Selection: The Case of Arbutus unedo L.
title_full Population Structure of a Widespread Species under Balancing Selection: The Case of Arbutus unedo L.
title_fullStr Population Structure of a Widespread Species under Balancing Selection: The Case of Arbutus unedo L.
title_full_unstemmed Population Structure of a Widespread Species under Balancing Selection: The Case of Arbutus unedo L.
title_short Population Structure of a Widespread Species under Balancing Selection: The Case of Arbutus unedo L.
title_sort population structure of a widespread species under balancing selection: the case of arbutus unedo l.
topic Genetics
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4710743/
https://www.ncbi.nlm.nih.gov/pubmed/26793231
http://dx.doi.org/10.3389/fpls.2015.01264
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