Genomic variation across two barn swallow hybrid zones reveals traits associated with divergence in sympatry and allopatry.
Mol Ecol
; 26(20): 5676-5691, 2017 Oct.
Article
em En
| MEDLINE
| ID: mdl-28777875
ABSTRACT
Hybrid zones are geographic regions where isolating barriers between divergent populations are challenged by admixture. Identifying factors that facilitate or inhibit hybridization in sympatry can illuminate the processes that maintain those reproductive barriers. We analysed patterns of hybridization and phenotypic variation across two newly discovered hybrid zones between three subspecies of barn swallow (Hirundo rustica). These subspecies differ in ventral coloration and wing length, traits that are targets of sexual and natural selection, respectively, and are associated with genome-wide differentiation in allopatry. We tested the hypothesis that the degree of divergence in these traits is associated with the extent of hybridization in secondary contact. We applied measures of population structure based on >23,000 SNPs to confirm that named subspecies correspond to distinct genomic clusters, and assessed coincidence between geographic clines for ancestry and phenotype. Although gene flow was ongoing across both hybrid zones and pairwise FST between subspecies was extremely low, we found striking differences in the extent of hybridization. In the more phenotypically differentiated subspecies pair, clines for ancestry, wing length and ventral coloration were steep and coincident, suggestive of strong isolation and, potentially, selection associated with phenotype. In the less phenotypically differentiated pair, gene flow and phenotypic variation occurred over a wide geographic span, indicative of weaker isolation. Traits associated with genome-wide differentiation in allopatry may thus also contribute to isolation in sympatry. We discuss potentially important additional roles for evolutionary history and ecology in shaping variation in the extent hybridization between closely related pairs of subspecies.
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Assunto principal:
Andorinhas
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Fluxo Gênico
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Simpatria
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Genética Populacional
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Hibridização Genética
Tipo de estudo:
Prognostic_studies
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Risk_factors_studies
Limite:
Animals
Idioma:
En
Ano de publicação:
2017
Tipo de documento:
Article