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Patterns of genetic, phenotypic, and acoustic variation across a chiffchaff ( Phylloscopus collybita abietinus/tristis ) hybrid zone

View Article: PubMed Central - PubMed

ABSTRACT

Characterizing patterns of evolution of genetic and phenotypic divergence between incipient species is essential to understand how evolution of reproductive isolation proceeds. Hybrid zones are excellent for studying such processes, as they provide opportunities to assess trait variation in individuals with mixed genetic background and to quantify gene flow across different genomic regions. Here, we combine plumage, song, mtDNA and whole‐genome sequence data and analyze variation across a sympatric zone between the European and the Siberian chiffchaff (Phylloscopus collybita abietinus/tristis) to study how gene exchange between the lineages affects trait variation. Our results show that chiffchaff within the sympatric region show more extensive trait variation than allopatric birds, with a large proportion of individuals exhibiting intermediate phenotypic characters. The genomic differentiation between the subspecies is lower in sympatry than in allopatry and sympatric birds have a mix of genetic ancestry indicating extensive ongoing and past gene flow. Patterns of phenotypic and genetic variation also vary between regions within the hybrid zone, potentially reflecting differences in population densities, age of secondary contact, or differences in mate recognition or mate preference. The genomic data support the presence of two distinct genetic clades corresponding to allopatric abietinus and tristis and that genetic admixture is the force underlying trait variation in the sympatric region—the previously described subspecies (“fulvescens”) from the region is therefore not likely a distinct taxon. In addition, we conclude that subspecies identification based on appearance is uncertain as an individual with an apparently distinct phenotype can have a considerable proportion of the genome composed of mixed alleles, or even a major part of the genome introgressed from the other subspecies. Our results provide insights into the dynamics of admixture across subspecies boundaries and have implications for understanding speciation processes and for the identification of specific chiffchaff individuals based on phenotypic characters.

No MeSH data available.


Distribution of scored mitochondrial haplotypes across the European and Siberian chiffchaff ranges with particular focus on the sympatric zone. The two identified tristis haplotypes that only differ at a single nucleotide position have been grouped and are presented in yellow, and the diagnostic abietinus haplotype is given in green
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ece32782-fig-0001: Distribution of scored mitochondrial haplotypes across the European and Siberian chiffchaff ranges with particular focus on the sympatric zone. The two identified tristis haplotypes that only differ at a single nucleotide position have been grouped and are presented in yellow, and the diagnostic abietinus haplotype is given in green

Mentions: We obtained high‐quality data for the mitochondrial CytB gene for three positions (SNPs) using restriction analysis in 193 individuals of allopatric abietinus (n = 12) and tristis (n = 37) and birds from both the northern (n = 53) and the southern part (n = 91) of the sympatric zone. Allopatric birds all had distinct mtDNA haplotypes (a single haplotype in Europe and a single haplotype in Siberia). Both in the northern and in the southern sympatric regions, we observed a mixture of these haplotypes, along with a previously identified third haplotype (tristis‐2, haplotype found in 21 birds) that differs from the diagnostic tristis haplotype found in allopatry at a single nucleotide position (Marova et al., 2009). Distribution of haplotypes within the geographic regions are shown in Figure 1 where the two similar tristis haplotypes are merged in a single group.


Patterns of genetic, phenotypic, and acoustic variation across a chiffchaff ( Phylloscopus collybita abietinus/tristis ) hybrid zone
Distribution of scored mitochondrial haplotypes across the European and Siberian chiffchaff ranges with particular focus on the sympatric zone. The two identified tristis haplotypes that only differ at a single nucleotide position have been grouped and are presented in yellow, and the diagnostic abietinus haplotype is given in green
© Copyright Policy - creativeCommonsBy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC5383471&req=5

ece32782-fig-0001: Distribution of scored mitochondrial haplotypes across the European and Siberian chiffchaff ranges with particular focus on the sympatric zone. The two identified tristis haplotypes that only differ at a single nucleotide position have been grouped and are presented in yellow, and the diagnostic abietinus haplotype is given in green
Mentions: We obtained high‐quality data for the mitochondrial CytB gene for three positions (SNPs) using restriction analysis in 193 individuals of allopatric abietinus (n = 12) and tristis (n = 37) and birds from both the northern (n = 53) and the southern part (n = 91) of the sympatric zone. Allopatric birds all had distinct mtDNA haplotypes (a single haplotype in Europe and a single haplotype in Siberia). Both in the northern and in the southern sympatric regions, we observed a mixture of these haplotypes, along with a previously identified third haplotype (tristis‐2, haplotype found in 21 birds) that differs from the diagnostic tristis haplotype found in allopatry at a single nucleotide position (Marova et al., 2009). Distribution of haplotypes within the geographic regions are shown in Figure 1 where the two similar tristis haplotypes are merged in a single group.

View Article: PubMed Central - PubMed

ABSTRACT

Characterizing patterns of evolution of genetic and phenotypic divergence between incipient species is essential to understand how evolution of reproductive isolation proceeds. Hybrid zones are excellent for studying such processes, as they provide opportunities to assess trait variation in individuals with mixed genetic background and to quantify gene flow across different genomic regions. Here, we combine plumage, song, mtDNA and whole‐genome sequence data and analyze variation across a sympatric zone between the European and the Siberian chiffchaff (Phylloscopus collybita abietinus/tristis) to study how gene exchange between the lineages affects trait variation. Our results show that chiffchaff within the sympatric region show more extensive trait variation than allopatric birds, with a large proportion of individuals exhibiting intermediate phenotypic characters. The genomic differentiation between the subspecies is lower in sympatry than in allopatry and sympatric birds have a mix of genetic ancestry indicating extensive ongoing and past gene flow. Patterns of phenotypic and genetic variation also vary between regions within the hybrid zone, potentially reflecting differences in population densities, age of secondary contact, or differences in mate recognition or mate preference. The genomic data support the presence of two distinct genetic clades corresponding to allopatric abietinus and tristis and that genetic admixture is the force underlying trait variation in the sympatric region—the previously described subspecies (“fulvescens”) from the region is therefore not likely a distinct taxon. In addition, we conclude that subspecies identification based on appearance is uncertain as an individual with an apparently distinct phenotype can have a considerable proportion of the genome composed of mixed alleles, or even a major part of the genome introgressed from the other subspecies. Our results provide insights into the dynamics of admixture across subspecies boundaries and have implications for understanding speciation processes and for the identification of specific chiffchaff individuals based on phenotypic characters.

No MeSH data available.