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Historic hybridization and persistence of a novel mito-nuclear combination in red-backed voles (genus Myodes).

Runck AM, Matocq MD, Cook JA - BMC Evol. Biol. (2009)

Bottom Line: The introgressant form is characterized by having mitochondrial haplotypes closely related to the northern M. rutilus on a nuclear background and morphological characteristics of southern M. gapperi.Introgression appears to have been historic as pure populations of M. rutilus are now isolated to the north from introgressants or pure M. gapperi by the LeConte Glacier.As we do not find pure M. rutilus or M. gapperi individuals throughout the distribution of the introgressant form, it appears that the introgressants are a self-sustaining entity not requiring continued hybridization between pure parental forms to generate this novel combination of characters.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biological Sciences, Idaho State University, Pocatello, Idaho 83209, USA. arunck2@unl.edu

ABSTRACT

Background: The role of hybridization in generating diversity in animals is an active area of discovery and debate. We assess hybridization across a contact zone of northern (Myodes rutilus) and southern (M. gapperi) red-backed voles using variation in skeletal features and both mitochondrial and nuclear loci. This transect extends approximately 550 km along the North Pacific Coast of North America and encompasses 26 populations (n = 485). We establish the history, geographic extent and directionality of hybridization, determine whether hybridization is ongoing, and assess the evolutionary stability of novel genomic combinations.

Results: Identification of M. rutilus and M. gapperi based on the degree of closure of the post-palatal bridge was concordant with the distribution of diagnostic nuclear MYH6 alleles; however, an 80 km zone of introgressed populations was identified. The introgressant form is characterized by having mitochondrial haplotypes closely related to the northern M. rutilus on a nuclear background and morphological characteristics of southern M. gapperi.

Conclusion: Introgression appears to have been historic as pure populations of M. rutilus are now isolated to the north from introgressants or pure M. gapperi by the LeConte Glacier. As we do not find pure M. rutilus or M. gapperi individuals throughout the distribution of the introgressant form, it appears that the introgressants are a self-sustaining entity not requiring continued hybridization between pure parental forms to generate this novel combination of characters.

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Mismatch distribution. Mismatch distribution for M. rutilus, M. gapperi and introgressants. The solid and dashed lines indicate observed and expected distributions, respectively.
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Figure 6: Mismatch distribution. Mismatch distribution for M. rutilus, M. gapperi and introgressants. The solid and dashed lines indicate observed and expected distributions, respectively.

Mentions: Values obtained through Fu's test of selective neutrality were largely negative and significantly different from zero (Table 2), which is expected for populations undergoing recent growth. However, negative values can also be a result of selection. The mismatch distributions were unimodal for M. rutilus, M. gapperi, and the introgressants, which is expected for populations undergoing sudden expansion or under certain selective regimes (Figure 6).


Historic hybridization and persistence of a novel mito-nuclear combination in red-backed voles (genus Myodes).

Runck AM, Matocq MD, Cook JA - BMC Evol. Biol. (2009)

Mismatch distribution. Mismatch distribution for M. rutilus, M. gapperi and introgressants. The solid and dashed lines indicate observed and expected distributions, respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2697987&req=5

Figure 6: Mismatch distribution. Mismatch distribution for M. rutilus, M. gapperi and introgressants. The solid and dashed lines indicate observed and expected distributions, respectively.
Mentions: Values obtained through Fu's test of selective neutrality were largely negative and significantly different from zero (Table 2), which is expected for populations undergoing recent growth. However, negative values can also be a result of selection. The mismatch distributions were unimodal for M. rutilus, M. gapperi, and the introgressants, which is expected for populations undergoing sudden expansion or under certain selective regimes (Figure 6).

Bottom Line: The introgressant form is characterized by having mitochondrial haplotypes closely related to the northern M. rutilus on a nuclear background and morphological characteristics of southern M. gapperi.Introgression appears to have been historic as pure populations of M. rutilus are now isolated to the north from introgressants or pure M. gapperi by the LeConte Glacier.As we do not find pure M. rutilus or M. gapperi individuals throughout the distribution of the introgressant form, it appears that the introgressants are a self-sustaining entity not requiring continued hybridization between pure parental forms to generate this novel combination of characters.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biological Sciences, Idaho State University, Pocatello, Idaho 83209, USA. arunck2@unl.edu

ABSTRACT

Background: The role of hybridization in generating diversity in animals is an active area of discovery and debate. We assess hybridization across a contact zone of northern (Myodes rutilus) and southern (M. gapperi) red-backed voles using variation in skeletal features and both mitochondrial and nuclear loci. This transect extends approximately 550 km along the North Pacific Coast of North America and encompasses 26 populations (n = 485). We establish the history, geographic extent and directionality of hybridization, determine whether hybridization is ongoing, and assess the evolutionary stability of novel genomic combinations.

Results: Identification of M. rutilus and M. gapperi based on the degree of closure of the post-palatal bridge was concordant with the distribution of diagnostic nuclear MYH6 alleles; however, an 80 km zone of introgressed populations was identified. The introgressant form is characterized by having mitochondrial haplotypes closely related to the northern M. rutilus on a nuclear background and morphological characteristics of southern M. gapperi.

Conclusion: Introgression appears to have been historic as pure populations of M. rutilus are now isolated to the north from introgressants or pure M. gapperi by the LeConte Glacier. As we do not find pure M. rutilus or M. gapperi individuals throughout the distribution of the introgressant form, it appears that the introgressants are a self-sustaining entity not requiring continued hybridization between pure parental forms to generate this novel combination of characters.

Show MeSH