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Genomic replacement of native Cobitis lutheri with introduced C. tetralineata through a hybrid swarm following the artificial connection of river systems.

Kwan YS, Ko MH, Won YJ - Ecol Evol (2014)

Bottom Line: The construction of water canals about 80 years ago has unidirectionally introduced C. tetralineata into the native habitat of C. lutheri, and then these species have hybridized in the main stream section of the Dongjin River.According to the divergence population genetic analyses of DNA sequence data, the two species diverged about 3.3 million years ago, which is interestingly coincident with the unprecedented paleoceanographic change that caused isolations of the paleo-river systems in northeast Asia due to sea-level changes around the late Pliocene.In addition, mating experiments indicated that there is no discernible reproductive isolation between them.

View Article: PubMed Central - PubMed

Affiliation: Division of EcoScience, Ewha Womans University 52, Ewhayeodae-gil, Seodaemun-gu, Seoul, Korea.

ABSTRACT
River connections via artificial canals will bring about secondary contacts between previously isolated fish species. Here, we present a genetic consequence of such a secondary contact between Cobitis fish species, C. lutheri in the Dongjin River, and C. tetralineata in the Seomjin River in Korea. The construction of water canals about 80 years ago has unidirectionally introduced C. tetralineata into the native habitat of C. lutheri, and then these species have hybridized in the main stream section of the Dongjin River. According to the divergence population genetic analyses of DNA sequence data, the two species diverged about 3.3 million years ago, which is interestingly coincident with the unprecedented paleoceanographic change that caused isolations of the paleo-river systems in northeast Asia due to sea-level changes around the late Pliocene. Multilocus genotypic data of nine microsatellites and three nuclear loci revealed an extensively admixed structure in the hybrid zone with a high proportion of various post-F1 hybrids. Surprisingly, pure native C. lutheri was absent in the hybrid zone in contrast to the 7% of pure C. tetralineata. Such a biased proportion must have resulted from the dominant influence of continually introducing C. tetralineata on the native C. lutheri which has no supply of natives from other tributaries to the hybrid zone due to numerous low-head dams. In addition, mating experiments indicated that there is no discernible reproductive isolation between them. All the results suggest that the gene pool of native C. lutheri is being rapidly replaced by that of continually introducing C. tetralineata through a hybrid swarm for the last 80 years, which will ultimately lead to the genomic extinction of natives in this hybrid zone.

No MeSH data available.


Marginal posterior probability, P, of (A) effective population sizes (q), (B) the splitting time (t) in years between C. lutheri and C. tetralineata, and (C) population migration rates (2Nm) estimated by IMa2.
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fig03: Marginal posterior probability, P, of (A) effective population sizes (q), (B) the splitting time (t) in years between C. lutheri and C. tetralineata, and (C) population migration rates (2Nm) estimated by IMa2.

Mentions: To infer the divergence process of the allopatric C. lutheri and C. tetralineata, we estimated population demographic parameters for the Mangyeong and Seomjin River populations (Fig. 3). We used 278 bp of ENC1, 554 bp of Ptr, and 240 bp of SH3PX3 for this analysis after excluding recombinant blocks of DNA segments. The substitution rates (substitutions/site/million years) at each locus calculated using BEAST (Table 2) were employed as mutation rates for the IMa2 analysis. The IMa2 analysis resulted in an estimate of the effective population size of C. lutheri in the Mangyeong River (mean of 140,000 with 95% confidence interval (CI) of 82,000–218,000) that was almost three times higher than that of C. tetralineata (mean of 42,000 with 95% CI of 20,000–76,000). The splitting time between C. lutheri and C. tetralineata was estimated to be approximately 3.3 MYA (95% CI of 0.9–6.6). The population migration rates per generation (2Nm) between C. lutheri and C. tetralineata were very close to zero (from C. lutheri to C. tetralineata, mean of 0.056 with 95% CI of 0.001–0.202; from C. tetralineata to C. lutheri, mean of 0.053 with 95% CI of 0.002–0.167). The full model of five demographic parameters (θ1θ2θAm1 m2) was not rejected by the three nested models (θ1θ2θAm1 = 0 m2; θ1θ2θAm1 m2 = 0; and θ1θ2θAm1 = m2). All the P-values were near one for each alternative nested model.


Genomic replacement of native Cobitis lutheri with introduced C. tetralineata through a hybrid swarm following the artificial connection of river systems.

Kwan YS, Ko MH, Won YJ - Ecol Evol (2014)

Marginal posterior probability, P, of (A) effective population sizes (q), (B) the splitting time (t) in years between C. lutheri and C. tetralineata, and (C) population migration rates (2Nm) estimated by IMa2.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4020703&req=5

fig03: Marginal posterior probability, P, of (A) effective population sizes (q), (B) the splitting time (t) in years between C. lutheri and C. tetralineata, and (C) population migration rates (2Nm) estimated by IMa2.
Mentions: To infer the divergence process of the allopatric C. lutheri and C. tetralineata, we estimated population demographic parameters for the Mangyeong and Seomjin River populations (Fig. 3). We used 278 bp of ENC1, 554 bp of Ptr, and 240 bp of SH3PX3 for this analysis after excluding recombinant blocks of DNA segments. The substitution rates (substitutions/site/million years) at each locus calculated using BEAST (Table 2) were employed as mutation rates for the IMa2 analysis. The IMa2 analysis resulted in an estimate of the effective population size of C. lutheri in the Mangyeong River (mean of 140,000 with 95% confidence interval (CI) of 82,000–218,000) that was almost three times higher than that of C. tetralineata (mean of 42,000 with 95% CI of 20,000–76,000). The splitting time between C. lutheri and C. tetralineata was estimated to be approximately 3.3 MYA (95% CI of 0.9–6.6). The population migration rates per generation (2Nm) between C. lutheri and C. tetralineata were very close to zero (from C. lutheri to C. tetralineata, mean of 0.056 with 95% CI of 0.001–0.202; from C. tetralineata to C. lutheri, mean of 0.053 with 95% CI of 0.002–0.167). The full model of five demographic parameters (θ1θ2θAm1 m2) was not rejected by the three nested models (θ1θ2θAm1 = 0 m2; θ1θ2θAm1 m2 = 0; and θ1θ2θAm1 = m2). All the P-values were near one for each alternative nested model.

Bottom Line: The construction of water canals about 80 years ago has unidirectionally introduced C. tetralineata into the native habitat of C. lutheri, and then these species have hybridized in the main stream section of the Dongjin River.According to the divergence population genetic analyses of DNA sequence data, the two species diverged about 3.3 million years ago, which is interestingly coincident with the unprecedented paleoceanographic change that caused isolations of the paleo-river systems in northeast Asia due to sea-level changes around the late Pliocene.In addition, mating experiments indicated that there is no discernible reproductive isolation between them.

View Article: PubMed Central - PubMed

Affiliation: Division of EcoScience, Ewha Womans University 52, Ewhayeodae-gil, Seodaemun-gu, Seoul, Korea.

ABSTRACT
River connections via artificial canals will bring about secondary contacts between previously isolated fish species. Here, we present a genetic consequence of such a secondary contact between Cobitis fish species, C. lutheri in the Dongjin River, and C. tetralineata in the Seomjin River in Korea. The construction of water canals about 80 years ago has unidirectionally introduced C. tetralineata into the native habitat of C. lutheri, and then these species have hybridized in the main stream section of the Dongjin River. According to the divergence population genetic analyses of DNA sequence data, the two species diverged about 3.3 million years ago, which is interestingly coincident with the unprecedented paleoceanographic change that caused isolations of the paleo-river systems in northeast Asia due to sea-level changes around the late Pliocene. Multilocus genotypic data of nine microsatellites and three nuclear loci revealed an extensively admixed structure in the hybrid zone with a high proportion of various post-F1 hybrids. Surprisingly, pure native C. lutheri was absent in the hybrid zone in contrast to the 7% of pure C. tetralineata. Such a biased proportion must have resulted from the dominant influence of continually introducing C. tetralineata on the native C. lutheri which has no supply of natives from other tributaries to the hybrid zone due to numerous low-head dams. In addition, mating experiments indicated that there is no discernible reproductive isolation between them. All the results suggest that the gene pool of native C. lutheri is being rapidly replaced by that of continually introducing C. tetralineata through a hybrid swarm for the last 80 years, which will ultimately lead to the genomic extinction of natives in this hybrid zone.

No MeSH data available.