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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.


Bar plot of the posterior probabilities of hybrid classes for the individuals from the hybrid zone in the Dongjin River computed by NewHybrids. Numbers under the histogram are locality numbers shown in Table 1. P0, pure Cobitis lutheri; B0, backcrosses with pure C. lutheri; F1, F1 hybrid; F2, F2 hybrid; B1, backcrosses with pure C. tetralineata; P1, pure C. tetralineata. Asterisks on the bar plot indicate the mitochondrial Cyt b haplotype of C. tetralineata. P0, B0, and F1 individuals are absent in the hybrid zone.
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fig06: Bar plot of the posterior probabilities of hybrid classes for the individuals from the hybrid zone in the Dongjin River computed by NewHybrids. Numbers under the histogram are locality numbers shown in Table 1. P0, pure Cobitis lutheri; B0, backcrosses with pure C. lutheri; F1, F1 hybrid; F2, F2 hybrid; B1, backcrosses with pure C. tetralineata; P1, pure C. tetralineata. Asterisks on the bar plot indicate the mitochondrial Cyt b haplotype of C. tetralineata. P0, B0, and F1 individuals are absent in the hybrid zone.

Mentions: After confirming the intensive interspecific hybridization, we characterized the individuals of the Dongjin River by fitting them into the proposed six classes of hybrid after two generations of hybridization using NewHybrids. To minimize misidentification, we used a reliable threshold posterior probability of 0.50 for NewHybrids (Vähä and Primmer 2006; Winkler et al. 2011). The NewHybrids analysis showed that most of individuals from the hybrid zone could be classified as follows: 6 pure C. tetralineata (P1 in Fig. 6), 9 backcrossed individuals with C. tetralineata (B1) and 68 F2 descendants (F2), with high posterior probabilities. No individuals were identified as being pure C. lutheri (P0), backcrossed with C. lutheri (B0) or F1 hybrids (F1). The individuals categorized into P1 or B1 were highly corresponded with Cyt b gene of C. tetralineata, while F2 hybrids were relatively unbiased for the Cyt b (chi-square = 8.046, df = 2, P = 0.016, Fig. S2).


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)

Bar plot of the posterior probabilities of hybrid classes for the individuals from the hybrid zone in the Dongjin River computed by NewHybrids. Numbers under the histogram are locality numbers shown in Table 1. P0, pure Cobitis lutheri; B0, backcrosses with pure C. lutheri; F1, F1 hybrid; F2, F2 hybrid; B1, backcrosses with pure C. tetralineata; P1, pure C. tetralineata. Asterisks on the bar plot indicate the mitochondrial Cyt b haplotype of C. tetralineata. P0, B0, and F1 individuals are absent in the hybrid zone.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig06: Bar plot of the posterior probabilities of hybrid classes for the individuals from the hybrid zone in the Dongjin River computed by NewHybrids. Numbers under the histogram are locality numbers shown in Table 1. P0, pure Cobitis lutheri; B0, backcrosses with pure C. lutheri; F1, F1 hybrid; F2, F2 hybrid; B1, backcrosses with pure C. tetralineata; P1, pure C. tetralineata. Asterisks on the bar plot indicate the mitochondrial Cyt b haplotype of C. tetralineata. P0, B0, and F1 individuals are absent in the hybrid zone.
Mentions: After confirming the intensive interspecific hybridization, we characterized the individuals of the Dongjin River by fitting them into the proposed six classes of hybrid after two generations of hybridization using NewHybrids. To minimize misidentification, we used a reliable threshold posterior probability of 0.50 for NewHybrids (Vähä and Primmer 2006; Winkler et al. 2011). The NewHybrids analysis showed that most of individuals from the hybrid zone could be classified as follows: 6 pure C. tetralineata (P1 in Fig. 6), 9 backcrossed individuals with C. tetralineata (B1) and 68 F2 descendants (F2), with high posterior probabilities. No individuals were identified as being pure C. lutheri (P0), backcrossed with C. lutheri (B0) or F1 hybrids (F1). The individuals categorized into P1 or B1 were highly corresponded with Cyt b gene of C. tetralineata, while F2 hybrids were relatively unbiased for the Cyt b (chi-square = 8.046, df = 2, P = 0.016, Fig. S2).

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.