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Anthropogenic hybridization between endangered migratory and commercially harvested stationary whitefish taxa (Coregonus spp.).

Dierking J, Phelps L, Præbel K, Ramm G, Prigge E, Borcherding J, Brunke M, Eizaguirre C - Evol Appl (2014)

Bottom Line: We focused on three naturally reproductively isolated whitefish taxa in Germany: the endangered, anadromous North Sea houting (NSH) and Baltic houting (BH), which were reintroduced after local extinction, and the commercially stocked European whitefish (EW).The BH distribution range showed higher heterogeneity and stronger admixture than the NSH range.Erroneous stocking with non-native genotypes best explained these patterns, which pose challenges for the conservation of the endangered NSH and BH.

View Article: PubMed Central - PubMed

Affiliation: Research Division Marine Ecology, Research Unit Evolutionary Ecology of Marine Fishes, GEOMAR Helmholtz Centre for Ocean Research Kiel, Germany.

ABSTRACT
Natural hybridization plays a key role in the process of speciation. However, anthropogenic (human induced) hybridization of historically isolated taxa raises conservation issues. Due to weak barriers to gene flow and the presence of endangered taxa, the whitefish species complex is an excellent study system to investigate the consequences of hybridization in conservation. We focused on three naturally reproductively isolated whitefish taxa in Germany: the endangered, anadromous North Sea houting (NSH) and Baltic houting (BH), which were reintroduced after local extinction, and the commercially stocked European whitefish (EW). To evaluate the genetic integrity of each taxon, source and reintroduced populations of NSH and BH, and EW populations were characterized based on two mitochondrial and 17 microsatellite loci. Additionally, we investigated gill raker counts as an adaptive phenotypic trait. Even though clear genetic and phenotypic differentiation confirmed the houtings as separate evolutionarily significant units, admixture analyses revealed an extensive hybrid zone. Hybridizations were introgressive, positively correlated with genetic diversity, and were reflected in the gill raker counts. The BH distribution range showed higher heterogeneity and stronger admixture than the NSH range. Erroneous stocking with non-native genotypes best explained these patterns, which pose challenges for the conservation of the endangered NSH and BH.

No MeSH data available.


Related in: MedlinePlus

Genetic differentiation (Fst – values based on microsatellites) of source populations from reintroduced populations across the historic North Sea houting (NSH) (left of dotted line) and Baltic houting (BH) (right of dotted line) ranges. Putative source of NSH reintroductions: NSH_VID (blue); putative source of BH reintroductions: BH_PEE (red); European whitefish (EW) from EW_BOR (blue) is added as potential additional source.
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fig03: Genetic differentiation (Fst – values based on microsatellites) of source populations from reintroduced populations across the historic North Sea houting (NSH) (left of dotted line) and Baltic houting (BH) (right of dotted line) ranges. Putative source of NSH reintroductions: NSH_VID (blue); putative source of BH reintroductions: BH_PEE (red); European whitefish (EW) from EW_BOR (blue) is added as potential additional source.

Mentions: While some loci showed deviations from HWE for individual populations, no general patterns were present and all loci were included in the analyses. The genetic integrity of the indigenous source populations detected with mtDNA also held true when investigating nuclear loci (Table3). Specifically, the sources of NSH and BH and EW populations were strongly and significantly differentiated from each other (NSH_VID versus BH PEE, Fst = 0.15, P < 0.001; Fsts > 0.10 and P < 0.001 for all pairwise comparisons of NSH_VID and BH_PEE versus EW populations) (Table3). Contemporary gene flow among populations within distribution ranges proved to be very low with all pairwise population tests being significant except NSH_ELB versus NSH_RHI (Fst = 0.01, P = 0.30), BH_SCH versus BH_LAC (Fst = 0.01, P = 0.06) and BH_TRA versus BH_PEE (Fst = 0.01, P = 0.054). Interestingly, the latter comparison is the only one showing no significant differentiation from the source population within a given distribution range, and all reintroduced populations showed intermediate differentiation between the putative source and other source populations (Fig.3). The differences between the historic distribution ranges and among populations within ranges both explained significant and approximately equal proportions of molecular variance (amova, Table S5). The general pattern of population clustering within the distribution ranges of NSH and BH was confirmed by the neighbor-joining tree (Fig.4). Interestingly, both Fst values and the neighbor-joining tree showed that the population from the Kiel Canal, contrary to expectation, clearly clustered with EW and not within the BH range.


Anthropogenic hybridization between endangered migratory and commercially harvested stationary whitefish taxa (Coregonus spp.).

Dierking J, Phelps L, Præbel K, Ramm G, Prigge E, Borcherding J, Brunke M, Eizaguirre C - Evol Appl (2014)

Genetic differentiation (Fst – values based on microsatellites) of source populations from reintroduced populations across the historic North Sea houting (NSH) (left of dotted line) and Baltic houting (BH) (right of dotted line) ranges. Putative source of NSH reintroductions: NSH_VID (blue); putative source of BH reintroductions: BH_PEE (red); European whitefish (EW) from EW_BOR (blue) is added as potential additional source.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4231596&req=5

fig03: Genetic differentiation (Fst – values based on microsatellites) of source populations from reintroduced populations across the historic North Sea houting (NSH) (left of dotted line) and Baltic houting (BH) (right of dotted line) ranges. Putative source of NSH reintroductions: NSH_VID (blue); putative source of BH reintroductions: BH_PEE (red); European whitefish (EW) from EW_BOR (blue) is added as potential additional source.
Mentions: While some loci showed deviations from HWE for individual populations, no general patterns were present and all loci were included in the analyses. The genetic integrity of the indigenous source populations detected with mtDNA also held true when investigating nuclear loci (Table3). Specifically, the sources of NSH and BH and EW populations were strongly and significantly differentiated from each other (NSH_VID versus BH PEE, Fst = 0.15, P < 0.001; Fsts > 0.10 and P < 0.001 for all pairwise comparisons of NSH_VID and BH_PEE versus EW populations) (Table3). Contemporary gene flow among populations within distribution ranges proved to be very low with all pairwise population tests being significant except NSH_ELB versus NSH_RHI (Fst = 0.01, P = 0.30), BH_SCH versus BH_LAC (Fst = 0.01, P = 0.06) and BH_TRA versus BH_PEE (Fst = 0.01, P = 0.054). Interestingly, the latter comparison is the only one showing no significant differentiation from the source population within a given distribution range, and all reintroduced populations showed intermediate differentiation between the putative source and other source populations (Fig.3). The differences between the historic distribution ranges and among populations within ranges both explained significant and approximately equal proportions of molecular variance (amova, Table S5). The general pattern of population clustering within the distribution ranges of NSH and BH was confirmed by the neighbor-joining tree (Fig.4). Interestingly, both Fst values and the neighbor-joining tree showed that the population from the Kiel Canal, contrary to expectation, clearly clustered with EW and not within the BH range.

Bottom Line: We focused on three naturally reproductively isolated whitefish taxa in Germany: the endangered, anadromous North Sea houting (NSH) and Baltic houting (BH), which were reintroduced after local extinction, and the commercially stocked European whitefish (EW).The BH distribution range showed higher heterogeneity and stronger admixture than the NSH range.Erroneous stocking with non-native genotypes best explained these patterns, which pose challenges for the conservation of the endangered NSH and BH.

View Article: PubMed Central - PubMed

Affiliation: Research Division Marine Ecology, Research Unit Evolutionary Ecology of Marine Fishes, GEOMAR Helmholtz Centre for Ocean Research Kiel, Germany.

ABSTRACT
Natural hybridization plays a key role in the process of speciation. However, anthropogenic (human induced) hybridization of historically isolated taxa raises conservation issues. Due to weak barriers to gene flow and the presence of endangered taxa, the whitefish species complex is an excellent study system to investigate the consequences of hybridization in conservation. We focused on three naturally reproductively isolated whitefish taxa in Germany: the endangered, anadromous North Sea houting (NSH) and Baltic houting (BH), which were reintroduced after local extinction, and the commercially stocked European whitefish (EW). To evaluate the genetic integrity of each taxon, source and reintroduced populations of NSH and BH, and EW populations were characterized based on two mitochondrial and 17 microsatellite loci. Additionally, we investigated gill raker counts as an adaptive phenotypic trait. Even though clear genetic and phenotypic differentiation confirmed the houtings as separate evolutionarily significant units, admixture analyses revealed an extensive hybrid zone. Hybridizations were introgressive, positively correlated with genetic diversity, and were reflected in the gill raker counts. The BH distribution range showed higher heterogeneity and stronger admixture than the NSH range. Erroneous stocking with non-native genotypes best explained these patterns, which pose challenges for the conservation of the endangered NSH and BH.

No MeSH data available.


Related in: MedlinePlus