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Tracing the trans-pacific evolutionary history of a domesticated Seaweed (Gracilaria chilensis) with archaeological and genetic data.

Guillemin ML, Valero M, Faugeron S, Nelson W, Destombe C - PLoS ONE (2014)

Bottom Line: The history of a domesticated marine macroalga is studied using archaeological, phylogeographic and population genetic tools.Combining archaeological observations with phylogeographic data provided evidence that exchanges between New Zealand and Chile have occurred at least before the Holocene, likely at the end of the Last Glacial Maximum (LGM) and we suggest that migration probably occurred via rafting.Furthermore, the remarkably low microsatellite diversity found in the Chilean populations compared to those in New Zealand is consistent with a recent genetic bottleneck as a result of over-exploitation of natural populations and/or the process of domestication.

View Article: PubMed Central - PubMed

Affiliation: Instituto de Ciencias Ambientales y Evolutivas, Facultad de Ciencias, Universidad Austral de Chile, Casilla 567, Valdivia, Chile; CNRS, Sorbonne Universités, UPMC University Paris VI, UMI 3614, Evolutionary Biology and Ecology of Algae, Station Biologique de Roscoff, CS 90074, Place G. Tessier, 296888 Roscoff, France.

ABSTRACT
The history of a domesticated marine macroalga is studied using archaeological, phylogeographic and population genetic tools. Phylogeographic and population genetic analyses demonstrated that the cultivated red alga Gracilaria chilensis colonised the Chilean coast from New Zealand. Combining archaeological observations with phylogeographic data provided evidence that exchanges between New Zealand and Chile have occurred at least before the Holocene, likely at the end of the Last Glacial Maximum (LGM) and we suggest that migration probably occurred via rafting. Furthermore, the remarkably low microsatellite diversity found in the Chilean populations compared to those in New Zealand is consistent with a recent genetic bottleneck as a result of over-exploitation of natural populations and/or the process of domestication. Therefore, the aquaculture of this seaweed, based essentially on clonal propagation, is occurring from genetically depressed populations and may be driving the species to an extinction vortex in Chile.

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Related in: MedlinePlus

Genetic population structure of New Zealand and Chilean Gracilaria populations.(A) based on Bayesian analysis with STRUCTURE software [37], proportions of individual multilocus genotypes were assigned to each of the 5 virtual genetic clusters indicated by the different colours; (B) based on graph analysis with POPULATION GRAPH software [40], differences in node size reflect differences in within population variability whereas edge lengths represent the genetic variation between pairs of samples, there were significantly more edges within New Zealand and Chilean groups than between the two groups (P<0.0001). Node colour corresponds to the 5 clusters as determined by STRUCTURE. For both analyses: N = 7 New Zealand populations, 11 Chilean populations, 567 individuals, 5 codominant loci. Population codes are provided in Table S1.
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pone-0114039-g002: Genetic population structure of New Zealand and Chilean Gracilaria populations.(A) based on Bayesian analysis with STRUCTURE software [37], proportions of individual multilocus genotypes were assigned to each of the 5 virtual genetic clusters indicated by the different colours; (B) based on graph analysis with POPULATION GRAPH software [40], differences in node size reflect differences in within population variability whereas edge lengths represent the genetic variation between pairs of samples, there were significantly more edges within New Zealand and Chilean groups than between the two groups (P<0.0001). Node colour corresponds to the 5 clusters as determined by STRUCTURE. For both analyses: N = 7 New Zealand populations, 11 Chilean populations, 567 individuals, 5 codominant loci. Population codes are provided in Table S1.

Mentions: We found strong evidence for genetic divergence between New Zealand and Chilean populations supported by both model based clustering and graph theory analyses of microsatellite data (Figure 2A and 2B). First, there was a remarkable lack of admixture among populations (Figure 2A). All individuals within a given population were assigned to the same cluster, except for the NZ-PGB population in New Zealand. Second, the topology of the network has 42 edges with two visually identifiable sub-graphs corresponding to the different sides of the South Pacific Ocean (Figure 2B). The two connections between CH-LEN (Chile) and NZ-CHT and NZ-MOU (New Zealand) form the only link between the two continents revealing significant genetic differentiation between New Zealand and Chile (Figure 2B; P<0.0001). Only the POPULATION GRAPH resulting from the exclusion of CH-LEN population located in the Araucanian region reveals two distinct disconnected sub-graphs suggesting that this region could be the unique source of transpacific connectivity. In addition, the Araucanian region hosts the three most genetically diverse populations in Chile for both allele and haplotype richness (i.e. CH-DIC, CH-LEN and CH-TUB; Table S1). In the west Pacific area, populations were highly genetically differentiated based on microsatellite data. Three clear clusters were defined separating the Chatham Islands population from New Zealand populations (Figure 1). Even if populations located in the eastern part of the Cook Strait (NZ-PIW, NZ-SCB and NZ-MOU) were grouped in the same cluster, no clear geographic pattern was observed in New Zealand (Figure 1). In contrast, ITS2 supports a strong Western and Eastern separation of New Zealand populations with highly divergent ribotypes restricted to the three westernmost populations (NZ-WIN, NZ-PGB and NZ-MOU, Figure 1). In Chile, two well-differentiated groups of populations were identified based on microsatellite data analyses but these did not correspond to a geographic arrangement of sampling sites (Figure 2A and 2B). This structure was not seen with the ITS2 owing to the presence of the ribotype r1 at high frequency in all Chilean populations (Figure 1).


Tracing the trans-pacific evolutionary history of a domesticated Seaweed (Gracilaria chilensis) with archaeological and genetic data.

Guillemin ML, Valero M, Faugeron S, Nelson W, Destombe C - PLoS ONE (2014)

Genetic population structure of New Zealand and Chilean Gracilaria populations.(A) based on Bayesian analysis with STRUCTURE software [37], proportions of individual multilocus genotypes were assigned to each of the 5 virtual genetic clusters indicated by the different colours; (B) based on graph analysis with POPULATION GRAPH software [40], differences in node size reflect differences in within population variability whereas edge lengths represent the genetic variation between pairs of samples, there were significantly more edges within New Zealand and Chilean groups than between the two groups (P<0.0001). Node colour corresponds to the 5 clusters as determined by STRUCTURE. For both analyses: N = 7 New Zealand populations, 11 Chilean populations, 567 individuals, 5 codominant loci. Population codes are provided in Table S1.
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4263469&req=5

pone-0114039-g002: Genetic population structure of New Zealand and Chilean Gracilaria populations.(A) based on Bayesian analysis with STRUCTURE software [37], proportions of individual multilocus genotypes were assigned to each of the 5 virtual genetic clusters indicated by the different colours; (B) based on graph analysis with POPULATION GRAPH software [40], differences in node size reflect differences in within population variability whereas edge lengths represent the genetic variation between pairs of samples, there were significantly more edges within New Zealand and Chilean groups than between the two groups (P<0.0001). Node colour corresponds to the 5 clusters as determined by STRUCTURE. For both analyses: N = 7 New Zealand populations, 11 Chilean populations, 567 individuals, 5 codominant loci. Population codes are provided in Table S1.
Mentions: We found strong evidence for genetic divergence between New Zealand and Chilean populations supported by both model based clustering and graph theory analyses of microsatellite data (Figure 2A and 2B). First, there was a remarkable lack of admixture among populations (Figure 2A). All individuals within a given population were assigned to the same cluster, except for the NZ-PGB population in New Zealand. Second, the topology of the network has 42 edges with two visually identifiable sub-graphs corresponding to the different sides of the South Pacific Ocean (Figure 2B). The two connections between CH-LEN (Chile) and NZ-CHT and NZ-MOU (New Zealand) form the only link between the two continents revealing significant genetic differentiation between New Zealand and Chile (Figure 2B; P<0.0001). Only the POPULATION GRAPH resulting from the exclusion of CH-LEN population located in the Araucanian region reveals two distinct disconnected sub-graphs suggesting that this region could be the unique source of transpacific connectivity. In addition, the Araucanian region hosts the three most genetically diverse populations in Chile for both allele and haplotype richness (i.e. CH-DIC, CH-LEN and CH-TUB; Table S1). In the west Pacific area, populations were highly genetically differentiated based on microsatellite data. Three clear clusters were defined separating the Chatham Islands population from New Zealand populations (Figure 1). Even if populations located in the eastern part of the Cook Strait (NZ-PIW, NZ-SCB and NZ-MOU) were grouped in the same cluster, no clear geographic pattern was observed in New Zealand (Figure 1). In contrast, ITS2 supports a strong Western and Eastern separation of New Zealand populations with highly divergent ribotypes restricted to the three westernmost populations (NZ-WIN, NZ-PGB and NZ-MOU, Figure 1). In Chile, two well-differentiated groups of populations were identified based on microsatellite data analyses but these did not correspond to a geographic arrangement of sampling sites (Figure 2A and 2B). This structure was not seen with the ITS2 owing to the presence of the ribotype r1 at high frequency in all Chilean populations (Figure 1).

Bottom Line: The history of a domesticated marine macroalga is studied using archaeological, phylogeographic and population genetic tools.Combining archaeological observations with phylogeographic data provided evidence that exchanges between New Zealand and Chile have occurred at least before the Holocene, likely at the end of the Last Glacial Maximum (LGM) and we suggest that migration probably occurred via rafting.Furthermore, the remarkably low microsatellite diversity found in the Chilean populations compared to those in New Zealand is consistent with a recent genetic bottleneck as a result of over-exploitation of natural populations and/or the process of domestication.

View Article: PubMed Central - PubMed

Affiliation: Instituto de Ciencias Ambientales y Evolutivas, Facultad de Ciencias, Universidad Austral de Chile, Casilla 567, Valdivia, Chile; CNRS, Sorbonne Universités, UPMC University Paris VI, UMI 3614, Evolutionary Biology and Ecology of Algae, Station Biologique de Roscoff, CS 90074, Place G. Tessier, 296888 Roscoff, France.

ABSTRACT
The history of a domesticated marine macroalga is studied using archaeological, phylogeographic and population genetic tools. Phylogeographic and population genetic analyses demonstrated that the cultivated red alga Gracilaria chilensis colonised the Chilean coast from New Zealand. Combining archaeological observations with phylogeographic data provided evidence that exchanges between New Zealand and Chile have occurred at least before the Holocene, likely at the end of the Last Glacial Maximum (LGM) and we suggest that migration probably occurred via rafting. Furthermore, the remarkably low microsatellite diversity found in the Chilean populations compared to those in New Zealand is consistent with a recent genetic bottleneck as a result of over-exploitation of natural populations and/or the process of domestication. Therefore, the aquaculture of this seaweed, based essentially on clonal propagation, is occurring from genetically depressed populations and may be driving the species to an extinction vortex in Chile.

Show MeSH
Related in: MedlinePlus