Limits...
Conflicting evolutionary patterns due to mitochondrial introgression and multilocus phylogeography of the Patagonian freshwater crab Aegla neuquensis.

Barber BR, Xu J, Pérez-Losada M, Jara CG, Crandall KA - PLoS ONE (2012)

Bottom Line: However, the mitochondrial locus provided greater resolution on more recent evolutionary events.Our study, therefore, demonstrates the need to include both nuclear and mitochondrial loci for a more complete understanding of evolutionary histories and associated phylogeographic events.Our results suggest that gene flow between these systems, before and after fragmentation was through periodic paleolakes that formed in the headwaters region.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Brigham Young University, Provo, Utah, United States of America. brbarber76@gmail.com

ABSTRACT

Background: Multiple loci and population genetic methods were employed to study the phylogeographic history of the Patagonian freshwater crab Aegla neuquensis (Aeglidae: Decopoda). This taxon occurs in two large river systems in the Patagonian Steppe, from the foothills of the Andes Mountains east to the Atlantic Ocean.

Methodology/principal findings: A nuclear phylogeny and multilocus nested clade phylogeographic analysis detected a fragmentation event between the Negro and Chico-Chubut river systems. This event occurred approximately 137 thousand years ago. An isolation-with-migration analysis and maximum-likelihood estimates of gene flow showed asymmetrical exchange of genetic material between these two river systems exclusively in their headwaters. We used information theory to determine the best-fit demographic history between these two river systems under an isolation-with-migration model. The best-fit model suggests that the Negro and the ancestral populations have the same effective population sizes; whereas the Chico-Chubut population is smaller and shows that gene flow from the Chico-Chubut into the Negro is four times higher than in the reverse direction. Much of the Chico-Chubut system appears to have only been recently colonized while the Negro populations appear to have been in place for most of the evolutionary history of this taxon.

Conclusions/significance: Due to mitochondrial introgression, three nuclear loci provided different phylogeographic resolution than the three mitochondrial genes for an ancient fragmentation event observed in the nuclear phylogeny. However, the mitochondrial locus provided greater resolution on more recent evolutionary events. Our study, therefore, demonstrates the need to include both nuclear and mitochondrial loci for a more complete understanding of evolutionary histories and associated phylogeographic events. Our results suggest that gene flow between these systems, before and after fragmentation was through periodic paleolakes that formed in the headwaters region. Fragmentation between the Negro and Chico-Chubut systems was driven by the disappearance of these paleolakes during the Patagonian Glaciation.

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Gene flow estimates for mtDNA and a combined nDNA analysis using MIGRATE [71].A thick arrow indicates gene flow that is at least two-times greater in one direction than the opposite direction. Color codes indicate the six major rivers.
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pone-0037105-g010: Gene flow estimates for mtDNA and a combined nDNA analysis using MIGRATE [71].A thick arrow indicates gene flow that is at least two-times greater in one direction than the opposite direction. Color codes indicate the six major rivers.

Mentions: Asymmetrical gene flow was observed in both mtDNA and nDNA with a greater magnitude of downstream flow detected within the Neuquen and Negro river system (Fig. 10). Similar patterns between mtDNA and nDNA suggests that there is no sex biased gene flow. Both mtDNA and nDNA suggest that the majority of populations in the upper reaches of the Limay River are exchanging genes. In the Chubut and Chico rivers, only mtDNA possessed sufficient variation to provide reliable estimates. In the Chubut system mitochondrial gene flow is occurring both upstream and downstream from the Los Altares population. Conversely, in the Chico River all gene flow is following an upstream pattern with no detectable flow occurring downstream. Both the Pichileufu and Comallo populations in the Limay River have exchanged nDNA with the Las Bayas population of the Chico River. In contrast, only the Pichileufu population has experienced mtDNA gene flow from Last Bayas and this gene flow was asymmetrical with Pichileufu receiving immigrants from Las Bayas.


Conflicting evolutionary patterns due to mitochondrial introgression and multilocus phylogeography of the Patagonian freshwater crab Aegla neuquensis.

Barber BR, Xu J, Pérez-Losada M, Jara CG, Crandall KA - PLoS ONE (2012)

Gene flow estimates for mtDNA and a combined nDNA analysis using MIGRATE [71].A thick arrow indicates gene flow that is at least two-times greater in one direction than the opposite direction. Color codes indicate the six major rivers.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3369872&req=5

pone-0037105-g010: Gene flow estimates for mtDNA and a combined nDNA analysis using MIGRATE [71].A thick arrow indicates gene flow that is at least two-times greater in one direction than the opposite direction. Color codes indicate the six major rivers.
Mentions: Asymmetrical gene flow was observed in both mtDNA and nDNA with a greater magnitude of downstream flow detected within the Neuquen and Negro river system (Fig. 10). Similar patterns between mtDNA and nDNA suggests that there is no sex biased gene flow. Both mtDNA and nDNA suggest that the majority of populations in the upper reaches of the Limay River are exchanging genes. In the Chubut and Chico rivers, only mtDNA possessed sufficient variation to provide reliable estimates. In the Chubut system mitochondrial gene flow is occurring both upstream and downstream from the Los Altares population. Conversely, in the Chico River all gene flow is following an upstream pattern with no detectable flow occurring downstream. Both the Pichileufu and Comallo populations in the Limay River have exchanged nDNA with the Las Bayas population of the Chico River. In contrast, only the Pichileufu population has experienced mtDNA gene flow from Last Bayas and this gene flow was asymmetrical with Pichileufu receiving immigrants from Las Bayas.

Bottom Line: However, the mitochondrial locus provided greater resolution on more recent evolutionary events.Our study, therefore, demonstrates the need to include both nuclear and mitochondrial loci for a more complete understanding of evolutionary histories and associated phylogeographic events.Our results suggest that gene flow between these systems, before and after fragmentation was through periodic paleolakes that formed in the headwaters region.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Brigham Young University, Provo, Utah, United States of America. brbarber76@gmail.com

ABSTRACT

Background: Multiple loci and population genetic methods were employed to study the phylogeographic history of the Patagonian freshwater crab Aegla neuquensis (Aeglidae: Decopoda). This taxon occurs in two large river systems in the Patagonian Steppe, from the foothills of the Andes Mountains east to the Atlantic Ocean.

Methodology/principal findings: A nuclear phylogeny and multilocus nested clade phylogeographic analysis detected a fragmentation event between the Negro and Chico-Chubut river systems. This event occurred approximately 137 thousand years ago. An isolation-with-migration analysis and maximum-likelihood estimates of gene flow showed asymmetrical exchange of genetic material between these two river systems exclusively in their headwaters. We used information theory to determine the best-fit demographic history between these two river systems under an isolation-with-migration model. The best-fit model suggests that the Negro and the ancestral populations have the same effective population sizes; whereas the Chico-Chubut population is smaller and shows that gene flow from the Chico-Chubut into the Negro is four times higher than in the reverse direction. Much of the Chico-Chubut system appears to have only been recently colonized while the Negro populations appear to have been in place for most of the evolutionary history of this taxon.

Conclusions/significance: Due to mitochondrial introgression, three nuclear loci provided different phylogeographic resolution than the three mitochondrial genes for an ancient fragmentation event observed in the nuclear phylogeny. However, the mitochondrial locus provided greater resolution on more recent evolutionary events. Our study, therefore, demonstrates the need to include both nuclear and mitochondrial loci for a more complete understanding of evolutionary histories and associated phylogeographic events. Our results suggest that gene flow between these systems, before and after fragmentation was through periodic paleolakes that formed in the headwaters region. Fragmentation between the Negro and Chico-Chubut systems was driven by the disappearance of these paleolakes during the Patagonian Glaciation.

Show MeSH
Related in: MedlinePlus