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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Map showing the sampling locations for Aegla neuquensis.The gray area indicates the ice sheet during the last glacial maximum (LGM: 23–24 ka). A picture of A. neuquensis is shown.
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pone-0037105-g001: Map showing the sampling locations for Aegla neuquensis.The gray area indicates the ice sheet during the last glacial maximum (LGM: 23–24 ka). A picture of A. neuquensis is shown.

Mentions: While NCPA found multiple significant inferences (Table 3), only three were detected across two or more loci (Table 4). Only these three will be considered for further discussion. Fragmentation (either past-fragmentation [PF] or allopatric-fragmentation [AF]) between the Limay and Chubut rivers was inferred in all four loci. As predicted this fragmentation event occurred between the headwaters of the Limay and Chubut rivers near the base of the Andes (Fig. 1). Restricted gene flow (RGF) was detected in the Chubut (three loci: ANT Intron, EF1 Exon, EF1 Intron) as well as in the Neuquen/Negro River (two loci: mtDNA and ANT Intron) systems.


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)

Map showing the sampling locations for Aegla neuquensis.The gray area indicates the ice sheet during the last glacial maximum (LGM: 23–24 ka). A picture of A. neuquensis is shown.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0037105-g001: Map showing the sampling locations for Aegla neuquensis.The gray area indicates the ice sheet during the last glacial maximum (LGM: 23–24 ka). A picture of A. neuquensis is shown.
Mentions: While NCPA found multiple significant inferences (Table 3), only three were detected across two or more loci (Table 4). Only these three will be considered for further discussion. Fragmentation (either past-fragmentation [PF] or allopatric-fragmentation [AF]) between the Limay and Chubut rivers was inferred in all four loci. As predicted this fragmentation event occurred between the headwaters of the Limay and Chubut rivers near the base of the Andes (Fig. 1). Restricted gene flow (RGF) was detected in the Chubut (three loci: ANT Intron, EF1 Exon, EF1 Intron) as well as in the Neuquen/Negro River (two loci: mtDNA and ANT Intron) systems.

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