Conflicting Evolutionary Patterns Due to Mitochondrial Introgression and Multilocus Phylogeography of the Patagonian Freshwater Crab Aegla neuquensis

Abstract

BackgroundMultiple 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 FindingsA 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/SignificanceDue 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.

Echoes of a distant time: effects of historical processes on contemporary genetic patterns in Galaxias platei in Patagonia

“…, ; Barber et al . ). Paleolakes acted as glacial refugia allowing the in situ survival of cold‐adapted aquatic species during the Quaternary glacial cycles and their subsequent expansion into new areas through colonization and recolonization processes (Zemlak et al .…”

“…Historical and contemporary patterns San Pedro system. Paleolakes were not unusual in Patagonia (Caldenius 1932;Clapperton 1994;Clapperton et al 1995;Bell 2008;Hein et al 2010); while their extension ranged from a few tens to hundreds of kilometres (Bell 2008), their biological significance and potential role in the distribution of freshwater species has only recently begun to be disentangled (Ruzzante et al 2006(Ruzzante et al , 2008Barber et al 2012). Paleolakes acted as glacial refugia allowing the in situ survival of cold-adapted aquatic species during the Quaternary glacial cycles and their subsequent expansion into new areas through colonization and recolonization processes (Zemlak et al 2008;Xu et al 2009).…”

Population genetic structure of the freshwater anomuran Aegla uruguayana Schmitt, 1942 (Decapoda, Aeglidae) in the central region of Argentina

“…In freshwater decapods, population genetic evidence studies suggest different patterns that indicate structural levels according to distance or population separa tion in time or space, or variations according to habitat area, habitat age, and the immigration potential of the locality (Fuller & Lester, 1980;Daniels et ah, 1999;Daniels, 2003;Schubart & Huber, 2006;Shih et al, 2006;Xu et al, 2009;Klinbunga et al, 2010;Barber et al, 2011Barber et al, , 2012.…”

“…Aeglids population variability by molecular or genetic evidence is scarce (D'Amato & Corach, 1997a, b;Santos et al" 2009;Xu et a l, 2009;Barber et al, 2011Barber et al, , 2012. Here, we applied the Inter Simple Sequence Repeat (ISSR) marker, which is a relatively recent technique (Bomet & Branchard, 2001), to evaluate variation in microsatellite regions.…”

Failed species, innominate forms, and the vain search for species limits: cryptic diversity in dusky salamanders (Desmognathus) of eastern Tennessee

“…Rapidly evolving mtDNA sequences may be especially subject to homoplasy (Ballard and Rand 2005;Rubinoff and Holland 2005;Zink and Barrowclough 2008;Fisher-Reid and Wiens 2011) and subject to transfer between lineages via "cytoplasmic capture" (Avise 2004;Chan and Levin 2005). Mitochondrial and nuclear loci can reveal different patterns of exchange via maternal inheritance, gender-biased dispersal, and frequency-dependent mate choice (Irwin 2002;Chan and Levin 2005;Richmond and Jockusch 2007;Barber et al 2012). Several examples of discordance between mitochondrial and species phylogenies have thus been documented (e.g., Linnen and Farrell 2007;Wiens et al 2010;Fisher-Reid and Wiens 2011).…”