Mito-nuclear discord in six congeneric lineages of Holarctic ducks (genus Anas).
Many species have Holarctic distributions that extend across Europe, Asia and North America. Most genetics research on these species has examined only mitochondrial (mt) DNA, which has revealed wide variance in divergence between Old World (OW) and New World (NW) populations, ranging from shallow, unstructured genealogies to deeply divergent lineages. In this study, we sequenced 20 nuclear introns to test for concordant patterns of OW-NW differentiation between mtDNA and nuclear (nu) DNA for six lineages of Holarctic ducks (genus Anas). Genetic differentiation for both marker types varied widely among these lineages (idiosyncratic population histories), but mtDNA and nuDNA divergence within lineages was not significantly correlated. Moreover, compared with the association between mtDNA and nuDNA divergence observed among different species, OW-NW nuDNA differentiation was generally lower than mtDNA divergence, at least for lineages with deeply divergent mtDNA. Furthermore, coalescent estimates indicated significantly higher rates of gene flow for nuDNA than mtDNA for four of the six lineages. Thus, Holarctic ducks show prominent mito-nuclear discord between OW and NW populations, and we reject differences in sorting rates as the sole cause of the within-species discord. Male-mediated intercontinental gene flow is likely a leading contributor to this discord, although selection could also cause increased mtDNA divergence relative to weak nuDNA differentiation. The population genetics of these ducks contribute to growing evidence that mtDNA can be an unreliable indicator of stage of speciation and that more holistic approaches are needed for species delimitation.
Department of Biological Sciences, Wright State University, 3640 Colonel Glenn Hwy, Dayton, OH, 45435, USA.
Jeffrey L
JL
Peters
Kevin
K
Winker
Kendra C
KC
Millam
Philip
P
Lavretsky
Irina
I
Kulikova
Robert E
RE
Wilson
Yuri N
YN
Zhuravlev
Kevin G
KG
McCracken
D000818:Animals; D002467:Cell Nucleus / Q000235:genetics; D004272:DNA, Mitochondrial / Q000235:genetics; D004372:Ducks / Q000145:classification* / Q000235:genetics; D051456:Gene Flow; D049810:Genetic Speciation; D005828:Genetics, Population; D006239:Haplotypes; D007438:Introns; D008969:Molecular Sequence Data; D010641:Phenotype; D017422:Sequence Analysis, DNA
D004272:DNA, Mitochondrial
Anatidae; comparative phylogeography; dabbling ducks; genetic drift; selection; sex-biased gene flow