Low mitochondrial variability in birds may indicate Hill-Robertson effects on the W chromosome.
Interference among loci subject to selection (the Hill-Robertson effect) may considerably reduce levels of adaptation and variability in genomic regions that lack recombination. Y- or W chromosomes are particularly vulnerable to such effects, since they represent large, non-recombining blocks of genetic material. In birds, the W chromosome and mitochondrial genomes are both maternally transmitted, and hence fail to recombine with each other, whereas in mammals the Y chromosome is paternally transmitted. We show here that mitochondrial DNA sequence diversity is reduced in non-ratite birds compared with mammals. After considering possible confounding factors, such as differences in generation times, mutation rates and demography, we conclude that Hill-Robertson effects associated with the W chromosome provide the most likely explanation for this difference.
Berlin
S
S
Department of Genetics and Genomics, Roslin Institute (Edinburgh), Midlothian, UK. sofia.berlin@ebc.uu.se
Tomaras
D
D
Charlesworth
B
B
D000818:Animals; D001717:Birds / Q000235:genetics*; D002874:Chromosome Mapping; D004272:DNA, Mitochondrial / Q000235:genetics; D005260:Female; D014644:Genetic Variation; D005828:Genetics, Population; D054629:Genome, Mitochondrial; D008297:Male; D008928:Mitochondria / Q000378:metabolism*; D008957:Models, Genetic; D015233:Models, Statistical; D011995:Recombination, Genetic; D017422:Sequence Analysis, DNA
D004272:DNA, Mitochondrial