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BMC Genetics 2011
Interpopulation hybridization results in widespread viability selection across the genome in Tigriopus californicusAbstract: We generated a linkage map which included 45 newly elucidated SNPs and 8 population-diagnostic microsatellites used in previous studies. The map, the first available for the Copepoda, was estimated to cover 75% of the genome and included markers on all 12 T. californicus chromosomes. We observed little segregation distortion in newly hatched F2 hybrid larvae (fewer than 10% of markers at p < 0.05), but strikingly higher distortion in F2 hybrid adult males (45% of markers at p < 0.05). Hence, segregation distortion was primarily caused by selection against particular genetic combinations which acted between hatching and maturity. Distorted markers were not distributed randomly across the genome but clustered on particular chromosomes. In contrast to other studies in this species we found little evidence for cytonuclear coadaptation. Instead, different linkage groups exhibited markedly different patterns of distortion, which appear to have been influenced by nuclear-nuclear epistatic interactions and may also reflect genetic load carried within the parental lines.Adult male F2 hybrids between two populations of T. californius exhibit dramatic segregation distortion across the genome. Distorted loci are clustered within specific linkage groups, and the direction of distortion differs between chromosomes. This segregation distortion is due to selection acting between hatching and adulthood.One way in which the integrity of species can be maintained is by intrinsic postzygotic barriers which reduce the fitness of hybrid offspring. Understanding how genetic interactions within interpopulation hybrids influence fitness is hence an important step towards understanding how new species arise. When gene flow between populations is restricted, they can diverge as a result of selection and drift. One outcome of this divergence may be the accumulation of 'Dobzhansky-Muller incompatibilities', mutations which only become deleterious when placed on a novel genetic background in hyb
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