Dorsal skin color patterns among southern right whales (Eubalaena australis): Genetic basis and evolutionary significance

Distribution and inheritance of dorsal skin color markings among two popula tions of southern right whales (Eubalaena australis) suggest that two genes influence dorsal skin color. The grey-morph and partial-grey-morph phenoty pes (previously known as partial albino and grey-blaze, respectively) appea r to be controlled by an X-linked gene, whereas the white blaze appears con trolled by an autosomal gene (recessive phenotype), Calving intervals, calf size, and length of sighting history data suggest that partial-grey-morph, white-blaze, and black cows experience similar levels of reproductive succ ess. Grey-morph cows ((XXg)-X-g) are rare or absent in the two populations, but this was not unexpected given observed population frequencies of grey- morph males ((XY)-Y-g) and partial-grey-morph females ((XXg)-X-G). The prop ortion of partial-grey-morph calves produced by black cows ((XXG)-X-G) sugg ests that the reproductive success of grey-morph males was equal to that of black males, however, larger sample sizes are required to determine whethe r grey-morph males tend to have shorter sighting histories. The reproductiv e success of white-blaze males appeared similar to that of black males amon g whales off Argentina. There were significantly fewer white-blaze calves t han expected off South Africa, which could be due to white-blaze males expe riencing reduced reproductive success or to sighting biases that result in white-marked calves being misidentified as black calves, The relative frequ encies of both types of dorsal color markings varied between the South Afri can and Argentinian right whale populations, suggesting limited nuclear gen e flow between these populations; analyses using other nuclear markers are under way to confirm the extent of gene flow.