TitleRainfall-driven sex-ratio genes in African buffalo suggested by correlations between Y-chromosomal haplotype frequencies and foetal sex ratio.
Publication TypeJournal Article
Year of Publication2010
Authorsvan Hooft, P, Prins, HHT, Getz, WM, Jolles, AE, van Wieren, SE, Greyling, BJ, van Helden, PD, Bastos, ADS
JournalBMC Evol Biol
Date Published2010 Apr 23
KeywordsAnimals, Buffaloes, Climate, Female, Fetus, Haplotypes, Male, Microsatellite Repeats, Sex Ratio, South Africa, Y Chromosome

BACKGROUND: The Y-chromosomal diversity in the African buffalo (Syncerus caffer) population of Kruger National Park (KNP) is characterized by rainfall-driven haplotype frequency shifts between year cohorts. Stable Y-chromosomal polymorphism is difficult to reconcile with haplotype frequency variations without assuming frequency-dependent selection or specific interactions in the population dynamics of X- and Y-chromosomal genes, since otherwise the fittest haplotype would inevitably sweep to fixation. Stable Y-chromosomal polymorphism due one of these factors only seems possible when there are Y-chromosomal distorters of an equal sex ratio, which act by negatively affecting X-gametes, or Y-chromosomal suppressors of a female-biased sex ratio. These sex-ratio (SR) genes modify (suppress) gamete transmission in their own favour at a fitness cost, allowing for stable polymorphism.

RESULTS: Here we show temporal correlations between Y-chromosomal haplotype frequencies and foetal sex ratios in the KNP buffalo population, suggesting SR genes. Frequencies varied by a factor of five; too high to be alternatively explained by Y-chromosomal effects on pregnancy loss. Sex ratios were male-biased during wet and female-biased during dry periods (male proportion: 0.47-0.53), seasonally and annually. Both wet and dry periods were associated with a specific haplotype indicating a SR distorter and SR suppressor, respectively.

CONCLUSIONS: The distinctive properties suggested for explaining Y-chromosomal polymorphism in African buffalo may not be restricted to this species alone. SR genes may play a broader and largely overlooked role in mammalian sex-ratio variation.

Alternate JournalBMC Evol Biol
PubMed ID20416038
PubMed Central IDPMC2875233
Grant ListGM83863 / GM / NIGMS NIH HHS / United States