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Rate of molecular evolution of the seminal protein gene SEMG2 correlates with levels of female promiscuity


Postcopulatory sperm competition is a key aspect of sexual selection and is believed to drive the rapid evolution of both reproductive physiology and reproduction-related genes1,2,3,4. It is well-established that mating behavior determines the intensity of sperm competition, with polyandry (i.e., female promiscuity) leading to fiercer sperm competition than monandry1,2,3. Studies in mammals, particularly primates, showed that, owing to greater sperm competition, polyandrous taxa generally have physiological traits that make them better adapted for fertilization than monandrous species, including bigger testes, larger seminal vesicles, higher sperm counts, richer mitochondrial loading in sperm and more prominent semen coagulation2,5,6,7,8. Here, we show that the degree of polyandry can also impact the dynamics of molecular evolution. Specifically, we show that the evolution of SEMG2, the gene encoding semenogelin II, a main structural component of semen coagulum, is accelerated in polyandrous primates relative to monandrous primates. Our study showcases the intimate relationship between sexual selection and the molecular evolution of reproductive genes.

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Figure 1: Lineage-specific ω values of SEMG2 in primates, calculated using the SEMG2 coding region before the stop codon present in the chimpanzees, which occurs earlier than in the other primates17.
Figure 2: Correlation between the rate of evolution of SEMG2 and reproductive behavior and physiology in primates.
Figure 3: Sliding-window analysis of ω values in the common chimpanzee lineage and the crab-eating macaque lineage.

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We thank W.-H. Huang for technical assistance; A. Di Rienzo, C. Malcom, N. M. Pearson, E. J. Vallender and C.-I Wu for discussions and comments on the manuscript; and L.G. Chemnick, A.R. Ryder and L. Faust for providing primate tissue samples. This work was supported in part by the William Rainey Harper Fellowship (to S.D.) and the Searle Scholarship and the Burroughs Wellcome Career Award (to B.T.L.).

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Correspondence to Bruce T Lahn.

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Supplementary information

Supplementary Fig. 1

Lineage-specific ω values of SEMG2 in primates. (PDF 9 kb)

Supplementary Fig. 2

Correlation between the evolutionary rate of SEMG2 and the reproductive behavior/physiology in primates. (PDF 13 kb)

Supplementary Table 1

Likelihood estimates of different evolutionary models. (PDF 9 kb)

Supplementary Table 2

Likelihood ratio between different evolutionary models. (PDF 8 kb)

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Dorus, S., Evans, P., Wyckoff, G. et al. Rate of molecular evolution of the seminal protein gene SEMG2 correlates with levels of female promiscuity. Nat Genet 36, 1326–1329 (2004).

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