Balancing selection maintains polymorphisms at neurogenetic loci in field experiments
Lonn, E., Koskela, E., Mappes, T., Mökkönen, M., Sims, A., & Watts, P. (2017). Balancing selection maintains polymorphisms at neurogenetic loci in field experiments. Proceedings of the National Academy of Sciences of the United States of America, 114 (14), 3690-3695. doi:10.1073/pnas.1621228114
Date
2017Discipline
Ekologia ja evoluutiobiologiaCopyright
© the Authors, 2017. Freely available online through the PNAS open access option.
Most variation in behavior has a genetic basis, but the processes
determining the level of diversity at behavioral loci are largely
unknown for natural populations. Expression of arginine vasopressin
receptor 1a (Avpr1a) and oxytocin receptor (Oxtr) in specific regions
of the brain regulates diverse social and reproductive behaviors in
mammals, including humans. That these genes have important fitness
consequences and that natural populations contain extensive diversity
at these loci implies the action of balancing selection. In Myodes
glareolus, Avpr1a and Oxtr each contain a polymorphic microsatellite
locus located in their 5′ regulatory region (the regulatory regionassociated
microsatellite, RRAM) that likely regulates gene expression.
To test the hypothesis that balancing selection maintains diversity
at behavioral loci, we released artificially bred females and males
with different RRAM allele lengths into field enclosures that differed
in population density. The length of Avpr1a and Oxtr RRAMs was
associated with reproductive success, but population density and the
sex interacted to determine the optimal genotype. In general, longer
Avpr1a RRAMs were more beneficial for males, and shorter RRAMs
were more beneficial for females; the opposite was true for Oxtr
RRAMs. Moreover, Avpr1a RRAM allele length is correlated with
the reproductive success of the sexes during different phases of reproduction;
for males, RRAM length correlated with the numbers of
newborn offspring, but for females selection was evident on the
number of weaned offspring. This report of density-dependence
and sexual antagonism acting on loci within the arginine vasopressin–oxytocin
pathway explains how genetic diversity at Avpr1a and
Oxtr could be maintained in natural populations.
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