Balancing selection maintains polymorphisms at neurogenetic loci in field experiments.
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. InMyodes glareolus,Avpr1aandOxtreach contain a polymorphic microsatellite locus located in their 5' regulatory region (the regulatory region-associated 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 ofAvpr1aandOxtrRRAMs was associated with reproductive success, but population density and the sex interacted to determine the optimal genotype. In general, longerAvpr1aRRAMs were more beneficial for males, and shorter RRAMs were more beneficial for females; the opposite was true forOxtrRRAMs. Moreover,Avpr1aRRAM 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 atAvpr1aandOxtrcould be maintained in natural populations.
Department of Biological and Environmental Science, University of Jyvaskyla, Fl-40014 Jyväskylä, Finland; eija.lonn@jyu.fi.
Eija
E
Lonn
Department of Biological and Environmental Science, University of Jyvaskyla, Fl-40014 Jyväskylä, Finland.
Esa
0000-0002-9418-5733
E
Koskela
Department of Biological and Environmental Science, University of Jyvaskyla, Fl-40014 Jyväskylä, Finland.
Tapio
T
Mappes
Department of Biological and Environmental Science, University of Jyvaskyla, Fl-40014 Jyväskylä, Finland.|Department of Biological Sciences, Simon Fraser University, Burnaby, BC V5A 1S6, Canada.
Mikael
M
Mokkonen
Department of Biological and Environmental Science, University of Jyvaskyla, Fl-40014 Jyväskylä, Finland.
Angela M
AM
Sims
Department of Biological and Environmental Science, University of Jyvaskyla, Fl-40014 Jyväskylä, Finland.|Department of Ecology and Genetics, University of Oulu, FI-90014 Oulu, Finland.
Phillip C
PC
Watts
D000818:Animals; D003411:Arvicolinae / Q000235:genetics / Q000502:physiology*; D005260:Female; D005786:Gene Expression Regulation; D056084:Genetic Fitness; D008297:Male; D018895:Microsatellite Repeats; D018045:Receptors, Oxytocin / Q000235:genetics*; D017483:Receptors, Vasopressin / Q000235:genetics*; D012045:Regulatory Sequences, Nucleic Acid; D012098:Reproduction
D018045:Receptors, Oxytocin; D017483:Receptors, Vasopressin
Avpr1a; Myodes glareolus; Oxtr; density-dependent selection; sexual conflict