Key Insights – Watts et al. 2017

Watts, P.C., E.R.K. Kallio, E. Koskela, E. Lonn, T. Mappes & M. Mokkonen. Stabilising selection on microsatellite allele length at arginine vasopressin 1a receptor and oxytocin receptor loci. Proceedings of the Royal Society B: Biological Sciences 284: 20171896.

OVERVIEW:
This study utilized a laboratory colony of bank voles (Myodes glareolus) to assess whether selection was operating on the length of microsatellite alleles in the regulatory regions of two important genes, Oxtr and Avpr1a, that are known to influence socio-reproductive behaviours and fitness. The lengths of these alleles are generally associated with the level of gene expression, and thus, provide a direct link between genotype and phenotype. Adult females and males were paired in the laboratory and the probability of breeding was assessed. We conclude that stabilizing selection is acting on the Avpr1a and Oxtr microsatellite polymorphisms, with the ends of the allele length distributions being selected against.

NOVEL FINDINGS:
-there was selection for intermediate length Avpr1a alleles in females
-there was selection for more homogeneous genotypes (i.e. more similar allele lengths for the two copies in genotype) for male Avpr1a and female Oxtr
-greater dissimilarity in Oxtr genotypes between males and female pairs was associated with lower breeding success

OTHER NOTABLE DETAILS:
-the Oxtr locus may serve a function in assortative mating in this species, given the decreased breeding success associated with genetic dissimilarity between partners at this locus
-we hypothesize that stabilizing selection is acting on the extreme (short and long) lengths of the allele distributions for Avpr1a and Oxtr, while balancing selection is acting on more immediate lengths to maintain genetic variation.