Meeting Abstract

106.1  Tuesday, Jan. 7 08:15  Regulating monogamy: evidence for adaptive evolution of an avpr1a enhancer BERRIO, A; OKHOVAT, M; O’CONNELL, L; PHELPS, SM*; University of Texas; University of Texas; University of Texas, Harvard; University of Texas sphelps@mail.utexas.edu

Voles are important models for the molecular mechanisms of social behavior. Species differences in mating system are shaped by the expression of vasopressin receptors (V1aR) in reward-related brain regions. We examined the evolution of brain and behavior by sequencing the avpr1a locus and several neutral loci from 8 species of New World Microtus, using Myodes gapperi as an outgroup. Of these, two species are socially monogamous (M. ochrogaster and M. pinetorum), and the remaining taxa are promiscuous. Remarkably, M. ochrogaster and M. pinetorum were found to be sister taxa (post. prob.=0.99), indicating monogamy evolved a single time within this clade. This novel pairing suggests the elevated expression of V1aR both species exhibit in the ventral pallidum, a reward region that governs pairbonding, is homologous rather than convergent. To identify cis-regulatory changes associated with this phenotype, we examined ~7kb of avpr1a non-coding sequence, spanning from ~2.6kb 5’ of the translation start site to ~1.5kb 3’ of the avpr1a stop codon. We found a total of three microsatellite sequences, none of which were reliably associated with mating system. However, a short region of non-repetitive 5’ sequence exhibited evidence of accelerated evolution that coincided with the onset of monogamy (LRT, P<0.01). Furthermore, preliminary ChIP-seq data targeting H3K4me1, a marker of enhancers, suggests the site gained function as an enhancer of expression in the ventral pallidum. Lastly, an HKA test indicates reduced standing variation at this putative enhancer. Together the data demonstrate how changes in cis-regulation can drive adaptive changes in gene expression and social behavior.