Once male prairie voles have found a mate, what makes some stay at home, while others stray? The latest insight in a canonical scientific saga of genes, brain, social behavior, and evolution comes from new research from the University of Texas at Austin and published this week in Science. A perspective piece by IGB Director Gene Robinson in the same issue puts this work in historical context, and describes how the new findings have completed a circle back to classic University of Illinois study that first inspired this area of research.
“Soon after launching an ambitious 25-year study of the population cycles of rodents in the fields and prairies near the University of Illinois at Urbana–Champaign in 1971, Lowell Getz saw something strange. Adult male and female prairie voles (Microtus ochrogaster) often appeared in the same live trap, unlike the meadow vole, whose sexes were more segregated. Moreover, the same pairs were often retrapped months later. Using radio tracking, Getz and his co-workers found that most trapped pairs were long-term partners living together in underground nests and sharing common home ranges. So began almost 50 years of pathbreaking research into the biology of prairie vole monogamy, in one of fewer than 5% of mammalian species with a monogamous lifestyle.”
The perspective piece emphasizes the novelty of the new research, led by biologist Stephen Phelps and graduate student Mariam Okhovat. Phelps, Okhovat and colleagues explored the regulation of avpr1a, the gene encoding the receptor for a neurochemical signal related to mating behavior, in the brains of male prairie voles. They showed connections between differences in activity of avpr1a among individual male voles in regions of the brain involved in spatial learning, genomic mechanisms contributing to those differences, and evolutionary selection pressures that help keep two different types of males—the faithful and the unfaithful—present in the population.
“Okhovat et al. propose that high population densities favor genetic variants resulting in lower V1aR expression, poorer spatial memory, and more expansive home ranges to capitalize on enhanced possibilities of extra-pair matings. Low population densities would favor the inverse of these traits. In other words, the evolutionary explanation . . . points to the very same cycles of population density that originally motivated Getz's field studies. The study by Okhovat et al. impressively bridges mechanistic and evolutionary analyses to provide a detailed picture of individual differences in social behavior.”