JAN 08, 2019 7:55 AM PST

A Genetic Recipe for Monogamy

WRITTEN BY: Carmen Leitch

Is it natural to remain committed to a mate for life? Researchers at the University of Texas Austin have used genetics to learn more about monogamy. After assessing ten different vertebrate species, they found that monogamous animals have shared gene expression patterns. The researchers suggested that a universal recipe underlies the evolution of monogamy in vertebrate species. The findings have been reported in the Proceedings of the National Academy of Sciences (PNAS).

Non-monogamous female do most of the parenting, and in monogamous species, it's often shared. These frogs move tadpoles after hatching to water. In the non-monogamous strawberry poison frog (Oophaga pumilio, left) moms do it; in the monogamous mimic poison frog (Ranitomeya imitator, right) dad does the job. / Credit: Yusan Yan and James Tumulty

"Our study spans 450 million years of evolution, which is how long ago all these species shared a common ancestor," said the first author of the study, Rebecca Young, a research associate in UT Austin's Department of Integrative Biology.

For this study, the researchers called animals monogamous if they formed a pair bond with one mate through at least one mating season, and in some way shared the rearing and protection of offspring. In a bit of a loosening of the definition, animals were still considered monogamous even when they mated with another animal occasionally.

The scientists used using RNA-sequencing technology to analyze tissue samples from the species they selected, and reveal the active genes in those samples. Five pairs of species that were closely related were assessed - two fish, two frogs, two birds, and four mammals; for each species one member was monogamous, and one was not. Monogamy has evolved independently five times, and the five pairs were meant to represent those events. For example, these close relatives - monogamous prairie voles and non-monogamous meadow voles, which diverged at one time into different species.

In all ten species, the researchers looked at the active gene expression in the brains of the males, then used bioinformatics to detect patterns. They focused on the evolutionary changes in the animals that were very similar to each other. Based on similarities in the sequences, the researchers could group genes from species that were distantly related. They found a common evolutionary recipe that generated bonded pairs and co-parenting behaviors in the five monogamous species.

Although monogamy is a very complex behavior, the same gene expression changes were happening every time in different animals. The scientists suggested that there is a similar mechanism underlying the evolution of monogamy through changes in the transcriptome - the active genes. "Most people wouldn't expect that across 450 million years, transitions to such complex behaviors would happen the same way every time," Young said.

At least five times during the past 450 million years, evolution used a kind of universal formula for turning animals monogamous by increasing some gene activity (red) and decreasing others (blue) in the brain. / Credit: University of Texas at Austin

This work covers a longer timespan than previous studies; it spanned hundreds of millions instead of tens of millions of years of evolution.

You can learn more about research done on voles, and a follow-up study with humans that assessed whether monogamy had a genetic component, from this video by McGill University.

Sources: AAAS/Eurekalert! via University of Texas at Austin, PNAS

About the Author
Bachelor's (BA/BS/Other)
Experienced research scientist and technical expert with authorships on over 30 peer-reviewed publications, traveler to over 70 countries, published photographer and internationally-exhibited painter, volunteer trained in disaster-response, CPR and DV counseling.
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