Ancient DNA provides clues to the evolution of social behaviour
The colonial tuco-tuco (Ctenomys sociabilis)
“A rare Patagonian rodent known as the colonial tuco-tuco fascinates biologists because it seems to defy all odds. This threatened species has so little genetic diversity that the slightest whiff of climate change or disease should have wiped it off the face of the earth long ago. Yet the hearty gopher-like creature has not only managed to survive for thousands of years in the harsh climate of the Argentine highlands, it has evolved a complex social structure that’s unique among the more than 50 closely related tuco-tuco species.”
Analysis of ancient and modern DNA allowed the researchers to track tuco-tuco populations over the last 10,000 years, as the population of the colonial species was slowly reduced by competition with a larger species. Suddenly, 3,000 years ago, over 99 percent of the colonial species vanished at a time of major Andean volcanic activity, leaving only about 300 females behind (with an undetermined number of males) — resulting in an evolutionary bottleneck. Since then, the population has bounced back.
No one knows exactly when social behavior evolved in C. sociabilis, but the researchers suspect it was a response to the population crash.
“Maybe the evolution of sociality actually confers some advantage to withstanding periods of low genetic diversity. Most behaviorists would say that sociality is so complicated that it takes a while to evolve, but maybe if a species has to be social to survive, social behavior could evolve pretty rapidly.” – Elizabeth Hadly
I’d be reluctant to speculate about the influence of population bottlenecks on the evolution of social behaviour in other species — but it’s certainly interesting research.