Heat “may speed mammal evolution”

Climate could have a direct effect on the speed of “molecular evolution” in mammals, according to a study that could help explain why the tropics are so rich in species. In the study published in Proceedings of the Royal Society B, the BBC reported, researchers found that – among pairs of the same species -- the DNA of those living in warmer climates changes at a faster rate.

DNA can mutate and change imperceptibly every time a cell divides and makes a copy of itself. But when a mutation causes a change that is advantageous for the animal, it is often “selected for”, or passed down to the next few generations of that species.

The idea that such “microevolution” happens faster in warmer environments is not new. But the study – led by Len Gillman from Auckland University of Technology – marks the first time that the effect has been shown in mammals, which regulate their own body temperature.

“The result was unexpected,” Gillman told the BBC. “We have previously found a similar result for plant species, and other groups have seen it in marine animals.” But since the body temperature of those life forms is controlled directly by the environment , “everyone assumed that the effect was caused by climate altering their metabolic rate”.

Scientists believe that the link between temperature and metabolic rate means that, in warmer climates, the cells that eventually develop into sperm and eggs divide more frequently. Gillman and his team compared the DNA of 130 pairs of “sister species” mammals, where each of the pair lived at a different latitude or elevation. The research results support the idea that high tropical biodiversity is caused by faster rates of evolution in warmer climates.

See full story