Evolution faster in the tropics

29 Jun, 2009
Lemurs painting

Led by AUT University evolutionary biologist Len Gillman, the team was also made up of researchers from the School of Biological Sciences at the University of Auckland, including Dr Shane Wright, whose earlier work was highly influential in establishing differing evolution rates between plants in different climates.

In this and previous work, Wright’s research has been supported by Ngā Pae o te Māramatanga, the Māori Centre of Research Excellence.

Gillman says the rate of evolution was markedly different, and over prolonged evolutionary periods of time, this difference in evolutionary rate might account for the enormous accumulation of biodiversity in warmer areas like the tropics.

“The results show that species occupying warmer climates have almost 50% more DNA evolution relative to those in cooler climates. These results come from pairs of species generally living in close proximity to each other so we would expect the effect to be far more pronounced over continental and global scales.”

Gillman’s research has also identified potential negative evolutionary consequences of scarce basic resources related to available energy supply.

Australasian marsupials in the study showed less significant increases in their rates of evolution when compared to their counterparts living in cooler climates and it is thought that this might be linked to the drought conditions in the warmer environments of Australia.

Gillman says there are indications that the slowed rates of evolution may be due to periods of hibernation or inactivity of animals living in cooler environments.

“Earlier research we carried out identified faster rates of DNA evolution in plants living in tropical regions but other scientists did not believe that climate could possibly have any bearing on mammal evolution given their constant body temperatures.”

“These results provide support for the hypothesis that high tropical species richness is caused by faster rates of evolution and speciation in warmer climates.”

The study, which is the largest of its kind, involved a comprehensive global data set that included 260 mammal species, from 10 orders and 29 families.

The research findings of Len Gillman and Shane Wright have today been published internationally in the Royal Society’s biological research journal Proceedings B.

For more information, please contact:

Len Gillman, BSc. PhD.
Senior Lecturer, Evolutionary Ecology
AUT University
Phone 64 9 921 9999 extn 8213
A/H 09 817 1979

Why evolution moves faster in the tropics

How could the evolution of already warm-blooded animals be affected by warmer weather?

Keeping up with the Joneses – the Red Queen hypothesis suggests that species in an ecosystem must continue to evolve in order to stay where they are relative to the species evolving around them. In other words, says Gillman, because plants and animals that don't set their own body temperature may have faster evolutionary rates in the tropics, the mammals are evolving faster too, to keep up.

Less lazy Wintry behaviours – in cold, less productive environments where basic resources such as food are more limited, adaptive mammal behaviours designed to conserve energy like hibernation or lying about may reduce their metabolic activity. In warmer environments metabolic activity is likely to be greater and this is thought to increase the number of mutations. With an increase in the number of mutations, the tiny proportion that have an adaptive advantage will also increase, thereby increasing the overall pace of evolution.

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