Study: Climate dictates size and color of resident ants

"These results will help us to understand why ant species are distributed in the way that they are across the globe," said ecologist Tom Bishop.

By Brooks Hays

LIVERPOOL, England, Sept. 8 (UPI) -- Ants in colder environs tend to be bigger and darker in color, while ants in warmer climes are typically smaller and paler in color. That's the conclusion of a new study which looked at how the environment influences the physiological traits of local ant colonies.

For seven years, scientists at the University of Liverpool studied the makeup of ant communities at 14 different mountainous sites in South Africa, South America and Australia, noting size, color and species abundance. They found ants living closer to the poles or the tops of mountains, where temperatures are lower, were mostly dark black and large in size.


Because ants are ectotherms and rely on external temperatures to dictate their metabolism, retaining heat in cold climes is important. Darker colors help ants absorb heat more efficiently, while larger bodies help them retain that heat.

But temperature wasn't the only factor that affected color. Researchers found higher levels of UV-B radiation also encouraged darker colors, as melanin, the pigment that gives ants their black color, also protects against harmful radiation.

Scientists found dark-colored ants in the sun-soaked Australian desert, where the warm temperatures should have promoted lighter colors.


These correlations where consistent across continents and even from year to year. During warmer years, scientists found a greater abundance of light-colored ants, and vice versa during warmer years.

Researchers published their findings in the journal Global Ecology and Biogeography.

"Our results have two key messages," lead researcher Tom Bishop said in a news release. "First, that the environment has a really strong influence on the identities and relative abundances of the ant species that you may find at a given location -- this is mediated by the coloration and size of those different species."

"Secondly, these effects can operate over across mountains and continents but also across short time periods," Bishop continued. "These results will help us to understand why ant species are distributed in the way that they are across the globe, but also highlight that as the climate changes there may be certain ways in which the ants respond."

As the planet warms, lighter-colored, smaller ant species are likely to proliferate, which could have cascading effects on local ecosystems.

"Our findings could be applied to many other insect or ectotherm groups too and could explain a lot of the observed color and body size diversity patterns globally," added Kate Parr, co-author and Liverpool ecologist.


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