A Shrinking Feeling for Butterflies

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Ongoing climate change has had a variety of effects on global ecosystems and species, and now recent research from Aarhus University has unearthed a worrying size trend in Greenland butterflies. 

By measuring the wing length of approximately 4,500 individual butterflies between 1996 and 2013 scientists have found that warmer summer temperatures are correlated with smaller butterfly sizes in two different species. This is one of the few studies at present which follows physiological changes across a period of climactic change and despite theory predicting body size changes in response to changing climate; it is one of the few field studies that have demonstrated a such a response.

Arctic fritillary (Boloria chariclea) is one of the species studied by scientists that has decreased in size due to changing climate.
Arctic fritillary (Boloria chariclea) is one of the species studied by scientists that has decreased in size due to changing climate.

However, the direction of this response is variable across species. Climate change might lengthen a period of favorable conditions, allowing an organism to grow to larger sizes. However, it might also shorten a period of favorable conditions, or change metabolic rate and in doing so, reduce the growth of an organism.

In this particular case, the cold blooded nature of these butterfly larvae is responsible for their decreased size under warmer temperatures. The increased temperature speeds up the metabolic rate of the larvae who have no means to regulate their temperature.

As a result they are losing more energy than they are gaining by feeding, meaning that the larvae are smaller when they undergo metamorphosis, resulting in smaller adults.

Size is incredibly important in the animal kingdom, and in this case can limit the mobility of butterflies. This is important under changing climate as it might prevent the animals from moving to cooler conditions, and can also impact on how many young they have.

Other species from a wide variety of taxa have shifted their range in response to climate, however the reduced mobility of these butterflies means that they may face extinction.

 

Featured Image from Wikimedia Commons

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I'm a newly arrived PhD student of ocean and earth science at the national oceanography centre. I have a passion for wildlife, the environment and the beauty and power of evolutionary theory.

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