According to new research reported in the journal Nature Communications, light-colored insects are out-competing darker-colored ones in the face of climate change.
The Southern Small White (Pieris mannii) in Madrid, Spain.
“When studying biodiversity, we lack general rules about why certain species occur where they do. With this research we’ve been able to show that butterfly and dragonfly species across Europe are distributed according to their ability to regulate heat through their color variation,” said study lead author Dr Dirk Zeuss from Philipps-University Marburg, Germany.
The color of an insect’s body plays a key role in how they absorb energy from the Sun, and is crucial in fuelling their flight as well as regulating the temperature of their body.
Dark-colored insects are able to absorb more sunlight than light-colored insects, in order to increase their body temperature, and are more likely to be found in cooler climates.
In contrast, insects in hotter climates need to protect themselves against overheating.
Light-colored insects are more likely to be found in hotter climates as they can reflect the light to prevent overheating their body and be active for longer periods of time.
To identify whether color lightness was correlated to temperature, a group of researchers led by Dr Stefan Brunzel of Philipps-University Marburg combined digital image analysis with distributional data which mapped where European species of butterflies and dragonflies are found.
The scientists looked at 366 butterfly species and 107 dragonfly species, and showed a clear pattern of light-colored insects dominating the warmer south of Europe and darker insects dominating the cooler north.
For example, several Mediterranean dragonfly species have expanded their northern range and immigrated to Germany, such as the Southern Migrant Hawker (Aeshna affinis), the Scarlet Darter (Crocothemis erythraea) and the Dainty Damselfly (Coenagrion scitulum).
In 2010, the Dainty Damselfly was also sighted in England for the first time in over 50 years.
Butterfly species that thrive in warm climates, like the Southern Small White (Pieris mannii), have dispersed to Germany during the last ten years and are still continuing their northward shift.
“For two of the major groups of insects, we have now demonstrated a direct link between climate and insect color, which impact their geographical distribution,” said co-author Prof Carsten Rahbek of Imperial College London.
To test whether a warming climate had caused any shifts, the team looked at changes in species distributions over an 18-year period from 1988-2006.
Results showed that on average insects were becoming lighter in color, and that darker-colored insects were shifting towards the cooler areas in Western margins of Europe, the Alps and the Balkans.
“Until now we could only watch the massive changes in the insect fauna during the last 20 years. Now we have an idea of what could be a strong cause of the changes,” Dr Brunzel concluded.
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Dirk Zeuss et al. 2014. Global warming favours light-coloured insects in Europe. Nature Communications 5, article number: 3874; doi: 10.1038/ncomms4874
