Habitat shifts change the brain structure of butterflies

A recent study led by the University of Bristol has found that habitat shifts in populations of Amazonian butterflies accurately predict changes in their brain structures, particularly in areas that process visual information. These findings provide strong evidence that habitat shifts are adaptive and that local adaptation to distinct light environments can occur at very small ecological scales.

“It was known that niche partitioning in complex habitats, like tropical rainforests, might pose perceptual challenges for the animals living in them,” said study lead author Benito Wainwright, a biologist at the University of Bristol. “Work on fish in freshwater ecosystems had previously shown that dramatic changes in light availability with depth can result in impressive visual adaptations, but little was known whether evolution could select for such adaptations in a terrestrial environment like a tropical forest.”

The scientists studied 160 samples across 16 species of Amazonian butterflies belonging to the Neotropical tribe called Ithomiini. The sample size makes this the largest neuroanatomical comparison undertaken for any type of insect. Habitat shifts were indicated by changes in mimicry patterns. 

The results highlight the importance of visual ecology in adaptively shaping entire communities of closely related species in complex terrestrial ecosystems.  In future research, the scientists aim to investigate sensory evolution across the entire community of butterflies to rigorously assess whether convergence in habit always predicts convergence in brain structure.  

“In other words, we want to know whether when faced with the same perceptual challenges, species evolve sensory adaptations via similar mechanisms,” Dr. Wainwright explained. “We also wish to quantify the light environment within these forests to investigate to what degree small changes in forest structure affect the sensory environment.”    

Since Ithomiine butterflies play a crucial role in a large variety of tropical ecosystems, understanding their evolutionary responses can help make more accurate predictions on how sudden changes in the sensory environment may affect the composition of entire rainforests.

“Our work shows that the way species have evolved to process the world around them plays an important role in the way entire animal communities are structured. Natural selection can lead to adaptive change in brain structure over relatively short periods of evolutionary time,” Dr. Wainwright concluded.

The study is published in the journal Ecology.

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By Andrei Ionescu, Earth.com Staff Writer