Hey, good looking! Gene that encodes butterflies’ mating preferences identified

Evolutionary biologists have identified a gene that encodes the visual preference for selecting a mate in tropical Heliconius butterflies.

Species in the Heliconius genus are known for their striking colour patterns, which not only deter predators – warning they are poisonous and distasteful to birds – but also play an important role in attracting and recognising suitable mates.

Researchers carried out behavioural experiments with 3 closely related species from Colombia: H.melpomene and H. timareta, which both have a bright red band on their forewing, and H. cydno, which has a white forewing band.

Their experiments, described in a paper in the journal Science, revealed that males of all 3 species prefer partners which look like themselves. Both red species, H. melpomene and H. timareta, have evolved the same preference for red wing patterns.

“We managed to identify regucalcin1 as a key gene controlling visual preference, in these butterflies,” says Matteo Rossi, an evolutionary biologist from the Ludwig Maximilian University of Munich in Germany.

“If regucalcin1 is silenced, it impairs courtship toward conspecific females, proving a direct link between gene and behaviour.”

Photograph of two black butterflies with red and white stripes on their wings flying up to an artificial feeder
Heliconius melpomene butterflies approach an artificial feeder. Credit: Carolin Bleese

The mimicry between the 2 red species was already known to have been caused by H. timareta acquiring colour-pattern genetic mutations from H. Melpomene through hybridisation. This is where 2 animals of different, but closely related, species mate to produce a hybrid offspring.

“We’ve known for quite a while that the red colour pattern gene was introduced from one species to the other through hybridisation, and suspected that the same might be true for the corresponding preference” says Carolina Pardo-Diaz, Dean of Biology at the University of the Rosary, Colombia, and one of the lead authors on the paper.

This new research indicates that regucalcin1 was also transferred from H. melpomene to H. timareta sometime in their evolutionary past.

“To finally show it, and identify the specific gene is really exciting,” says Pardo-Diaz.

Lead author Richard Merrill, an evolutionary biologist from LMU Munich, adds: “with our results, we were able to establish a direct link between a particular visual preference and a specific gene for the first time, and also demonstrate that hybridisation can play an important role in the evolution of these behaviours.”

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