These butterflies have bright red wings to help attract mates

By Stephen Beech via SWNS

Butterflies' bright red wings help them attract mates, reveals new research.

A gene that influences visual preferences in tropical butterflies has been identified by evolutionary biologists for the first time.

Heliconius butterflies are well known for the bright color patterns on their wings.

Now researchers have found that the striking patterns not only scare off predators – the butterflies are poisonous and are distasteful to birds – but are also important signals during mate selection.

A team led by Professor Richard Merrill, from Ludwig Maximilian University of Munich, Germany, in cooperation with researchers from Colombia and Panama, has now exploited the diversity of warning patterns of various Heliconius species to investigate the genetic foundations of the preferences.

In the process, the researchers identified a gene that is directly linked to evolutionary changes in a visually guided behavior, the first time such a connection has been shown in an animal.

The team conducted hundreds of behavioral experiments to investigate the mating preferences of three Heliconius species in Colombia: Heliconius melpomene and Heliconius timareta, both of which have a bright red band on their forewing, and Heliconius cydno, which has a white forewing band.

The findings, published in the journal Science, showed that males of all three species prefer partners that look like themselves, with no differences in the preferences of the two more distantly related red species.

Using genomic analyses, the researchers showed that the preference for red females is associated with a genomic region where hybridization between the two red species has resulted in the sharing of genetic material.

PhD candidate Matteo Rossi, who conducted research on the butterflies in Merrill’s lab, said: "We managed to identify regucalcin1 as a key gene controlling visual preference, in these butterflies.

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

Further analyses by the scientists showed that regucalcin1 was transferred from H. melpomene to H. timareta sometime in their evolutionary past.

Co-lead author Professor Carolina Pardo-Diaz, of the Universidad del Rosario, Colombia, said: “We’ve known for quite a while that the red color pattern gene was introduced from one species to the other through hybridization, and suspected that the same might be true for the corresponding preference.

"To finally show it, and identify the specific gene is really exciting.

"Thanks to regucalcin1, the attractiveness of red females and thus the reproductive success of H. timareta was increased."

Merrill added: “We see differences in visual preferences all around us in nature when animals choose who to mate with.

"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 hybridization can play an important role in the evolution of these behaviors."