Descobrindo como as borboletas escolhem seus parceiros

The study investigates the neural circuits and genes involved in how Heliconius butterflies choose their butterfly partners. These butterflies prefer mates that resemble them, even among closely related species which have markedly different patterns, ecosystems and behaviors. The researchers aim to understand how these behavioral patterns are encoded in the brain and contribute to species diversification.

José Borrero, a graduate student from Richard Merrill's lab at Ludwig Maximilian University, explains their focus in collaboration with Carolina Pardo-Díaz, a professor of evolutionary genetics, phylogeography and ecology at the Universidad del Rosario in Bogotá, and Camilo Salazar, also a professor at the same department. Colombia boasts an extraordinary density of Heliconius species, with distinct populations on either side of the Andes mountain range, making it ideal for studying how habitat differences shape the butterfly's brain, behavior, and genetics.

One single genetic locus explains about 30% of the difference in partner preference between two species, a surprisingly large effect for such a complex behavior as mate choice. The genes responsible for partner preference are physically close in the genome to those that control wing patterns, suggesting they are inherited together and help populations remain distinct even when crossed.

These genetic sets can cross species boundaries through hybridization, leading to behavioral preferences and color patterns across lineages. The lab now wants to understand how these genetic differences translate into brain differences. Their collaboration has shown that the butterfly's brain continues to develop after it emerges from the chrysalis, and for this reason, adult butterflies see significantly better than newly emerged ones.

The optic lobes, which process visual information, continue growing throughout the animal's life, according to a preprint. Species living in darker, more complex forest interiors have larger optic lobes and better visual acuity, and rely more on sight than smell when foraging. The study found that males only start looking for mates once their brain and visual capacity have matured.

Fieldwork takes place at a research station near Bogotá, where butterflies are kept in large, outdoor cages located right next to the cloud forest where these species live. The cages are installed close enough for the animals to experience the same light, temperature and vegetation found in their natural environment. This setup is essential for the experiments: butterflies tested under the laboratory's white light, without the ultraviolet wavelengths they use to perceive their surroundings, perform very poorly.

Borrero notes that to truly understand how the butterflies behave, it is crucial to test them in the environment where these behaviors actually occur.