It is beneficial for butterfly species with large brains to survive

Evolutionary developments and changes to the brain system give rise to animal behavior, senses, and cognitive abilities. Animals’ neurological systems have developed to enable them to feel and engage with their environment. Models of brain evolution place a strong emphasis on the coordinated evolution of networks that are functionally coupled, with localized specialization concentrating on enhancing existing functions.

Compared to their close relatives, they have a mushroom-shaped brain region known as the mushroom body that is two to four times larger. A recent study found a direct connection between an organism’s behavior and ecological niche and the structure and function of its brain system.

Heliconius are the only butterflies known to gather and digest pollen, giving them an adult source of protein when most other butterflies only receive protein as larvae, according to Dr. Stephen Montgomery of Bristol’s School of Biological Sciences.

The only butterflies known to collect and digest pollen and have long lifespans are Heliconius butterflies. They can only gather pollen from a small number of low-density plant species, though. Since knowing the locations of these plants is a key behavior for them, they must spend more heavily in the brain networks and cells that support spatial memory.

The focus of the study was on the connection between sensory specialization, body growth, and the pollen eating evolutionary adaptation. They created 3D models of the brains of 11 species from closely related genera and 30 species of pollen-eating Heliconius species collected from Central and South America.

By measuring the sizes of different brain regions and mapping them onto phylogenetic trees, it was possible to determine the locations of significant evolutionary changes in the makeup of the brain.

They subsequently studied sensory specialization by counting the number of neurons in the mushroom bodies and the density of their connections, and tracing neural inputs from brain regions that process visual and olfactory information before transmitting it to the central brain.

In order to determine whether the mushroom body’s apparent expansion was related to improved visual learning and memory, they collaborated with the Smithsonian Tropical Research Institute in Panama to conduct behavioral research on significant species.

The amazing range of mushroom body size variation found among these closely related species over a short evolutionary period is one noteworthy effect. Over the course of the entire dataset, the mushroom’s size varies by a factor of 25.

This offers a fascinating example of how different brain regions can develop independently over the course of evolution, a process known as mosaic evolution when faced to intense selective pressures for behavioral adaptation.

“We identified that changes in mushroom body size are due to an increased number of Kenyon cells, the neurons that make up the majority of the mushroom body and whose interactions are thought to be the foundation of memory storage,” he continued. “We also identified that changes in mushroom body size are due to increased inputs from the visual system.”

According to the University of Bristol researcher, “This mushroom bodies’ growth and visual specialization were accompanied by improved visual learning and memory abilities. By combining several data types, we can clearly show how a novel foraging habit can coexist with brain adaptations and related cognitive changes.

According to the new research, the Heliconius butterfly’s brain structure, notably the mushroom bodies, has undergone significant changes that are directly tied to their specific foraging behaviors. These butterflies can discriminate between complex visual patterns and preserve long-term memory thanks to their bigger mushroom bodies and better visual processing abilities. These research projects highlight the interesting connection between behavioral adaptations in the natural world and brain evolution.

“This study provides a rare combination of neurobiological and behavioral data across closely related species, revealing a clear example of marked evolutionary changes in the brain over a relatively short time scale coinciding with improved visual learning and memory abilities,” said Dr. Fletcher Young, who is also a co-lead author. Understanding how brain changes and behavioral changes are related is essential to our comprehension of cognitive evolution.

Understanding the relationship between brain anatomy, sensory processing, and foraging behavior in Heliconius butterflies may shed light on how learning and memory mechanisms have evolved in insects and other animals, as the function and circuitry of mushroom bodies share some similarities with vertebrate brains.

“We provide evidence that brain structure can vary strikingly between closely related species living in the same habitats,” said Dr. Montgomery in his conclusion.