Biology subjects

Melo-Florez, L.

Publications and source records attributed to Melo-Florez, L..

4 recordsLinked to original sources

bioRxiv2023

Adaptive introgression of a visual preference gene

Visual preferences are important drivers of mate choice and sexual selection, but little is known of how they evolve at the genetic level. Here we take advantage of the diversity of bright warning patterns displayed by Heliconius butterflies, which are also used during mate choice. We show that two Heliconius species have evolved the same visual mating preferences for females with red patterns by exchanging genetic material through hybridization. Extensive behavioral experiments reveal that male preferences are associated with a genomic region of increased admixture between these two species. Variation in neural expression of regucalcin1, located within this introgressed region, correlates with visual preference across populations, and disruption of regucalcin1 with CRISPR/Cas9 impairs courtship towards conspecific females, proving a direct link between gene and behavior. Our results support a role for hybridization during behavioral evolution, and show how visually-guided behaviors contributing to adaptation and speciation are encoded within the genome.

evolutionary biology↗

bioRxiv2023

Enhanced long-term memory and increased mushroom body plasticity in Heliconius butterflies

As highly labile structures on both individual and evolutionary time-scales, the mushroom bodies, a key site of learning and memory in insects, are an excellent model for investigating the evolution of cognitive variation. We explored the behavioural consequences of mushroom body expansion in Heliconius butterflies, which possess greatly expanded mushroom bodies relative to their closest outgroups. We conducted long-term visual memory assays across three Heliconius and three other Heliconiini species using trained food-colour associations. We confirm robust differences between clades, with Heliconius exhibiting greater fidelity to the trained colour after 8 days without reinforcement compared to other Heliconiini, with further evidence of stable preferences at 13 days. We extended this analysis to consider the plastic response of the mushroom body calyces over this time period, measuring the volume of the mushroom body calyx, and the number of neurons and synapses it contains. We find substantial post-eclosion expansion and synaptic pruning in calyx of Heliconius erato, but not in Dryas iulia. In Heliconius erato, visual associative learning experience specifically is associated with a greater retention of calyceal synapses. At an individual level, fidelity to the trained colour in Heliconius erato was also positively correlated with synapse number. These results point to an enhanced visual long-term memory across Heliconius, facilitated not only by phylogenetic expansion of the mushroom body, but also changes in its developmental response to learning experience. The co-evolution of mushroom body expansion, plasticity and specific behaviours provides an important case study in the evolution of cognition. Significance StatementHow are cognitive differences between species supported by evolutionary changes in the brain? We investigated this question using Heliconius butterflies which have expanded mushroom bodies, a region of the insect brain involved in learning and memory. We show that Heliconius have more stable visual long-term memories and exhibit more substantial age- and experience-related plasticity than a closely related genus with smaller mushroom bodies. Recall accuracy was also predicted by synapse number in Heliconius erato, but not Dryas iulia, suggesting functional importance. These results suggest that increases in the size of specific brain regions and changes in their plastic response to experience may co-evolve to shape the evolution of cognition.

animal behavior and cognition↗

bioRxiv2023

Reversal learning of visual cues in Heliconiini butterflies

The mushroom bodies, an integrative region of the insect brain involved in learning and memory, have undergone volumetric increase in several independent lineages includes bees and ants, cockroaches and some beetles. However, the selective pressures driving these expansion events are not fully understood. One promising system for investigating this question is the Neotropical butterfly genus Heliconius, which exhibits markedly enlarged mushroom bodies compared with other members of the Heliconiini tribe. Notably, this neural elaboration co-occurs with the evolution of trapline foraging behaviour and an improved capacity for learning complex visual cues and long-term memory. Here, we further investigate the behavioural consequences of this brain expansion by testing reversal learning ability, a commonly used measure of cognition and behavioural flexibility in both vertebrates and invertebrates, across three Heliconius and three closely-related Heliconiini species. We trained butterflies to associate a food reward with either purple or yellow flowers, before training them with the reversed associations, and then reversing the cues again. All six successfully learned the reversed cues, and, contrary to our expectations, we found no evidence that Heliconius performed better than the other Heliconiini species. These results are surprising, given previous evidence linking the mushroom bodies to reversal learning in other insects, and the enhanced performance of Heliconius in other cognitive tests. This serves as a reminder that the functional consequences of brain expansion can be multifaceted, and do not necessarily result in an overall increase in general cognitive ability, but rather enhanced performance in specific, ecologically-relevant tasks.

animal behavior and cognition↗

bioRxiv2022

Rapid expansion and visual specialization of learning and memory centers in Heliconiini butterflies

How do neural systems evolve to support new behaviors? Changes in the abundance and diversity of neural cell types, and their connectivity, shape brain composition and provide the substrate for behavioral variation. We describe a striking example of neural elaboration in an ecologically diverse tribe of Heliconiini butterflies. By building extensive new datasets of neural traits across the tribe, we identify major bursts in the size and cellular composition of the mushroom bodies, central brain structures essential for learning and memory. These expansion events are associated with increased innervation form visual centers and coincide with enhanced performance in multiple cognitive assays. This suite of neural and cognitive changes is likely tied to the emergence of derived foraging behaviors, facilitated by localized specialization of neural networks. One-Sentence SummaryMajor shifts in brain composition and behavior in butterflies with unique foraging and dietary behaviors.

evolutionary biology↗