Biology subjects

Borrero, J.

Publications and source records attributed to Borrero, J..

5 recordsLinked to original sources

bioRxiv2026

Adaptation in the eye and brain contributes to species divergence in visual perception in Heliconius butterflies

Sensory systems mediate the interaction between organisms and their environment, but how complex sensory pathways evolve and relate to variation in perception and behavior across ecological contexts, remains poorly understood, especially for terrestrial taxa. Here, we investigate whole-visual-system adaptation in Heliconius erato butterflies. Using continent-wide sampling, we demonstrate that within H. erato, facet count significantly decreased with increasing elevation. Common-garden rearing of low-elevation H. erato populations from Ecuador and their high-elevation sister species, H. himera, showed that eye and brain morphology are heritable, and comparisons to genomic measures of divergence indicates that this variation is due to divergent selection. Parallel comparisons from Colombia involving H. chestertonii (high elevation) and H. erato venus (low elevation) further revealed that eye and brain morphology can evolve as independent, decoupled traits. For both locations, differences in visual acuity correlated with variation in facet count. We also observed parallel evolution of spectral sensitivity, with independent high-elevation populations having fewer red-reflecting lateral filtering pigments. To experimentally link visual system morphology to behavior, we assessed visual acuity in second-generation H. erato cyrbia-H. himera hybrids. Overall, acuity was influenced by facet count, and when analyzed together with brain morphology, by a positive interaction between facet count and optic lobe volume, demonstrating that structural investment in the eye and neural expansion combine to maximize visual perception. This work shows that visual adaptation is a multi-layered process whereby sensory traits can evolve independently under localized ecological pressures, but evolution across the visual pathway contributes to refinements in behavioral performance.

evolutionary biology↗

bioRxiv2026

Ecological divergence and post-eclosion brain development shape visual performance during Heliconius speciation

Sensory adaptation is increasingly recognized as a key driver of ecological speciation, but how visual system divergence is coordinated across development, and how this translates into behavioral differences, remains poorly understood. The butterfly Heliconius cydno, which inhabits closed-canopy forests, has larger eyes and greater investment in visual brain centers than its sympatric close-relative H. melpomene, which occupies more open forest-edge habitats, suggesting divergent ecological selection on the visual system. However, the behavioral consequences of these visual adaptations, their developmental trajectories, and whether they break down in hybrids is unknown. To address these questions, we combined ecological field data with behavioral assays and deep-learning-assisted segmentation of neuroanatomy. Visual acuity - the ability to resolve spatial detail - was higher in H. cydno, consistent with its greater ommatidia number, but also increased with age in both species despite no change in external eye morphology. These improvements coincided with the onset of male courtship and female oviposition, suggesting that early adult neurodevelopment shapes visual performance and may support the demands of reproduction. Brain morphology showed species-specific trajectories of post-eclosion optic lobe growth that broadly paralleled increases in acuity and were accompanied by ongoing neurogenesis in the adult optic lobes. While hybrids exhibited intermediate visual acuity, relationships among different components of the visual system were disrupted in hybrids. Together, these results show that ommatidia number alone cannot explain variation in visual acuity, and highlight how coordinated sensory evolution, and its breakdown in hybrids, may contribute to divergence during the early stages of speciation. Significance StatementAdaptation of sensory systems is increasingly recognized as a key driver of species formation, but it is unclear how these systems develop and shape behavioral differences. Using closely related Heliconius butterflies adapted to different light environments, we show that visual acuity improves during early adulthood through neural development, despite no change in eye structure. This maturation coincides with the onset of reproductive behaviors and is accompanied by growth and neurogenesis in visual brain regions. In hybrids, coordination among sensory traits breaks down, resulting in intermediate visual performance. These results show that sensory development is critical for behavioral adaptation and suggest that its integration contributes to the maintenance of species boundaries.

evolutionary biology↗

bioRxiv2025

Altitudin S from Bacillus altitudinis ECC22 defines a new subgroup of circular bacteriocins

Bacteriocins are ribosomally synthesized antimicrobial peptides exhibiting diverse structures and mechanisms of action. Bacillus altitudinis ECC22, previously shown to produce the circular bacteriocins pumilarin and altitudin A, was found to harbor an additional biosynthetic gene cluster encoding a novel circular bacteriocin, designated altitudin S Proteomic analysis of active supernatant fractions confirmed the production of altitudin S, with a molecular mass of 8379 Da, consistent with head-to-tail cyclization. The peptide is synthesized as a 132-residue precursor comprising a 56-amino-acid leader and a 76-residue circular mature core. Structural modeling predicted a compact saposin-like fold composed of five -helices and a strongly cationic surface (pI {approx} 11.0, net charge +13). Altitudin S was successfully produced using a cell-free protein synthesis system coupled to split-intein mediated ligation (IV-CFPS/SIML) and exhibited a narrow but reproducible antimicrobial spectrum. Comprehensive sequence, structural, and phylogenetic analyses revealed that altitudin S is a highly divergent circular bacteriocin, defined by distinctive sequence features and physicochemical properties, including an exceptionally high isoelectric point, net charge, and low hydrophobicity. Bioprospecting across sequence databases identified homologs of altitudin S in diverse Bacillales species, all showing high sequence similarity, conserved structural features and preservation of its distinctive physicochemical profile. Genomic analysis further revealed a conserved biosynthetic gene cluster among all altitudin S homologs, notably including a gene encoding a characteristic M48-family metallopeptidase. Altogether, these findings support the classification of altitudin S and its homologs as representatives of a novel subgroup of circular bacteriocins.

microbiology↗

bioRxiv2025

Sexual dimorphism in pollen foraging and sensory traits in Heliconius butterflies

Sexual dimorphism in foraging behaviour is widespread in insects and may arise from differences in nutritional demands, sensory systems, or cognition. Heliconius pollen-feeding is an evolutionary innovation among butterflies that supports extended lifespans and sustained reproduction. However, how foraging behaviour varies between the sexes and how it relates to sexually dimorphic traits remains poorly understood. We investigated sex-specific foraging strategies in wild Heliconius himera, a highland specialist from southern Ecuador, using field surveys and DNA metabarcoding. Females carried more pollen than males, consistent with higher nutritional demands, yet we observed no differences in plant richness and composition. This indicates that sex differences reflect effort in foraging behaviour rather than shifts in plant choice. Gut samples revealed greater pollen diversity and a more consistent community profile than proboscis samples, suggesting they better capture cumulative foraging history. We also quantified sexually dimorphic sensory traits and found that males had larger eyes and more ommatidia, whereas females had larger mushroom bodies. While the functional significance of these differences remains unclear, these patterns are consistent with sexual dimorphism reported across Heliconius and suggest males and females may be under divergent selective pressures. Our findings highlight how sex-specific foraging differences can arise from differential effort on shared floral resources and co-occur with divergent sensory and neural investment, offering insights into the ecological basis of intraspecific variation in pollen use.

animal behavior and cognition↗

bioRxiv2024

Sensory weighting reflects changing patterns of visual investment during ecological divergence in Heliconius butterflies.

Integrating information across sensory modalities enables animals to orchestrate a wide range of complex behaviours. The relative importance placed on one sensory modality over another reflects the reliability of cues in a particular environment and corresponding differences in neural investment. As populations diverge across environmental gradients, the reliability of sensory cues may shift, favouring divergence in neural investment and the weight given to different sensory modalities. During their divergence across closed-forest and forest-edge habitats, closely related butterflies Heliconius cydno and H. melpomene evolved distinct brain morphologies, with the former investing more in vision. Quantitative genetic analyses suggest selection drove these changes, but their behavioural effects remain uncertain. We hypothesised that divergent neural investment may alter sensory weighting. We trained individuals in an associative learning experiment using multimodal colour and odour cues. When positively rewarded stimuli were presented in conflict pairing positively trained colour with negatively trained odour, and vice-versa, H. cydno favoured visual cues more strongly than H. melpomene. Hence, differences in sensory weighting may evolve early during divergence and are predicted by patterns of neural investment. These findings, alongside other examples, imply that differences in sensory weighting stem from divergent investment as adaptations to local sensory environments.

evolutionary biology↗