Biology subjects

Manel, A. N.

Publications and source records attributed to Manel, A. N..

4 recordsLinked to original sources

bioRxiv2026

A hawkmoth's point of view - Innate symmetry preferences are informed by floral display and foraging function in an insect pollinator

Floral visual cues are key for flower recognition and feeding in many pollinators. In insects, innate preferences for characteristic floral colour and pattern cues can guide naive foragers during their initial foraging. Symmetry is suggested to be one such foraging cue, since it is a remarkably conserved floral feature, with flowers mainly displaying radial or bilateral morphologies. Insect pollinators like honeybees, bumblebees, and hoverflies have been found to distinguish symmetry from asymmetry spontaneously or through learning. However, whether innate preferences for floral symmetry types, i.e. radial or bilateral, influence naive flower choice, and whether such preferences are linked to functional benefits during foraging remains uncertain.We investigated innate symmetry choice and its associated foraging function in the hummingbird hawkmoth (Macroglossum stellatarum). Besides relying on pattern cues for flower choice, these hawkmoths feed while hovering, making symmetry a valuable visual cue for flight and proboscis control. In choice assays, the hawkmoths' innate preferences for symmetry types depended on the floral display planes, with considerable differences between the horizontal and vertical displays. Tracking the hawkmoths during foraging revealed that in both display planes, the innately preferred patterns increased foraging success by guiding approach and nectary search. While an analysis of flowers visited by hawkmoths in nature did not reveal the same link between symmetry and display plane, a majority of plant species with vertically displayed flowers showed features matching those innately preferred by the hawkmoths. In this study, we provide the first instance of display-dependent innate foraging preferences and highlight how visuomotor strategies in nectivorous insects may have coevolved with flower features.

animal behavior and cognition↗

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↗

bioRxiv2025

Hawkmoths learn best without negative reinforcement in a differential colour association task

Visual learning in insects can be strongly influenced by the underlying context and conditions. Improved colour learning has been demonstrated with differential conditioning using reward-aversion paradigms in eusocial insects like wasps, bumblebees, and honeybees, where substances that induce strong aversion, such as quinine, enable more accurate learning. Although the associations created during learning are intrinsically linked to the reinforcements used, few studies have compared the role of negative reinforcements in shaping these associations, and their relevance across insect groups with different life histories. In our study, we compared the effects of aversive substances for learning in the hummingbird hawkmoth (Macroglossum stellatarum), a solitary pollinator that relies on vision for foraging. Linking to previous learning studies in insects, we combined a sugar-rewarded target with a distractor that was paired with either quinine, salt, citric acid, water, or was presented with no aversive substance. Learning was assessed by conditioning hawkmoths to invert a strong colour preference between perceptually close or distant colour pairs, to provide tasks with disparate challenges. Contrary to results from eusocial insect species, hawkmoths trained with quinine were worse at switching preferences between similar colours compared to training with citric acid or appetitive-only differential conditioning. Learning success was associated with the animals foraging plasticity, where negative reinforcements were found to suppress exploration during foraging. Furthermore, we show that quinine interfered with sucrose perception, potentially impairing target acquisition during conditioning. Our results provide insights into the impact of negative reinforcements on solitary foragers and highlight the role of sensory ecology and life history in shaping learning outcomes.

animal behavior and cognition↗

bioRxiv2023

Quantifying visual acuity in Heliconius butterflies

Heliconius butterflies are well-known for their colourful wing patterns, which advertise distastefulness to potential predators and are used during mate choice. However, the relative importance of different aspects of these signals will depend on the visual abilities of Heliconius and their predators. Previous studies have investigated colour sensitivity and neural anatomy, but visual acuity (the ability to perceive detail) has not been studied in these butterflies. Here, we provide the first estimate of visual acuity in Heliconius: from a behavioural optomotor assay, we found that mean visual acuity = 0.49 cycles-per-degree (cpd), with higher acuity in males than females. We also estimated visual acuity from eye morphology and reported slightly lower values (mean visual acuity = 0.38 cpd), but acuity was still higher in males. Finally, we estimated how visual acuity affects Heliconius visual perception compared to a potential avian predator. Whereas the bird predator maintained high resolving power, Heliconius lost the ability to resolve detail at greater distances, though colours may remain salient. These results will inform future studies of Heliconius wing pattern evolution, as well as other aspects in these highly visual butterflies, which have emerged as an important system in studies of adaptation and speciation.

evolutionary biology↗