Biology subjects

Montgomery, S. H.

Publications and source records attributed to Montgomery, S. H..

At least 19 recordsLinked to original sources

bioRxiv2026

Characterisation of cis-regulatory elements and genome wide enhancer prediction in Heliconiini butterflies

The large-scale annotation and spatiotemporal characterisation of cis-regulatory promoters and enhancers remain limited in many non-model organisms, largely due to fragmented availability of multiomic datasets across species and developmental conditions. Heliconius butterflies, which have been used to investigate wing development and patterning, have provided key insights into the genetic architecture underlying morphological diversification and adaptive pigmentation. Despite this, we are limited in what we understand of how cis-regulatory dynamics drive phenotypic wing patterning variation. Here, by re-analysing and re-evaluating available data, we present a comprehensive new description of a cis-regulatory atlas for Heliconius wing development by integrating chromatin accessibility dynamics (ATAC-seq) with histone modification profiling (H3K27ac, H3K4me3). High-confidence peak sets enabled robust annotation of promoters and enhancers, revealing regulatory distributions consistent with canonical regulatory organisation. Promoters displayed comparatively higher conservation of transcription factor motifs, whilst enhancers exhibited greater sequence diversity, broader genomic distributions and more variable motif repertoires. Comparative analysis revealed cis-regulatory divergence to be primarily temporal, with substantial chromatin remodelling and differential histone enrichment across development, while regulatory dynamics were highly conserved between forewing and hindwing tissues. Extending these experimentally characterised regulatory landscapes, a convolutional neural network was trained for sequence-based enhancer prediction, achieving test AUROC and AUPRC values of 0.909 and 0.913, respectively. Predictions across 34 Heliconiini assemblies displayed significant enrichment within independently characterised accessible chromatin and conserved non-exonic elements (CNEEs), supporting their putative regulatory function. Overall, this study provides a large-scale characterisation of cis-regulatory dynamics and extends enhancer annotation across Heliconiini, providing a foundation for comparative investigations of regulatory conservation and diversification.

genomics↗

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

Ancient Rapid Radiation Underlies Persistent Phylogenomic Conflict in Early Collembola Diversification

Collembola (springtails) are among the most abundant and ecologically important soil arthropods, representing one of the oldest extant terrestrial hexapod lineages, with a fossil record extending to the early Devonian. Despite their relevance, phylogenetic relationships among the four extant orders (Entomobryomorpha, Poduromorpha, Symphypleona, and Neelipleona) have remained unresolved for over two decades. Here, we present the most comprehensive phylogenomic analysis of Collembola to date, comprising 1,127 single-copy orthologues from 145 taxa representing 19 families. To improve orthology inference, we developed a novel HMM-based filtering pipeline that significantly reduced hidden paralogy in BUSCO-derived datasets. Across multiple dataset configurations, gene-jackknife replicates, and various maximum-likelihood analyses, we consistently recovered Poduromorpha as the earliest-diverging lineage. Coalescent-based methods instead highlighted discordant arrangements characterised by extremely short internal branches and low quartet support, a pattern consistent with pervasive incomplete lineage sorting and reticulate evolutionary history. We further dissected the phylogenetic signal by exhaustively evaluating all possible inter-order topological arrangements, both on the full concatenated dataset and gene-by-gene, to identify the most phylogenetically informative loci. These analyses rejected the great majority of previously proposed hypotheses, narrowing support to only two statistically indistinguishable topologies (T11 and T4), with the Poduromorpha-first arrangement consistently favoured across both site-homogeneous and site-heterogeneous substitution models. Finally, with molecular dating, we estimated the origin of crown Collembola in the Early Devonian, with the diversification of the extant orders in the Carboniferous. Several extant genera were estimated to be older than many currently recognized families, highlighting the exceptional evolutionary persistence of springtail lineages and suggesting that lineage longevity should be considered when interpreting higher-level taxonomic diversity.

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↗

bioRxiv2026

Genomic insights into bacterial isolates dominating honeypot ant crop microbiomes reveal metabolically distinct Fructilactobacillus sp.

Honeypot ants engage in a convergently-evolved phenotype called repletism, where specialized workers expand their crops and gasters to store vast amounts of food internally. They then store that food for months to support colonies during times of food scarcity. This fascinating phenotype is not well-understood and very little is known about the microbial interactions happening within the fructose-rich replete crop. Previous research using amplicon sequencing showed that Fructilactobacillus makes up nearly 100% of the crop microbiomes of Myrmecocystus mexicanus repletes. This striking result and successful isolation of those strains led to the present investigation into the phylogenetic diversity of these strains and any clues to the nature of the symbiotic relationship between them and the ant host. We find that the isolates from these repletes represented two evolutionary lineages, both most closely related to F. fructivorans. One of those lineages was also found to be phylogenetically and metabolically distinct from all other Fructilactobacillus reference genomes used in this study. This discovery in a genus of bacteria that are highly relevant for fermented human foods and will also lay the groundwork for future understanding of the convergent evolutionary mechanisms of repletism in ants. 3. Impact statementThese analyses add to the literature by identifying a new microbe within a genus that is relevant to food systems. In addition, the host phenotype is convergently evolved and likely microbe-mediated (or at least highly exposed). Understanding this system allows for the testing of ideas of coevolutionary hypotheses with natural replicates. We expect interest to come from food safety and probiotics researchers, evolutionary biologists that think about the impacts of microbes, microbial ecologists interested in novel systems, and those interested in bacteria that may display unique metabolic possibilities. This output allows for the clear future examination of this system with many clear hypotheses. Our analysis allows for the creation of a new and unique model system of host-microbe symbiosis. 4. Data summaryNew genomes assembled in this work can be found under BioProject ID PRJNA1449409. https://www.ncbi.nlm.nih.gov/bioproject/?term=PRJNA1449409. Reference bacterial genomes were obtained from NCBI at the following accession numbers: SAMN20557570, SAMN28081009, SAMN28081010, SAMN02597458, SAMN43111088, SAMN28081011, SAMN28535231, SAMN04505734, SAMN28081013, SAMN33452149, SAMN37926504, SAMN02849426, SAMN02470196, SAMN02369432, SAMN02797779, SAMN02797782, SAMN02797768, SAMN09762388, SAMN12785275, SAMEA117660288. The honeypot ant genome was obtained from SAMN37666067. Raw proteomics files will be uploaded to ProteomeXchange with a unique identifier upon manuscript acceptance.

genomics↗

bioRxiv2026

Genetic architecture of cichlid brain morphology

How evolutionary and developmental processes interact to determine axes of neural variation that produce behavioural diversity has been debated for many decades, with alternative hypotheses giving differential emphasis to functional coupling, which favours co-evolution, and developmental constraint, which enforces it. A critical omission is data on the genetic architecture of brain size and structure, which more closely illuminates the shared developmental dependencies between components of an integrated system. Here, we exploit ecological divergence between Astatotilapia calliptera and Aulonocara stuartgranti, two closely related cichlid species from Lake Malawi, to explore the genetic architecture of brain evolution. Using computer vision and machine learning techniques to extract volumetric data from micro-tomographic images, we first demonstrate significant divergence in brain composition between these species. Genomic and micro-tomographic imaging data from a population of hybrids generated between the two species were used to investigate genetic factors shaping this differentiation. We show that the majority of brain components are integrated phenotypically in hybrids, but genetic correlations between them are generally weaker. We further show that variation in multiple brain components is associated with variation in largely structure-specific quantitative trait loci, rather than determined by genetic factors with broad effects across the entire brain. These results suggest a genetic architecture that can facilitate modular changes in brain structure, and imply that individual components are independently evolvable.

evolutionary biology↗

bioRxiv2026

Cognitive robustness in a new insect model of extended longevity

Human life expectancy has jumped by several decades in the last century, but the healthspan has not followed suit. The ageing population has come with an increased prevalence of neurodegenerative disease, and insects have proven to be valuable models of these conditions and their associated cognitive decline. The Heliconius butterfly genus is an emerging system in insect cognition, having recently evolved a significant expansion in neural centres of learning and memory, alongside enhanced stability of visual long-term memory in comparison with their close relatives in the Heliconiini tribe. This is linked to the cognitive demands imposed by Heliconius spatially-faithful foraging behaviour for a protein-rich diet of pollen, and co-occurs with a dramatic lifespan extension in this genus over the other Heliconiini outgroups. Here, we investigate whether the Heliconius cognitive healthspan is similarly discrepant, or if any cognitive decline is instead delayed in accordance with their lifespan extension. We first report evidence that investment in learning and memory circuits co-evolves with Heliconiini lifespan. We then conduct learning and memory assays across the lifespans of a representative longer-lived Heliconius, H. hecale, and the shorter-lived Heliconiini outgroup, Dryas iulia. Across both species, and particularly in H. hecale, we find evidence for cognitive robustness in late life, in contrast to evidence for widespread cognitive declines in insects. Our results add a new taxonomic order to the study of age-related memory impairment, and suggest Heliconius as a valuable model system for mechanistic studies of the maintenance of neurological health in the context of extended life.

animal behavior and cognition↗

bioRxiv2025

fgf8a signalling shapes brain divergence between Malawi cichlids

Brain diversification is intimately linked with adaptive radiations, yet the underlying molecular basis remains poorly understood. Here, we examine the mechanisms of neural evolution in two ecologically divergent Lake Malawi cichlid species: a generalist, Astatotilapia calliptera, and a pelagic piscivore, Rhamphochromis sp. chilingali. We demonstrate that forebrain domains diverged independently from other brain regions in these species, consistent with mosaic brain evolution. We identify fibroblast growth factor 8a (fgf8a) as a key factor underlying this neuroanatomical divergence. Species-specific fgf8a expression patterns during critical developmental windows correlate with adult brain differences. Functional knockout experiments confirm fgf8as essential role in cichlid brain patterning, directly linking this conserved developmental gene to interspecific neuroanatomical variation. We identify species-specific transposable element repertoires in the Malawi cichlid fgf8a locus that function as developmental enhancers in brain and sensory systems, providing a potential mechanism for expression divergence between species. Phylogenetic analysis across the radiation reveals elevated transposable element polymorphism at the fgf8a locus in Rhamphochromis, suggesting ongoing regulatory evolution in this clade. Our findings reveal how conserved developmental programmes can accommodate regulatory modification, providing a mechanistic framework for understanding rapid neural diversification during adaptive radiation.

developmental biology↗

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↗

bioRxiv2025

Evolution of increased longevity and slowed ageing in a genus of tropical butterfly

Evolution has given rise to lifespans in extant species ranging from days to centuries. Given that mechanisms of ageing are highly conserved, studying long-lived lineages across the animal kingdom could yield insights relevant for healthy ageing in humans. However, typical models of extended lifespan often live for decades, making them impractical for longitudinal studies. Ideal model systems would be organisms that are naturally long-lived compared to their close relatives, but have lifespans on experimentally tractable scales. Here, we present the Neotropical butterfly genus Heliconius as a novel model system for the evolution of extended longevity. We collate data from 27 species across the Heliconiini tribe to reveal a 25-fold variation in lifespan within the group, with our 348-day maximum for Heliconius hewitsoni longer than any butterfly species previously recorded in the scientific literature. While previous work has attributed this lifespan extension to a plastic response to enhanced nutrition, we conduct detailed survival and functional senescence analyses on two species representative of shorter- and longer-lived clades to show evidence of evolved, heritable mechanisms of slowed ageing in Heliconius. Our results add a new case study to the canon of noteworthy agers, and provide valuable insights into the evolution of increased longevity.

evolutionary biology↗

bioRxiv2025

Conservation of sensory pathways implies a localised change in the mushroom bodies is associated with cognitive evolution in Heliconius butterflies

Acquisition of novel behaviour is reflected in changes in sensory investment or integration, but the exact nature of these changes is often unclear. Within the Neotropical butterfly tribe, Heliconiini, the genus Heliconius possess 4-fold larger mushroom bodies, an insect learning and memory centre, than closely related Heliconiini. Mushroom body expansion in Heliconius co-occurred with a dietary innovation, and is associated with systematic spatial foraging and extended lifespans. Heliconiini therefore offer an attractive system for studying how behavioural evolution is facilitated by changes in neural systems. Heliconius foraging relies on visual scene memories and, indeed, Heliconius have more stable visual long-term memory, and evidence of visual specialisation in the mushroom bodies. Here, we explore how vision-specific neuroanatomical and behavioural enhancement in Heliconius impacts sensory pathways upstream of the mushroom bodies by assessing investment across the eyes, sensory structures and projection pathways. Despite evidence of refinement in visually-based behaviour, we found no increased investment in visual structures, brain areas or pathways. This suggests that the rapid expansion of the Heliconius mushroom body occurred in a context of conserved detection and processing of visual cues, and that a localised shift within integrative brain centres facilitated the evolution of Heliconius novel behaviours.

evolutionary biology↗

bioRxiv2025

Gene loss associated with plasticity-first evolution in Heliconius butterflies

Phenotypic plasticity occurs when a genotype can produce more than one phenotype under different environmental conditions. Genetic accommodation allows plastic phenotypes to be tuned to new environments and eventually to even be lost. The colourful and toxic Heliconiini butterflies have biochemical plasticity - they either sequester their cyanogenic glucosides (CG) from their larval hostplant or biosynthesize them when compounds for sequestration are not available. Here, we trace the evolution of CG biosynthesis in Heliconiini butterflies, a fundamental component of this biochemical plasticity. We first reconstructed the evolutionary history of biochemical plasticity in Heliconiini butterflies using chemical data from over 700 individuals, demonstrating that plasticity was ancestral in the tribe and further lost in a few clades, such as the Sapho clade that only sequester CGs. In lepidopterans, CG biosynthesis has been fully characterized in the moth Zygaena filipendulae, and is composed of CYP405A2, CYP332A3, and UGT33A1. Thus, we CRISPR-edited the gene CYP405 in Heliconius erato, and confirmed that CYP405-knockout caterpillars do not biosynthesize CGs. We identified the CYP405s and CYP332s in other lepidopterans and found that both genes were independently co-opted into CG biosynthesis in the Heliconiinae butterflies and Zygaena moths. Most lepidopterans have a CYP332, but CYP405 is mostly restricted to butterflies and has been duplicated in all Heliconius species. Although several CYP405 copies were found in the Sapho clade, they lack structurally important P450 domains, which explain they loss of biochemical plasticity via specialization in CG sequestration. Our findings represent one of the few examples of plasticity-first evolution in which the genetic mechanisms associated with its accommodation/assimilation are known.

evolutionary biology↗

bioRxiv2025

Distinct evolutionary trajectories of two integration centres, the central complex and mushroom bodies, across Heliconiini butterflies

Neural circuits have evolved to produce cognitive processes that facilitate a species variable behavioural repertoire. Underlying this variation are evolutionary forces, such as selection, that operate on changes to circuitry against a background of constraints. The interplay between selection and potentially limiting constraints determine how circuits evolve. Understanding how this process operates requires an evolutionary framework that facilitates comparative analysis of neural traits, within a clear behavioural and functional context. We leverage a large radiation of Heliconiini butterflies to examine how selection shapes the evolution of the central complex and the mushroom bodies, two integration centres in the insect brain involved in spatial navigation. Within the Heliconiini, one genus, Heliconius, performs systematic spatial foraging and navigation to exploit specific plants as a source of pollen, a novel dietary resource. Closely related genera within Heliconiini lack this dietary adaptation, and are more vagrant foragers. The evolution of increased spatial fidelity in Heliconius has led to changes in brain morphology, and in specific learning and memory profiles, over a relatively short evolutionary time scale. Here, using a dataset of 41 species, we show that in contrast to a massive expansion of the mushroom bodies, the central complex and associated visual processing areas are strongly conserved in size and general architecture. We corroborate this by characterising patterns of fine anatomical conservation, including conserved patterns in dopamine and serotonin expression. However, we also identify a divergence in the expression of a neuropeptide, Allatostatin A, in the noduli, and in the numbers of GABA-ergic ellipsoid body ring neurons and their branching in the fan-shaped body, which are essential members of the anterior compass pathway. These differences match expectations of where evolutionary adaptability might occur inside the central complex network and provide rare examples of divergence of these circuits in a shallow phylogenetic context. We conclude that due to the contrasting volumetric conservation of the central complex and the massive volumetric differences in the mushroom bodies, their circuit logics must determine distinct responses to selection associated with divergent foraging behaviours.

neuroscience↗

bioRxiv2025

Evolution of the olfactory system during the radiation of Heliconiini butterflies

Sensory system evolution plays a crucial role in shaping species interactions with their environment, yet the extent to which olfactory system diversity reflects ecological and evolutionary pressures at a macroevolutionary scale remains unclear. Here, we investigate the evolution of the olfactory system across the Heliconiini butterfly tribe, an ecologically diverse but closely related group. Using a comparative approach, we examined variation in antennal lobe morphology and its constituent structures, the glomeruli and antennal lobe hub, as well as olfactory receptor repertoires across species. We found that antennal lobe size variation is driven by independent shifts in glomerular and antennal lobe hub volumes, with species-specific differences occurring against a backdrop of broader phylogenetic stability. While no direct associations with ecological traits were observed, certain species showed large expansions in total glomerular volume and olfactory receptor numbers, warranting further investigation into unmeasured ecological or behavioural factors. Additionally, comparisons between wild-caught and insectary-reared individuals revealed a surprising pattern of developmental plasticity, with antennal lobe hub volumes increasing and glomeruli volumes decreasing in captivity, highlighting the influence of environmental conditions on neural development. These findings suggest that olfactory evolution in Heliconiini is shaped by both evolutionary divergence and developmental plasticity, emphasizing the need to integrate phylogenetic, ecological, and developmental perspectives to fully understand sensory system adaptation.

evolutionary biology↗

bioRxiv2025

Convergent molecular evolution associated with repeated transition to gregarious larval behaviour in Heliconiini

Collective behaviour forms the basis for many anti-predator strategies. Within Lepidoptera, larval gregariousness has evolved convergently across many phylogenetically disparate lineages. While the selection pressures shaping variation in larval social behaviours are well investigated, much less is known about the mechanisms that control social attraction and behavioural coordination. Similarly, little is known about how secondary selection pressures associated with social living shape genome evolution. Here, using genomic data for over 60 species from an adaptive radiation of Neotropical butterflies, the Heliconiini, in which gregarious behaviour has evolved repeatedly, we explore the molecular basis of repeated convergent shifts towards gregarious larvae. We focus on three main areas of genomic evolution: differential selection on homologous genes, accelerated rates of evolution on non-coding regions of key genes, and differential gene expression in the brains of solitary and gregarious larvae. We identify strong signatures of convergent molecular evolution, on both coding and non-coding loci, in Heliconiini lineages which evolved gregarious behaviour. Molecular convergence is also detected at the transcriptomic level in larval brains, suggesting convergent shifts in gene regulation in neural tissue. Among loci showing strong signals of convergent evolution in gregarious lineages, we identify several strong candidates linked to neural activity, feeding behaviour, and immune pathways. Our results suggest sociality profoundly changes the selection pressures acting on multiple physiological, immunological and behavioural traits.

evolutionary biology↗

bioRxiv2024

Ancestral complexity and constrained diversification of the ant olfactory system

Ants are a monophyletic but diverse group of social insects whose heightened olfactory ability has been crucial to their evolutionary success. Their complex olfactory system is believed to have evolved due to the expansion of a specialized olfactory subsystem and the associated clade of olfactory receptors. Specifically, ants exhibit specialized antennal hairs known as basiconic sensilla, whose neurons project to a distinctive cluster of numerous, small glomeruli in their antennal lobes. This adaptation is believed to be linked to their social lifestyle, enabling the detection of recognition cues like cuticular hydrocarbons (CHCs), which are essential for nestmate recognition and maintaining colony cohesion. However, our understanding of the ant olfactory system remains incomplete, lacking evolutionary context and phylogenetic breadth, which leaves the complexity in their most recent common ancestor uncertain. We thus conducted a comparative study of neuroanatomical traits across the phylogeny of the Formicidae. Our findings reveal a common blueprint for the ant olfactory pathway, alongside lineage-specific adaptations. This highlights a dynamic evolution, particularly for the CHC-related subsystem. Ancestral trait reconstructions indicate that olfactory sophistication predates the most recent common ancestor of ants. Additionally, we found that the chemical complexity of species-specific recognition cues is associated with neuronal investment within the olfactory system. Lastly, behavioral experiments on anatomically divergent ant species show that, despite variation in neuroanatomical traits, ants consistently discriminate nestmates from non-nestmates. This suggests that the evolution of ants olfactory system integrates sensory adaptations to diverse chemical environments, facilitating communication, a key to social behaviors.

evolutionary biology↗

bioRxiv2024

Modality specific memory enhancement in Heliconius butterflies

How animals perceive, process and respond to environmental cues is tightly tuned to the species-specific demands, and reflected by the structure of neural systems. In the Neotropical butterflies, Heliconius, the mushroom bodies, insect learning and memory centres, are significantly expanded compared to their closest relatives. This expansion coincided with the evolution of a novel diet, pollen feeding, and a spatial foraging behaviour consistent with trap-lining. Previous research has shown that Heliconius have more accurate visual long-term memory than other Heliconiini. Here, we tested whether this enhanced memory stability is specific to visual cues by conducting a long-term olfactory memory assay in two Heliconius species and two outgroup species. We found no differences in the long-term olfactory memory between Heliconius species and the outgroup species. Combining data from olfactory and visual memory trials confirms a significant shift in performance among sensory modalities between Heliconius and outgroup genera. In contrast, tests of how Heliconiini prioritise olfactory and visual cues when in presented in conflict also show no consistent shift in attentiveness to sensory cues between species. Our data provide a rare case where memory performance has been compared across species and sensory modalities, to identify evidence of a modality specific shift.

animal behavior and cognition↗

bioRxiv2024

Mutualisms within light microhabitats drive sensory convergence in a mimetic butterfly community

Niche partitioning within variable habitats can expose species to distinct sensory information. Vision is the primary sensory modality used by many animals to interact with their habitat. However, within diurnal terrestrial ecosystems, little is known if, and how, variation in light environments impact species assemblages and visual system evolution. By studying a diverse, sympatric community of mimetic butterflies, we demonstrate that forest architecture creates a mosaic of light microhabitats that drive adaptive sensory convergence and divergence in both peripheral and central sensory systems. Our study provides insights into the dynamic response of visual systems when confronted with similar ecological challenges, and illustrates the wide-reaching consequences of interspecific mutualisms, such as mimicry, on organismal evolution.

evolutionary biology↗