The stakes of this question are enormous. Insects are the most species-rich group of animals on Earth, with more than one million formally described living species, and the origin of powered flight in insects stands among the most transformative events in the history of terrestrial life. Wings opened up the air as a habitat, transformed pollination and predation, and set the stage for the staggering diversity that followed. Yet the relationships among the three major pterygote lineages, Ephemeroptera (mayflies), Odonata (dragonflies and damselflies), and Neoptera (insects capable of folding their wings back over their bodies), remained stubbornly unresolved, with competing hypotheses each backed by different bodies of evidence.

Three rival scenarios defined the debate. The Palaeoptera hypothesis holds that mayflies and odonates share a common ancestor, forming a clade called Palaeoptera that is the sister group of all other winged insects. The Chiastomyaria hypothesis instead pairs dragonflies with a grouping of mayflies and neopterans. The Metapterygota hypothesis takes the opposite arrangement, pairing mayflies with neopterans and leaving dragonflies on the earliest branch. Because these topologies imply very different histories for how wings were structured, how they moved, and how insect flight first evolved, resolving them has been a central challenge in reconstructing the insect tree of life.

The new study attacked the problem with an unusually comprehensive dataset. The researchers sequenced 16 new genomes from Chinese mayflies, a lineage that had been chronically undersampled in previous phylogenomic work, and integrated genomic and transcriptomic data from more than 100 insect species overall. This effort substantially closed the gaps in both taxon sampling and gene sampling that had plagued earlier analyses. The team then constructed two large amino-acid supermatrices built from universal single-copy orthologous nuclear genes, ensuring that the comparisons were based on genes present in exactly one copy across the sampled species and therefore less likely to mislead through ancient duplications.

What distinguishes the study is the systematic rigor applied to the analysis. Rather than relying on a single method, the researchers examined phylogenetic signals using both concatenation approaches, which pool all genes into one matrix, and multispecies coalescent methods, which model how individual gene trees relate to the underlying species tree. They deployed multiple evolutionary models, performed formal topological tests, dissected signals at the level of individual sites in the alignments, and ran simulation analyses to check whether their methods could recover the true tree under known sources of error. Across all of these diverse frameworks, the results consistently supported the monophyly of Palaeoptera: mayflies and odonates are sister groups, together forming the sister clade of Neoptera.

That consistency matters because the study also explains why the problem had resisted resolution for so long. During the rapid early radiation of winged insects, the researchers found that a combination of incomplete lineage sorting, in which ancestral genetic polymorphisms are randomly partitioned among descendant lineages, and gene tree estimation error affected approximately 40 percent of the gene trees in their dataset. This produced widespread topological discordance between individual gene trees and the true species tree. Different analytical frameworks handled this noise differently, which is precisely why earlier phylogenomic studies reached competing conclusions. By quantifying the scale of the problem and applying methods robust to it, the team was able to cut through the conflicting signals.

The resolution of the tree carries a profound implication for how we understand the origin of insect flight. Because mayflies and dragonflies, which cannot fold their wings flat over their bodies, form a group that is sister to the foldable-winged Neoptera, the non-foldable wings of Palaeoptera and the foldable wings of Neoptera are both novel traits that were independently acquired from an ancestral winged insect. In other words, the wing-folding mechanism of neopterans was not the retention of a primitive condition lost by mayflies and dragonflies; it was a later innovation. The ancestral winged insect already had wings, but neither the rigid flight apparatus of modern palaeopterans nor the folding hinge of modern neopterans.

To place these branching events in time, the researchers used molecular-clock analyses calibrated with 13 carefully selected fossil reference points. The results indicate that crown-group Pterygota, the lineage containing all living winged insects and their most recent common ancestor, originated in the Early Devonian, while crown-group Palaeoptera arose later, in the Late Devonian. Crucially, the analysis supports the conclusion that insect wings evolved only once. The subsequent history of the group was one of divergence and independent refinement of two very different flight architectures rather than repeated origins of flight itself.

The functional consequences of those two architectures shaped everything that followed. In neopterans, the wing-folding mechanism is enabled by rotation of the independent third axillary sclerite, a small skeletal element at the wing base that allows the hindwings to be tucked back over the abdomen. This seemingly modest anatomical feature provided the morphological and ecological foundations for the explosive radiation of Neoptera after the Carboniferous, since insects that could fold their wings could crawl through vegetation, burrow, and exploit microhabitats closed to insects with permanently outstretched wings. Mayflies and dragonflies, by contrast, evolved highly specialized rigid wing-base complexes adapted for gliding or high-speed predatory flight, trading the flexibility of folding for performance in the air.

The reconstructed evolutionary scenario shows that after the initial divergence of winged insects, Palaeoptera and Neoptera rapidly split and evolved their distinct wing structures in parallel: Neoptera developing its unique wing-folding apparatus, and Palaeoptera developing rigid wing bases for high-performance direct flight. Together, these innovations shaped the flight biomechanics and the species diversity of winged insects observed in nature today. The study was funded by the National Key R&D Program of China, the National Natural Science Foundation of China, and the China Postdoctoral Science Foundation. By uniting dense genome sampling, rigorous phylogenetic testing, and fossil-calibrated dating, the work demonstrates how a question posed in the nineteenth century can finally be answered with the tools of the twenty-first, and it offers a template for resolving other deep branches in the tree of life where rapid ancient radiations have scattered contradictory signals across the genomes of living species.

Subject of Research: Phylogenomic resolution of early winged insect evolution and the Palaeoptera Problem

Article Title: Genomic and fossil evidence sheds new light on the early evolution of winged insects

Article References: Genomic and fossil evidence sheds new light on the early evolution of winged insects. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: phylogenomics, Palaeoptera, insect evolution, mayflies, dragonflies, Neoptera, insect wings, molecular clock, Devonian, incomplete lineage sorting, fossils, PNAS

The investigation was led by Márcio Galvão Pavan of the Oswaldo Cruz Institute (Fiocruz) in Rio de Janeiro, together with Rodrigo Gurgel-Gonçalves of the University of Brasília and colleagues, including Fernando Abad-Franch and Fernando Araujo Monteiro, who contributed equally to the work. The team set out to answer a deceptively simple question: when light-colored bugs turn up inside carnaúba palms, are they R. nasutus, the species whose primary habitat these palms represent in northeastern Brazil, or could they actually be R. neglectus wearing, in effect, a different species’ colors? The answer, according to the combined genetic and morphological evidence, is frequently the latter.

The study’s foundation lies in an ecological and biogeographical puzzle. Rhodnius nasutus is typical of the Caatinga, Brazil’s seasonally dry, thorny scrubland biome, where it dwells chiefly in the crowns of Copernicia prunifera palms and is characteristically light brown in color. Rhodnius neglectus, by contrast, is a core-Cerrado species associated with Mauritia flexuosa palms and typically shows a much darker brown body. Because the Caatinga and Cerrado intergrade across a broad transition zone, the two palm species, and the bugs that inhabit them, occasionally come into geographic contact. That overlap set the stage for the color confusion the researchers document.

To untangle the situation, the team sampled triatomines from C. prunifera palms across the semiarid Caatinga and the Caatinga-Cerrado transition, comparing them with specimens collected from core-Cerrado M. flexuosa palms. Every insect was first identified by phenotype, meaning its visible color pattern and morphology. The researchers then turned to genetics, sequencing clones of the mitochondrial cytochrome b gene, a standard barcoding marker, and the nuclear ribosomal DNA internal transcribed spacer 2, or ITS2. This two-marker strategy allowed the team to compare signals from the maternally inherited mitochondrial genome with those from the nuclear genome, a contrast that proved decisive.

The morphological results were clear at the extremes but murky in the middle. Adult specimens from core-Cerrado Mauritia palms consistently displayed the dark brown coloration typical of R. neglectus, while adults from core-Caatinga localities showed the light brown hue typical of R. nasutus. But in bugs captured in carnaúba palms from the Caatinga-Cerrado transition zone and parts of the central-western Caatinga, color patterns were dubious, matching neither type reliably. Specimens that looked like typical light brown R. nasutus could not confidently be assigned on appearance alone, raising the possibility that field identifications based on color might have been systematically wrong in exactly these regions.

Genetics began to resolve the ambiguity. Bayesian genealogies built from cytochrome b sequences placed the dubious-phenotype specimens that resembled typical R. nasutus in a sub-clade that is sister to typical R. neglectus from Mauritia flexuosa palms, with roughly 2% mean cytb divergence separating the two sub-clades. In other words, the bugs that looked like R. nasutus carried mitochondrial genomes pointing to R. neglectus ancestry. This mitochondrial signal effectively dissolved the taxonomic uncertainty created by the shared coloration, demonstrating that insects occupying carnaúba palms in the transition zone belong, at least by maternal lineage, with R. neglectus.

The nuclear ITS2 marker told a less tidy story. ITS2 genealogies recovered both R. neglectus and R. nasutus as paraphyletic, meaning individuals of each nominal species were scattered across the gene tree rather than clustering neatly by species. Such patterns often arise when recently diverged species still share ancestral genetic variation. When the researchers applied a multispecies-coalescent analysis, a statistical framework designed to account for this shared ancestry, the dubious-phenotype bugs from C. prunifera clustered with typical R. neglectus. The analysis suggested that the messy ITS2 picture reflects incomplete lineage sorting, the retention of ancestral polymorphisms, rather than hybridization or misassigned species limits. The mito-nuclear discordance observed in the study is thus itself scientifically informative, illustrating how different genomes can carry different historical signals during the early stages of species divergence.

Why would two species converge on the same color? The authors propose that predator-driven natural selection is the most plausible mechanism. Triatomine bugs live in palm crowns where the substrate color is set by the palm’s dried leaf bases and fibers. In the core Cerrado, dark Mauritia crowns favor dark R. neglectus; in the core Caatinga, the lighter carnaúba substrate favors pale R. nasutus. But when R. neglectus colonizes carnaúba palms, individuals whose coloration better matches the light palm-crown substrate presumably enjoy better camouflage against visual predators such as birds and lizards. Over time, this selection pressure could produce R. neglectus populations whose light brown bodies are nearly indistinguishable from typical R. nasutus. This is a textbook scenario of adaptive phenotypic convergence, conceptually related to classic camouflage and mimicry systems in evolutionary biology, but documented here in disease vectors, where species identity has public health consequences.

The practical implications are significant. Chagas disease remains a major neglected tropical disease in Latin America, and surveillance programs depend on correctly identifying which vector species are present in a given area, because species differ in habitat preferences, domestic invasion behavior, and epidemiological relevance. If R. neglectus can masquerade as R. nasutus, field records based on color alone may misattribute vectors to the wrong species and thereby misguide control strategies. The study’s findings, the authors argue, call into question the widespread use of overall body color as a key phenotypic character in triatomine taxonomy. As molecular tools become more accessible, integrating DNA-based confirmation into routine vector surveillance may be essential wherever palm-dwelling Rhodnius species co-occur or share similar microhabitats.

Beyond the immediate applied concerns, the work contributes to a broader understanding of how color variation evolves in triatomines and how convergence can erode the morphological signals taxonomists depend on. The researchers received support from Brazil’s CAPES and CNPq funding agencies, and sampling was conducted under permit from the country’s biodiversity authority, ICMBio. By combining careful field collection across two biomes with mitochondrial and nuclear sequence analysis and modern coalescent modeling, the team has shown that even a character as apparently straightforward as body color can be shaped powerfully by ecology, and that species identities written in DNA may diverge sharply from those written on the insect’s back. For the bugs of the carnaúba palms, looking like the neighbor may be good for survival, but it makes life considerably harder for the scientists trying to tell them apart.

Subject of Research: Phenotypic convergence in the Chagas disease vector bugs Rhodnius neglectus and Rhodnius nasutus inhabiting Copernicia prunifera palms in Brazil

Article Title: Phenotypic convergence in Chagas disease vectors: Rhodnius neglectus from Copernicia prunifera palms may express the typical Rhodnius nasutus color phenotype

Article References: Pavan, M. G., Gurgel-Gonçalves, R., Corrêa-Antônio, J., Morelli, K. A., Bahia, A. C., Abad-Franch, F., & Monteiro, F. A. (2026). Phenotypic convergence in Chagas disease vectors: Rhodnius neglectus from Copernicia prunifera palms may express the typical Rhodnius nasutus color phenotype. Parasites & Vectors. https://doi.org/10.1186/s13071-026-07651-3

Image Credits: AI Generated

DOI: 10.1186/s13071-026-07651-3

Keywords: Triatominae, Rhodnius, Chagas disease, phenotypic convergence, convergent evolution, camouflage, Copernicia prunifera, cytochrome b, ITS2, incomplete lineage sorting, mito-nuclear discordance, Brazil