The research team, led by biogeographers working with a time-calibrated phylogeny built from more than 2,500 ultraconserved elements and calibrated with Dominican amber fossils, estimated that the most recent common ancestor of the main kissing bug tribes arose around 59.2 million years ago. That date is older than many previous estimates, which had placed the origin of the subfamily between 45 and 30 million years ago, and it suggests that the initial diversification of Triatominae began significantly earlier than previously recognized, potentially preceding the major Andean uplift that reshaped the South American landscape.

To reconstruct where the group came from, the researchers fitted a dispersal-extinction-cladogenesis model to a presence-absence matrix of 96 species mapped across 11 bioregions derived from a network-based regionalization of the Americas. The model indicated that the ancestral range of the entire clade encompassed multiple areas, with northern South America and parts of Mesoamerica emerging as the most likely, albeit with small probability. This pattern points to a widespread or complex ancestral distribution rather than a single narrowly defined point of origin, though the classical hypothesis that the group arose in Central or northern South America remains the most plausible.

The team then simulated dispersal histories using 100 biogeographic stochastic mappings, generating 6,591 dispersal events whose timing could be compared across replicates. Because the number of branches in a phylogeny increases toward the present, raw event counts naturally rise as more lineages become available to disperse. To correct for this inherent bias, the researchers normalized dispersal frequency by the number of lineages through time, revealing a pattern that raw counts had obscured: a pronounced decline from roughly 60 to 35 million years ago, followed by a gradual recuperation toward the present.

A threshold regression model identified two significant breakpoints at 50 and 30 million years ago, delineating three phases with distinct linear trends. Phase A, spanning 60 to 50 million years ago, showed high normalized dispersal, with lineages moving from the Amazonian region toward northern South America and from northern South America into Mesoamerica, as well as from the Caatinga toward the Cerrado. Phase B, from 50 to 30 million years ago, exhibited a substantial decline and stabilization in dispersal activity, with movements concentrated among Mesoamerica and northern South America and routes reaching the Páramos, Caatinga, and Chaco. Phase C, from 30 million years ago to the present, marked a resurgence in dispersal with the most complex and frequent patterns of the entire reconstruction.

The association between these phases and climate is striking. Phase A coincided with the Paleocene-Eocene transition, a period of significant global warming that included the Paleocene-Eocene Thermal Maximum, and the higher dispersal rate during this interval may have been facilitated by warmer conditions that expanded habitat connectivity and suitability, particularly from tropical source regions like Amazonia. Phase B aligned with global cooling and the transition into the Oligocene, when temperatures dropped sharply. The researchers note that previous analyses of global plant range shifts revealed an approximately 30 percent decrease in movements into the world’s tropics during the Early Eocene Climatic Optimum around 52 million years ago, suggesting large-scale vegetational changes that could have influenced dispersal dynamics. Cooler temperatures might have reduced habitat suitability, increased environmental filtering, or restricted connectivity between regions, thereby limiting dispersal success for the kissing bug lineages.

Phase C encompasses the Miocene, Pliocene, and Pleistocene, a period of fluctuating but generally recovering temperatures compared to the Oligocene minimum, leading into the Quaternary glacial cycles. During this phase, a high frequency of bidirectional dispersals was observed between Mesoamerica and the Nearctic region, likely facilitated by the formation and stabilization of the Isthmus of Panama. Routes from Amazonia extended toward the Páramos and the Caatinga, indicating the continued influence of Amazonia as a source or transit area. Within the Atlantic biomes, a dynamic and reciprocal exchange between the Caatinga and the Atlantic Forest was evident, and dispersal routes following the South American dry diagonal, from Caatinga through Cerrado, Chaco, and Pampas, highlight the importance of drier biomes as corridors for movement. Routes from the Pampas toward both the Atlantic Forest and the Amazon Forest suggest more recent expansions into these areas.

A non-parametric statistical comparison of surface paleotemperatures grouped by dispersal phase revealed significant differences among all three phases, supporting the exploratory association between climate fluctuations and Triatominae dispersal dynamics. The researchers caution that this comparison is exploratory, but the alignment of the biphasic dispersal pattern with major paleotemperature shifts implies a potential influence of climatic change on the evolutionary dispersal processes of this medically important insect group. Individual routes also showed varying temporal peaks, with the bidirectional exchange between Mesoamerica and the Nearctic displaying distinct modes of activity, one peaking around 13 to 15 million years ago and another more recent.

The findings carry epidemiological weight because nearly all Triatominae species serve as vectors for Trypanosoma cruzi, the protozoan that causes Chagas disease, and understanding the historical processes that shaped their distribution may inform how these vectors respond to future environmental change. The study drew on a robust dataset of 18,438 unique occurrence records from the DataTri database, and the regionalization revealed that 54 percent of species were restricted to a single bioregion, underscoring how strongly dispersal history continues to define contemporary patterns of kissing bug diversity across the Americas. By quantifying the timing and directionality of lineage dispersals, the researchers have provided a macroevolutionary framework that connects deep-time biogeography with the present-day geography of one of the most consequential insect vectors in the Neotropics.

Subject of Research: Historical biogeography and dispersal timing of Triatominae (kissing bugs) across the Neotropics

Article Title: Timing and directionality of Triatominae ( Hemiptera , Reduviidae ) lineage dispersals in the Neotropics

Article References: Cardozo, M. D. L. B., Rabinovich, J. E., Lepeco, A., & Löwenberg-Neto, P. (2025). Timing and directionality of Triatominae (Hemiptera, Reduviidae) lineage dispersals in the Neotropics. Frontiers of Biogeography, 18, Article e132274. https://doi.org/10.21425/fob.18.132274

Image Credits: AI Generated

DOI: 10.21425/fob.18.132274

Keywords: Timing, directionality, Triatominae, Hemiptera, Reduviidae, lineage, dispersals, Neotropics, scientific research

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