140 research outputs found

    Phylogenetic structure of geographical co-occurrence among New World Triatominae species, vectors of Chagas disease

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    The tropical niche conservatism (TNC) hypothesis is one of the most prominent evolutionary hypotheses that has been supported as an explanation for the diversity gradients of several animal taxa, mainly vertebrates. However, the validity of TNC for less-known taxa such as disease vectors is not clear. Here, we test predictions of TNC in driving the geographical co-occurrence among triatomine species, vector insects of Chagas disease. We aim to infer the relative effects of ecological and evolutionary processes in determining triatomine species richness at broad spatial scales. Location: America. Taxon: Triatominae (Hemiptera: Reduviidae). Methods: We gathered distributional, phylogenetic and climatic information for 63 triatomine species. We apply the phylogenetic field (PF) framework based on the phylogenetic structure of species co-occurrences, considering their climatic preferences. We defined PFs of species by estimating the phylogenetic structure of species co-occurrence within a focal species’ range. Likewise, climatic conditions within focal species’ ranges were defined as their preferred climates. We applied a spatial-phylogenetic statistical framework to evaluate geographical variation of species’ co-occurrence and tested the significance of PFs based on biogeographically informed null models. Results: Phylogenetic fields of 17 out of 59 triatomine species showed a trend from overdispersed to clustered, coincident with tropical to subtropical–temperate climate. Triatomines co-occur with more closely related species in temperate areas and more distantly related species in tropical areas. Temperature seasonality was inversely related to the phylogenetic structure of co-occurrence within species ranges. Main conclusions: Geographical co-occurrence among triatomine species revealed a tropical to subtropical–temperate gradient from overdispersed to clustered PFs and a correspondence between the type of climate in which these species are found and their PFs. Phylogenetic structure within triatomine ranges is explained by their evolutionary history. Our study provides a methodological framework to evaluate the New World triatomine geographical co-occurrence patterns under a phylogenetic perspective and our results make an important contribution to the understanding of the broad-scale biodiversity patterns in Triatominae.Fil: Ceccarelli, Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Estudios Parasitológicos y de Vectores. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Estudios Parasitológicos y de Vectores; ArgentinaFil: Justi, Silvia A.. Smithsonian Institution Museum Support Center; Estados Unidos. Walter Reed Army Institute of Research. Entomology Branch; Estados UnidosFil: Rabinovich, Jorge Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Estudios Parasitológicos y de Vectores. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Estudios Parasitológicos y de Vectores; ArgentinaFil: Diniz Filho, José Alexandre F.. Universidade Federal de Goiás; BrasilFil: Villalobos, Fabricio. Universidade Federal de Goiás; Brasil. Instituto de Ecología; Méxic

    Range size positively correlates with temperature and precipitation niche breadths but not with dietary niche breadth in triatomine insects, vectors of Chagas disease

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    Ecological theory predicts that species that can utilise a greater diversity of resources and, therefore, have wider niche breadths should also occupy larger geographic areas (the ‘niche breadth-range size hypothesis’). Here, we tested this hypothesis for a blood-sucking group of insects of medical significance: the Triatominae (aka ‘kissing bugs’) (Hemiptera: Reduviidae). Given that niches can be viewed from different perspectives, we tested this hypothesis based on both dietary and climatic niches. We assembled the most complete dataset of triatomine feeding patterns to date by reviewing 143 studies from the literature up to 2021 and tested whether the niche breadth-range size hypothesis held for this group for both dietary and climatic components of the niche. Temperature and precipitation niche breadths were estimated from macro-environmental variables, while diet breadth was calculated based on literature data that used PCR and/or ELISA to identify different types of hosts as blood sources per triatomine species. Our results showed that temperature and precipitation niche breadths, but not dietary breadth, were positively correlated with range sizes, independent of evolutionary history among species. These findings support the predictions from the range size-niche breadth hypothesis concerning climate but not diet, in Triatominae. It also shows that support for the niche breadth-range size hypothesis is dependent upon the niche axis under consideration, which can explain the mixed support for this hypothesis in the ecological literature

    Ecological host fitting of Trypanosoma cruzi TcI in Bolivia: mosaic population structure, hybridization and a role for humans in Andean parasite dispersal.

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    An improved understanding of how a parasite species exploits its genetic repertoire to colonize novel hosts and environmental niches is crucial to establish the epidemiological risk associated with emergent pathogenic genotypes. Trypanosoma cruzi, a genetically heterogeneous, multi-host zoonosis, provides an ideal system to examine the sylvatic diversification of parasitic protozoa. In Bolivia, T. cruzi I, the oldest and most widespread genetic lineage, is pervasive across a range of ecological clines. High-resolution nuclear (26 loci) and mitochondrial (10 loci) genotyping of 199 contemporaneous sylvatic TcI clones was undertaken to provide insights into the biogeographical basis of T. cruzi evolution. Three distinct sylvatic parasite transmission cycles were identified: one highland population among terrestrial rodent and triatomine species, composed of genetically homogenous strains (Ar = 2.95; PA/L = 0.61; DAS = 0.151), and two highly diverse, parasite assemblages circulating among predominantly arboreal mammals and vectors in the lowlands (Ar = 3.40 and 3.93; PA/L = 1.12 and 0.60; DAS = 0.425 and 0.311, respectively). Very limited gene flow between neighbouring terrestrial highland and arboreal lowland areas (distance ~220 km; FST = 0.42 and 0.35) but strong connectivity between ecologically similar but geographically disparate terrestrial highland ecotopes (distance >465 km; FST = 0.016-0.084) strongly supports ecological host fitting as the predominant mechanism of parasite diversification. Dissimilar heterozygosity estimates (excess in highlands, deficit in lowlands) and mitochondrial introgression among lowland strains may indicate fundamental differences in mating strategies between populations. Finally, accelerated parasite dissemination between densely populated, highland areas, compared to uninhabited lowland foci, likely reflects passive, long-range anthroponotic dispersal. The impact of humans on the risk of epizootic Chagas disease transmission in Bolivia is discussed

    Trypanosoma cruzi: adaptation to its vectors and its hosts

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    American trypanosomiasis is a parasitic zoonosis that occurs throughout Latin America. The etiological agent, Trypanosoma cruzi, is able to infect almost all tissues of its mammalian hosts and spreads in the environment in multifarious transmission cycles that may or not be connected. This biological plasticity, which is probably the result of the considerable heterogeneity of the taxon, exemplifies a successful adaptation of a parasite resulting in distinct outcomes of infection and a complex epidemiological pattern. In the 1990s, most endemic countries strengthened national control programs to interrupt the transmission of this parasite to humans. However, many obstacles remain to the effective control of the disease. Current knowledge of the different components involved in elaborate system that is American trypanosomiasis (the protozoan parasite T. cruzi, vectors Triatominae and the many reservoirs of infection), as well as the interactions existing within the system, is still incomplete. The Triatominae probably evolve from predatory reduvids in response to the availability of vertebrate food source. However, the basic mechanisms of adaptation of some of them to artificial ecotopes remain poorly understood. Nevertheless, these adaptations seem to be associated with a behavioral plasticity, a reduction in the genetic repertoire and increasing developmental instability

    Large-scale patterns in morphological diversity and species assemblages in Neotropical Triatominae (Heteroptera: Reduviidae)

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    We analysed the spatial variation in morphological diversity (MDiv) and species richness (SR) for 91 species of Neotropical Triatominae to determine the ecological relationships between SR and MDiv and to explore the roles that climate, productivity, environmental heterogeneity and the presence of biomes and rivers may play in the structuring of species assemblages. For each 110 km x 110 km-cell on a grid map of America, we determined the number of species (SR) and estimated the mean Gower index (MDiv) based on 12 morphological attributes. We performed bootstrapping analyses of species assemblages to identify whether those assemblages were more similar or dissimilar in their morphology than expected by chance. We applied a multi-model selection procedure and spatial explicit analyses to account for the association of diversity-environment relationships. MDiv and SR both showed a latitudinal gradient, although each peaked at different locations and were thus not strictly spatially congruent. SR decreased with temperature variability and MDiv increased with mean temperature, suggesting a predominant role for ambient energy in determining Triatominae diversity. Species that were more similar than expected by chance co-occurred near the limits of the Triatominae distribution in association with changes in environmental variables. Environmental filtering may underlie the structuring of species assemblages near their distributional limits.Centro de Estudios Parasitológicos y de Vectore

    Comparative morphometric and molecular genetic analyses of triatominae (Hemiptera: Reduviidae)

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    Triatomine bugs (Hemiptera: Reduviidae: Triatominae) are the vectors of Chagas disease in South and Central America. Chagas disease predominantly affects poor rural communities with simply constructed housing susceptible to infestation by triatomines. Chagas disease is restricted to the Americas largely due to the limited distribution of triatomine bugs. The global diversity of triatomines is -130 species, of which only -10% are known to occur outside the Americas, one species (Triatoma rubrofasciata) is tropicopolitan, and the others are concentrated on the Indian subcontinent (Linshcosteus spp. ) and adjacent south east Asian island groups (Triatoma spp. ). The main objectives of this PhD programme were to: a) assess the facility of morphometric approaches (measurement and robust statistical analysis of morphological variation) in the study of population structure of vector species with proximal domestic and silvatic distributions to detect population structure and give information on the risk of reinvasion, b) study interspecific and higher taxonomic level relationships of New World and Old World triatomine bugs. To these ends geometric morphometric analyses were conducted in concert with molecular genetic analyses of mitochondrial and nuclear DNA sequences. The principal question being: Does the relatively low cost method of morphometrics reveal patterns consistent with population structure, as otherwise determined by more expensive molecular genotyping methods? Or are such patterns disrupted by environmental effects and intraspecific convergent/divergent morphological evolution? Combined morphometrics and molecular genetics were used to study vector populations in three of the countries that continue to be most affected by Chagas disease. In Venezuela and Ecuador Rhodnius species (R. prolixus and R. ecuadoriensis respectively) were studied, in areas where they occur in both domestic and silvatic environments, and in Paraguay T. infestans from a domestic and a putative silvatic focus. Head and wing morphometrics were compared to mitochondrial DNA sequence data to assess the population structure and disparity among domestic and silvatic samples in each case. The results presented suggest that head shape variation is subject to morphological plasticity and/or selective pressure and functional constraint and does not correlate well with the 11 Abstract phylogeny. However, in all examples, wing shape was found to be congruent with the phylogenetic patterns inferred from sequence analysis. Consequently, it is recommended that wing shape and not head shape be used in morphometric assessments of population dynamics. It is also asserted here that if population structure is suggested by morphometrics, it should be followed by robust population genetic analysis. As such, morphometrics could be used as a tool for broad surveillance to identify areas of concern. A further objective was to elucidate the broader phylogeny of Triatominae and their relationships with other reduviid subfamilies. To investigate the debated polyphyletic origin of the Triatominae molecular approaches were used. Combined head and wing morphometric and molecular genetic analyses of New World and Old World Triatominae have revealed patterns of convergent morphological evolution (among New World and Old World Triatoma) and striking examples of strongly divergent morphological evolution (between Old World Triatoma and Linshcosteus). Applying a molecular clock based on the rate of sequence divergence for a fragment of ribosomal DNA (D2-28S), calibrated to the fossil record and vicariant events (the divergence of ancestral lineages due to separation by topographical or ecological barriers) it has been possible to reconstruct a likely evolutionary history for the Triatominae and the Reduviidae as a whole. The weight of evidence presented supports a polyphylectic origin for blood-feeding for the Triatominae. The apparent independent development of blood feeding among the main lineages of the Triatominae represented by the genera Triatoma and Rhodnius highlights a fundamental biological difference among important vector species. This difference is likely to become evident in the eventual post genomic era in studies of vector/parasite interactions and it highlights the importance of sequencing genomes from different vector genera.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

    Comparative morphometric and molecular genetic analyses of triatominae (Hemiptera: Reduviidae)

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    Triatomine bugs (Hemiptera: Reduviidae: Triatominae) are the vectors of Chagas disease in South and Central America. Chagas disease predominantly affects poor rural communities with simply constructed housing susceptible to infestation by triatomines. Chagas disease is restricted to the Americas largely due to the limited distribution of triatomine bugs. The global diversity of triatomines is -130 species, of which only -10% are known to occur outside the Americas, one species (Triatoma rubrofasciata) is tropicopolitan, and the others are concentrated on the Indian subcontinent (Linshcosteus spp. ) and adjacent south east Asian island groups (Triatoma spp. ). The main objectives of this PhD programme were to: a) assess the facility of morphometric approaches (measurement and robust statistical analysis of morphological variation) in the study of population structure of vector species with proximal domestic and silvatic distributions to detect population structure and give information on the risk of reinvasion, b) study interspecific and higher taxonomic level relationships of New World and Old World triatomine bugs. To these ends geometric morphometric analyses were conducted in concert with molecular genetic analyses of mitochondrial and nuclear DNA sequences. The principal question being: Does the relatively low cost method of morphometrics reveal patterns consistent with population structure, as otherwise determined by more expensive molecular genotyping methods? Or are such patterns disrupted by environmental effects and intraspecific convergent/divergent morphological evolution? Combined morphometrics and molecular genetics were used to study vector populations in three of the countries that continue to be most affected by Chagas disease. In Venezuela and Ecuador Rhodnius species (R. prolixus and R. ecuadoriensis respectively) were studied, in areas where they occur in both domestic and silvatic environments, and in Paraguay T. infestans from a domestic and a putative silvatic focus. Head and wing morphometrics were compared to mitochondrial DNA sequence data to assess the population structure and disparity among domestic and silvatic samples in each case. The results presented suggest that head shape variation is subject to morphological plasticity and/or selective pressure and functional constraint and does not correlate well with the 11 Abstract phylogeny. However, in all examples, wing shape was found to be congruent with the phylogenetic patterns inferred from sequence analysis. Consequently, it is recommended that wing shape and not head shape be used in morphometric assessments of population dynamics. It is also asserted here that if population structure is suggested by morphometrics, it should be followed by robust population genetic analysis. As such, morphometrics could be used as a tool for broad surveillance to identify areas of concern. A further objective was to elucidate the broader phylogeny of Triatominae and their relationships with other reduviid subfamilies. To investigate the debated polyphyletic origin of the Triatominae molecular approaches were used. Combined head and wing morphometric and molecular genetic analyses of New World and Old World Triatominae have revealed patterns of convergent morphological evolution (among New World and Old World Triatoma) and striking examples of strongly divergent morphological evolution (between Old World Triatoma and Linshcosteus). Applying a molecular clock based on the rate of sequence divergence for a fragment of ribosomal DNA (D2-28S), calibrated to the fossil record and vicariant events (the divergence of ancestral lineages due to separation by topographical or ecological barriers) it has been possible to reconstruct a likely evolutionary history for the Triatominae and the Reduviidae as a whole. The weight of evidence presented supports a polyphylectic origin for blood-feeding for the Triatominae. The apparent independent development of blood feeding among the main lineages of the Triatominae represented by the genera Triatoma and Rhodnius highlights a fundamental biological difference among important vector species. This difference is likely to become evident in the eventual post genomic era in studies of vector/parasite interactions and it highlights the importance of sequencing genomes from different vector genera.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

    Triatomines: Trypanosomatids, Bacteria, and Viruses Potential Vectors? [Review]

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    Triatominae bugs are the vectors of Chagas disease, a major concern to public health especially in Latin America, where vector-borne Chagas disease has undergone resurgence due mainly to diminished triatomine control in many endemic municipalities. Although the majority of Triatominae species occurs in the Americas, species belonging to the genus Linshcosteus occur in India, and species belonging to the Triatoma rubrofasciata complex have been also identified in Africa, the Middle East, South-East Asia, and in the Western Pacific. Not all of Triatominae species have been found to be infected with Trypanosoma cruzi, but the possibility of establishing vector transmission to areas where Chagas disease was previously non-endemic has increased with global population mobility. Additionally, the worldwide distribution of triatomines is concerning, as they are able to enter in contact and harbor other pathogens, leading us to wonder if they would have competence and capacity to transmit them to humans during the bite or after successful blood feeding, spreading other infectious diseases. In this review, we searched the literature for infectious agents transmitted to humans by Triatominae. There are reports suggesting that triatomines may be competent vectors for pathogens such as Serratia marcescens, Bartonella, and Mycobacterium leprae, and that triatomine infection with other microrganisms may interfere with triatomine-T. cruzi interactions, altering their competence and possibly their capacity to transmit Chagas disease

    Triatomines : trypanosomatids, bacteria, and viruses potential vectors?

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    Triatominae bugs are the vectors of Chagas disease, a major concern to public health especially in Latin America, where vector-borne Chagas disease has undergone resurgence due mainly to diminished triatomine control in many endemic municipalities. Although the majority of Triatominae species occurs in the Americas, species belonging to the genus Linshcosteus occur in India, and species belonging to the Triatoma rubrofasciata complex have been also identified in Africa, the Middle East, South-East Asia, and in the Western Pacific. Not all of Triatominae species have been found to be infected with Trypanosoma cruzi, but the possibility of establishing vector transmission to areas where Chagas disease was previously non-endemic has increased with global population mobility. Additionally, the worldwide distribution of triatomines is concerning, as they are able to enter in contact and harbor other pathogens, leading us to wonder if they would have competence and capacity to transmit them to humans during the bite or after successful blood feeding, spreading other infectious diseases. In this review, we searched the literature for infectious agents transmitted to humans by Triatominae. There are reports suggesting that triatominesmay be competent vectors for pathogens such as Serratiamarcescens, Bartonella, andMycobacteriumleprae, and that triatomine infection with other microrganisms may interfere with triatomine-T. cruzi interactions, altering their competence and possibly their capacity to transmit Chagas disease
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