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Does Triatoma brasiliensis occupy the same environmental niche space as Triatoma melanica?

de Souza Rde C, Campolina-Silva GH, Bezerra CM, Diotaiuti L, Gorla DE - Parasit Vectors (2015)

Bottom Line: The ecological niche models show that the environmental spaces currently occupied by T. brasiliensis and T. melanica are similar although not equivalent, and associated with the caatinga ecosystem.Wing size and shape analyses based on seven landmarks of 72 field specimens confirmed consistent differences between T. brasiliensis and T. melanica.Our results suggest that the separation of the two species should be attributed to a factor that does not include the current environmental conditions.

View Article: PubMed Central - PubMed

Affiliation: Laboratório de Triatomíneos e Epidemiologia da Doença de Chagas, Centro de Pesquisas René Rachou, Fundação Oswaldo Cruz, CEP 30.190-002, Belo Horizonte, Minas Gerais, Brazil. rita@cpqrr.fiocruz.br.

ABSTRACT

Background: Triatomines (Hemiptera, Reduviidae) are vectors of Trypanosoma cruzi, the causative agent of Chagas disease, one of the most important vector-borne diseases in Latin America. This study compares the environmental niche spaces of Triatoma brasiliensis and Triatoma melanica using ecological niche modelling and reports findings on DNA barcoding and wing geometric morphometrics as tools for the identification of these species.

Methods: We compared the geographic distribution of the species using generalized linear models fitted to elevation and current data on land surface temperature, vegetation cover and rainfall recorded by earth observation satellites for northeastern Brazil. Additionally, we evaluated nucleotide sequence data from the barcode region of the mitochondrial cytochrome c oxidase subunit I (CO1) and wing geometric morphometrics as taxonomic identification tools for T. brasiliensis and T. melanica.

Results: The ecological niche models show that the environmental spaces currently occupied by T. brasiliensis and T. melanica are similar although not equivalent, and associated with the caatinga ecosystem. The CO1 sequence analyses based on pair wise genetic distance matrix calculated using Kimura 2-Parameter (K2P) evolutionary model, clearly separate the two species, supporting the barcoding gap. Wing size and shape analyses based on seven landmarks of 72 field specimens confirmed consistent differences between T. brasiliensis and T. melanica.

Conclusion: Our results suggest that the separation of the two species should be attributed to a factor that does not include the current environmental conditions. However, as the caatinga is a biome that has existed in the area for at least the last 18,000 years, past conditions might have had an influence in the speciation process. The DNA Barcoding approach may be extended to these members of the subfamily Triatominae.

No MeSH data available.


Related in: MedlinePlus

Shape variation in T. brasiliensis and T. melanica. (A) Factorial map showing the distribution of specimens in the plane of the two discriminant factors derived from discriminant analysis of the shape variables. Polygons correspond to each group under study, where continuous polygons enclose males and dotted polygons enclose females. DF1 and DF2 are the first and second discriminate factors, and their corresponding percentage contribution to the total shape variation is shown in parentheses. (B) Wing consensus shape obtained after the Generalized Procrustes Analyses (GPA). Arrows indicate the major differences in wing shape of T. brasiliensis and T. melanica
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Fig3: Shape variation in T. brasiliensis and T. melanica. (A) Factorial map showing the distribution of specimens in the plane of the two discriminant factors derived from discriminant analysis of the shape variables. Polygons correspond to each group under study, where continuous polygons enclose males and dotted polygons enclose females. DF1 and DF2 are the first and second discriminate factors, and their corresponding percentage contribution to the total shape variation is shown in parentheses. (B) Wing consensus shape obtained after the Generalized Procrustes Analyses (GPA). Arrows indicate the major differences in wing shape of T. brasiliensis and T. melanica

Mentions: The first two discriminant factors (DF1 and DF2) explained 94 % and 4 % of wing shape variation, respectively. T. brasiliensis and T. melanica were significantly different (P < 0.01) and well separated in a factorial map of discriminant analysis along the DF1 axis (Fig. 3a). T. melanica wings were narrow when compared with T. brasiliensis, and the landmarks 3 and 7 better contributed to the conformational changes in wing venation (Fig. 3b), and are important in the discrimination of these species. Significant Mahalanobis distances could be found between species and sexes after the permutation test corrected by Bonferroni (P <0.05), except for males and females of T. brasiliensis. The UPGMA dendrogram derived from these distances showed a clear separation between the species (Fig. 4). The multivariate regression analyses of the first two shape discriminant factors (DF1 and DF2) against the centroid size values revealed no significant contribution of size to shape variation (no allometric content, p = 0.19).Fig. 3


Does Triatoma brasiliensis occupy the same environmental niche space as Triatoma melanica?

de Souza Rde C, Campolina-Silva GH, Bezerra CM, Diotaiuti L, Gorla DE - Parasit Vectors (2015)

Shape variation in T. brasiliensis and T. melanica. (A) Factorial map showing the distribution of specimens in the plane of the two discriminant factors derived from discriminant analysis of the shape variables. Polygons correspond to each group under study, where continuous polygons enclose males and dotted polygons enclose females. DF1 and DF2 are the first and second discriminate factors, and their corresponding percentage contribution to the total shape variation is shown in parentheses. (B) Wing consensus shape obtained after the Generalized Procrustes Analyses (GPA). Arrows indicate the major differences in wing shape of T. brasiliensis and T. melanica
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4496957&req=5

Fig3: Shape variation in T. brasiliensis and T. melanica. (A) Factorial map showing the distribution of specimens in the plane of the two discriminant factors derived from discriminant analysis of the shape variables. Polygons correspond to each group under study, where continuous polygons enclose males and dotted polygons enclose females. DF1 and DF2 are the first and second discriminate factors, and their corresponding percentage contribution to the total shape variation is shown in parentheses. (B) Wing consensus shape obtained after the Generalized Procrustes Analyses (GPA). Arrows indicate the major differences in wing shape of T. brasiliensis and T. melanica
Mentions: The first two discriminant factors (DF1 and DF2) explained 94 % and 4 % of wing shape variation, respectively. T. brasiliensis and T. melanica were significantly different (P < 0.01) and well separated in a factorial map of discriminant analysis along the DF1 axis (Fig. 3a). T. melanica wings were narrow when compared with T. brasiliensis, and the landmarks 3 and 7 better contributed to the conformational changes in wing venation (Fig. 3b), and are important in the discrimination of these species. Significant Mahalanobis distances could be found between species and sexes after the permutation test corrected by Bonferroni (P <0.05), except for males and females of T. brasiliensis. The UPGMA dendrogram derived from these distances showed a clear separation between the species (Fig. 4). The multivariate regression analyses of the first two shape discriminant factors (DF1 and DF2) against the centroid size values revealed no significant contribution of size to shape variation (no allometric content, p = 0.19).Fig. 3

Bottom Line: The ecological niche models show that the environmental spaces currently occupied by T. brasiliensis and T. melanica are similar although not equivalent, and associated with the caatinga ecosystem.Wing size and shape analyses based on seven landmarks of 72 field specimens confirmed consistent differences between T. brasiliensis and T. melanica.Our results suggest that the separation of the two species should be attributed to a factor that does not include the current environmental conditions.

View Article: PubMed Central - PubMed

Affiliation: Laboratório de Triatomíneos e Epidemiologia da Doença de Chagas, Centro de Pesquisas René Rachou, Fundação Oswaldo Cruz, CEP 30.190-002, Belo Horizonte, Minas Gerais, Brazil. rita@cpqrr.fiocruz.br.

ABSTRACT

Background: Triatomines (Hemiptera, Reduviidae) are vectors of Trypanosoma cruzi, the causative agent of Chagas disease, one of the most important vector-borne diseases in Latin America. This study compares the environmental niche spaces of Triatoma brasiliensis and Triatoma melanica using ecological niche modelling and reports findings on DNA barcoding and wing geometric morphometrics as tools for the identification of these species.

Methods: We compared the geographic distribution of the species using generalized linear models fitted to elevation and current data on land surface temperature, vegetation cover and rainfall recorded by earth observation satellites for northeastern Brazil. Additionally, we evaluated nucleotide sequence data from the barcode region of the mitochondrial cytochrome c oxidase subunit I (CO1) and wing geometric morphometrics as taxonomic identification tools for T. brasiliensis and T. melanica.

Results: The ecological niche models show that the environmental spaces currently occupied by T. brasiliensis and T. melanica are similar although not equivalent, and associated with the caatinga ecosystem. The CO1 sequence analyses based on pair wise genetic distance matrix calculated using Kimura 2-Parameter (K2P) evolutionary model, clearly separate the two species, supporting the barcoding gap. Wing size and shape analyses based on seven landmarks of 72 field specimens confirmed consistent differences between T. brasiliensis and T. melanica.

Conclusion: Our results suggest that the separation of the two species should be attributed to a factor that does not include the current environmental conditions. However, as the caatinga is a biome that has existed in the area for at least the last 18,000 years, past conditions might have had an influence in the speciation process. The DNA Barcoding approach may be extended to these members of the subfamily Triatominae.

No MeSH data available.


Related in: MedlinePlus