Filogeografia, morfometria e distribuição geográfica potencial de populações de Rhodnius neglectus (Hemiptera, Reduviidae) no Brasil

AUTOR(ES)
DATA DE PUBLICAÇÃO

2008

RESUMO

Sylvatic triatomines of the genus Rhodnius commonly fly into houses in Latin America, maintaining the risk of Chagas disease transmission. In this thesis, phylogeographical, morphological and potential geographical distribution analyses of Rhodnius populations in central Brazil were carried out, focusing in R. neglectus, the major species found in palm trees in the Brazilian Savannah. Bugs were captured in Mautitia flexuosa palm trees from four hydrogeographic basins (Tocantins, São Francisco, Parana and Paraguay); the infestation and trypanosomatid infection indices were analyzed. Geometric morphometric methods were applied to identify the Rhodnius species of the R. prolixus group and to analyze the morphometric variation among R. neglectus populations from these basins. The hypothesis of phenotypic plasticity related to some environment variables was also tested. The potential geographical distribution of R. neglectus was analyzed by using ecological niche modeling (GARP) based on the relation of environmental variables and occurrence records. The phylogeographic analyses of R. neglectus populations were based on polymorphisms of cytochrome b sequences, testing the hypotheses of differentiation and isolation by distance. The frequency of infested palms varied from 11 to 100% in the 40 sampled areas, and 1,581 specimens were collected in 177 palms, mainly in bird nests; 3.8% of the examined bugs were infected by trypanosomatids (Trypanosoma cruzi and T. rangeli). Morphometric analyses of shape variation allowed for an almost perfect reclassification of individuals to their putative species. Shape patterning revealed no consistent differences between most specimens collected inside houses in central Brazil and R. neglectus, and also showed that R. robustus and R. neglectus occur sympatrically in southern Amazonia. These results strongly support the idea that R. neglectus, and not R. prolixus, is the species invading houses in central Brazil. The geometric morphometric methods applied to assess the intraspecific phenotypic variation in R. neglectus showed significant size variation among populations.Wing and head size were influenced by temperature: the smallest specimens were found in the coldest areas. Nevertheless, no significant shape variation was observed among populations of different geographical basins. The ecological niche models were able to predict the occurrence of R. neglectus as a characteristic (although not endemic) species of the Cerrado biome. Meanwhile, Caatinga, Amazonian savannas, Pantanal, and the Bolivian Chaco appear as areas with lower predicted presence probability for the species. A high overlap was observed among the distributions of R. neglectus, some palm trees and birds. By including new records for R. neglectus, the present study has revealed a wider distribution towards the west and northeast areas of Brazil in the diagonal of open/dry ecoregions of South America. The sequencing of 5- end of the cytochrome b gene in 144 individuals from 33 populations resulted in a fragment of 567bp, revealing the existence of 13 different haplotypes and 22 variable sites. These haplotypes formed a well-supported monophyletic group identified as R. neglectus and clearly separated for other Rhodnius species of the R. prolixus group. The two more frequent haplotypes occurred in areas separated by a distance over 1,700 km and from three different hydrogeographic basins. Shared haplotypes were also observed in areas from both sides of large rivers and both sides of Serra Geral de Goiás. The populations from Alto Paraíso-GO and from the Paraguay basin (Mato Grosso) presented unique haplotypes and higher levels of nucleotide diversity and divergence among populations. The haplotype network analysis showed two geographically distinct groups (western and eastern) but there was no evidence of isolation by distance (Mantel, p = 0,446). The dispersal of R. neglectus specimens among the basins may occur through passive carriage by birds. Finally, these results should help the Chagas disease vector surveillance program, given that household invasion by Rhodnius species maintains disease transmission risk and limits the effectivenes of control strategies.

ASSUNTO(S)

rhodnius neglectus phylogeography rhodnius neglectus geographical distribution filogeografia brazil distribuição geográfica brasil ciencias da saude morfometria geométrica doença de chagas geometric morphometrics garp vector surveillance garp cerrado cerrado chagas disease vigilância entomológica

ACESSO AO ARTIGO

Documentos Relacionados