Biogeography of Brazilian populations of Panstrongylus megistus (Hemiptera, Reduviidae, Triatominae) based on molecular marker and paleo-vegetational data
Introduction
Triatomine bugs (Hemiptera, Reduviidae) are vectors of the protozoan Trypanosoma cruzi Chagas, 1909, causative agent of American trypanosomiasis or Chagas disease. In some parts of the southeastern and northeastern Brazilian regions, Panstrongylus megistus Burmeister, 1835 is the most important vector of the disease. The original morphoclimatic domain of this species was the Atlantic tropics, and its domiciliation resulted from human destruction of its natural forest habitats. This species has a wide geographical distribution, being found in the morphoclimatic domains of the tropical Atlantic, cerrado (similar to the savanna) and Atlantic forest remnants (Instituto Sócio Ambiental, 2001) lying within the caatingas (dry, open forest). In these areas, islands of original forest surrounded by grassland have allowed P. megistus populations to survive in geographical isolation (Forattini, 1980).
According to Forattini et al. (1978) and Forattini (1980), São Paulo is the center of endemism for P. megistus, together with parts of the Brazilian states of Pernambuco, Bahia and Rio de Janeiro. The species spread westwards from these centers, reaching different regions of humid forest surrounded by open habitats (Forattini, 1980). Barbosa et al. (2003) suggested that Minas Gerais may also have been an endemic center of this species, based on the greater genetic variability observed in three P. megistus populations.
By measuring genetic variations and applying population genetic models, we can make inferences regarding the biology of organisms (Sunnucks, 2000). The DNA polymorphisms generated by random amplification of polymorphic DNA (RAPD) provide a molecular basis that allows taxonomic relationships among the Triatominae to be reassessed (Garcia et al., 1998). RAPD analysis is also an important tool in population studies of this group of insects, particularly with regard to intra- and inter-specific differentiation (Garcia et al., 1998, Dujardin et al., 1998, Borges et al., 2000, Borges et al., 2005, Jaramillo et al., 2001, Lopes et al., 2001, Pacheco et al., 2003).
The environmental history of Brazil remains little-known, like that of South America in general. Understanding the association between previous environmental changes, current geographical distribution and genetic characterization of individuals are fundamental to understand the behavioral biology of triatomines and is important for epidemiological evaluation of Chagas’ disease control programs. Thus in this study, we sought to establish a link between genetic variability in P. megistus using the RAPD technique and South American biogeographical data, with a view to better understanding the origin and population organization of this species.
Section snippets
Insects
Specimens of P. megistus were obtained from different ecotopes, geographical regions and morphoclimatic domains of Brazil, as shown in Fig. 1 and Table 1. First generation (F1) adult insects were reared in the laboratory (27 °C ± 2 °C; 60% ± 10% RH) and fed every 2 weeks on chickens. Note: The symbols adopted here to identify the populations do not follow the pattern adopted in Barbosa et al. (2004), although most of the populations studied are the same.
RAPD
After preliminary intrapopulational analysis
RAPD
Interpopulational heterogeneity can be observed based on profiles obtained from each primer, equivalent to complexes (Fig. 2a and b). In all, 143 bands were analyzed for the band-sharing analysis, limited to 190–800 bp amplification products generated by the 4 primers used. Bands were selected for comparative analysis according to their intensity, resolution and reproducibility. The phenogram obtained (Fig. 3) showed slight differentiation of the individuals in geographical populations, the most
Discussion
In the present study, intrapopulational analysis by RAPD showed genetic variability among individuals of the same population, without showing sexual differentiation for most of the populations studied (data not shown). Interpopulational analysis revealed a high level of differentiation among the P. megistus populations studied, with clear geographical separation (Fig. 3), coinciding with the current morphoclimatic domains in their ranges.
The data obtained from RAPD may help explain the
Acknowledgements
We thank Dr. Márcio Vinhaes (DF), Bernardino Vaz de Mello Azeredo (MG), Maria Valentini (BA), João Leite (AL), Lindenberg de Souza (CE), Antônio Ciro dos Santos (Bocaiúva/MG), Hermínio Severino (Carmo do Paranaíba/MG) of the Fundação Nacional da Saúde (FUNASA), as well as field technicians of this institution who helped us collect insects in the various states; we also thank Dr. Mário Steindel (UFSC/SC), Dr. Rogério Luiz Koop (UFPR) and Dra. Vera Rodrigues (Sucen/SP) for support during insect
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2022, Acta TropicaCitation Excerpt :An analysis with ITS-2 sequences revealed less interpopulation divergence in P. megistus than in other species (Marcilla et al., 2002). The RAPD markers (Barbosa et al., 2006) and CytB (Vendrami et al., 2014) differentiated populations from Northeastern Brazil from those from the Southeast and South. Cavassin et al. (2014) showed great haplotypic variability compared to other species using ITS-1 and ITS-2.
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2018, Advances in ParasitologyCitation Excerpt :P. megistus is widespread across the Atlantic forests but also occurs in gallery forests throughout the drier Cerrado and stretches into the semiarid Caatinga, the Chaco, and parts of the Pantanal and Uruguayan savannahs (Barbosa et al., 2006; Barrett, 1991; Cavassin et al., 2014; Forattini, 1980; Galvão, 2014; Gurgel-Gonçalves et al., 2012; Lent and Wygodzinsky, 1979; Patterson et al., 2009; Silveira et al., 1984). Southern P. megistus populations seem tightly associated with humid forests and rarely, if ever, colonize in man-made habitats, whereas populations in seasonally drier regions are important domestic vectors (Barbosa et al., 2003, 2006; Forattini, 1980; Forattini et al., 1978; Lent and Wygodzinsky, 1979). T. tibiamaculata is associated with palms and bromeliads along a narrow strip of coastal Brazil including the Pernambuco, Bahia, and Serra do Mar coastal moist forests (Barrett, 1991; Galvão, 2014; Gurgel-Gonçalves et al., 2012; Lent and Wygodzinsky, 1979).
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2009, Acta TropicaCitation Excerpt :P. megistus may have begun to invade the domestic environment during the post-colonial period; following the destruction of its natural habitat and consequent agricultural developments, this species presumably invaded and adapted to exploit domestic environments (Litvoc et al., 1990). Barbosa et al. (2006) observed great diversity in populations of P. megistus, this was considered in the context of paleovegetation reconstruction. The local paleovegetation record shows a clear process of expansion and retraction of humid forest during the last ∼18,000 years, and can account for the observed fragmented population structure.
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