Genetic Structure of Brazilian Populations of Triatoma sordida (Stål, 1859) (Hemiptera, Triatominae) by Means of Chromosomal Markers

Characterization of Female External Genitalia and Eggs of Four South American Species of the Triatoma Laporte, 1832 Genus (Hemiptera: Reduviidae: Triatominae)

Simple Summary

We present a morphological and morphometric study with T. garciabesi, T. guasayana, T. patagonica, and T. sordida sensu stricto species within the Triatoma genus. This group of species is important for the eco-epidemic scenario of Chagas disease in the Americas; their species have morphological, biological, and behavioral similarities that make diagnosis difficult. For the first time, the description of the female external genitalia by scanning electron microscopy (SEM), a character that has helped with the delimitation of species and genera in Triatominae, is published, in addition to presenting an extensive study with eggs, covering morphology and morphometry. The study with eggs is an important tool in taxonomic studies of the subfamily. In addition to taxonomic contributions, it was possible through the descriptions to corroborate the validity of T. garciabesi and confirm the current classification of these species.

Abstract

Triatoma is the most diversified and one of the most important genera from an epidemiological perspective. Given the difficulty in identifying some species of the Triatoma genus, morphological, histological, and morphometric studies were performed to provide new characters that make it possible to differentiate T. garciabesi, T. guasayana, T. patagonica, and T. sordida sensu stricto, triatomines that overlap geographically and have vector potential. Through the external female genitalia, as well as morphology, morphometry, and histology of eggshells, it was possible to discriminate the four species. In addition, this study reinforces the taxonomic validity of T. garciabesi and provides new data for discussion on systematic issues of T. guasayana and T. patagonica.

Phylogenetic and phenotypic relationships of the Triatoma sordida subcomplex (Hemiptera: Reduviidae: Triatominae)

Chagas disease, whose etiological agent is the protozoan Trypanosoma cruzi, affects millions of people worldwide and it is mainly transmitted by infected triatomine feces. Triatoma is the most diverse genus and one of the most important from an epidemiological point of view. Species of this genus are grouped into eight complexes and nine subcomplexes. Triatoma sordida subcomplex consists of T. garciabesi, T. guasayana, T. patagonica, and, T. sordida. Given the recent discussions on their phylogenetic status, this study aims to evaluate morphometric and genetics characters that group and distinguish T. garciabesi, T. guasayana, T. patagonica, and T. sordida, as well as to infer the phylogenetic relationships within the group and evaluate the proximity with T. rubrovaria subcomplex. The results corroborate the phylogenetic relationship of T. guasayana and T. patagonica with the T. rubrovaria subcomplex. Molecular data confirm the proximity of T. jurbergi, T. matogrossensis, T. vandae as T. garciabesi, and T. sordida. Together, genetic variability was shown between T. sordida populations.

Revisiting the genetic variability of Brazilian peridomestic populations of the Chagas disease vector Triatoma sordida () (Hemiptera, Triatominae)

Triatoma sordida is an endemic species to South America, currently considered the species most frequently found in the peridomestic environment in Brazil. This triatomine has a wide ecological tolerability that allows it to inhabit several ecotopes and use different food sources. Although the species is considered predominantly peridomestic, it is also capable of colonizing households and forming numerous intra-household colonies, leading to its inclusion among the priorities for triatomine control campaigns in Brazil. All Brazilian populations of T. sordida are considered as T. sordida sensu stricto by chromosomal analyses (which highlights their epidemiological importance), although molecular studies that characterize the genetic diversity of these populations are scarce, being restricted only to the region of Minas Gerais. Thus, several populations of this vector distributed in the states of Bahia, Goiás, Mato Grosso do Sul, and Minas Gerais were analyzed using mitochondrial markers (cyt b and nd1). Low nucleotide diversity, high haplotypic diversity, low genetic distance, and high F_ST value were observed, as well as the formation of a monophyletic clade of the Brazilian populations of T. sordida, which confirms that this species has low genetic variability, with all specimens in Brazil grouped in T. sordida sensu stricto. In addition to the genetic and evolutionary importance for the knowledge of the biology of these vectors, these results are important from an epidemiological point of view, thus being able to direct vector control programs.

Drivers of molecular and morphometric variation in Triatoma brasiliensis (Hemiptera: Triatominae): the resolution of geometric morphometrics for populational structuring on a microgeographical scale

Background

The protozoan Trypanosoma cruzi circulates in semiarid areas of northeastern Brazil in distinct ecotopes (sylvatic, peridomestic and domestic) where Triatoma brasiliensis Neiva, 1911 is the most important Chagas disease vector. In this study, we analyzed microevolutionary and demographic aspects of T. brasiliensis populations at the ecotypic, micro and macro-geographic scales by combining morphometrics and molecular results. Additionally, we aimed to address the resolution of both markers for delimiting populations in distinct scales.

Methods

We sampled populations of T. brasiliensis from distinct ecotypic and geographic sites in the states Rio Grande do Norte (RN) and Paraíba (PB). The geometric morphometry was carried out with 13 landmarks on the right wings (n = 698) and the genetic structure was assessed by sequencing a region of cytochrome b mitochondrial gene (n = 221). Mahalanobis distance (MD) and coefficient of molecular differentiation (Φ_ST) were calculated among all pairs of populations. The results of comparisons generated MD and Φ_ST dendrograms, and graphics of canonical variate analysis (CVA).

Results

Little structure was observed for both markers for macro-geographic scales. Mantel tests comparing geographic, morphometric and genetic matrices showed low correlation (all R² < 0.35). The factorial graphics built with the CVA evidenced population delimitation for the morphometric data at micro-geographic scales.

Conclusions

We believe that T. brasiliensis carries in its genotype a source of information to allow the phenotypical plasticity across its whole distribution for shaping populations, which may have caused a lack of population delimitation for CVAs in morphometric analysis for macro-geographic scale analysis. On the other hand, the pattern of morphometric results in micro-geographic scales showed well-defined groups, highlighting the potential of this tool to inferences on the source for infestation.

Population genetics of two chromatic morphs of the Chagas disease vector Rhodnius pallescens Barber, 1932 in Panamá

Rhodnius pallescens is the principal vector of Chagas disease in Panama. Recently a dark chromatic morph has been discovered in the highlands of Veraguas Province. Limited genetic studies have been conducted with regards to the population structure and dispersal potential of Triatominae vectors, particularly in R. pallescens. Next generation sequencing methods such as RADseq and complete mitochondrial DNA (mtDNA) genome sequencing have great potential for examining vector biology across space and time. Here we utilize a RADseq method (3RAD), along with complete mtDNA sequencing, to examine the population structure of the two chromatic morpho types of R. pallescens in Panama. We sequenced 105 R. pallescens samples from five localities in Panama. We generated a 2216 SNP dataset and 6 complete mtDNA genomes. RADseq showed significant differentiation among the five localities (F_CT = 0.695; P = .004), but most of this was between localities with the dark vs. light chromatic morphs (Veraguas vs. Panama Oeste). The mtDNA genomes showed a 97-98% similarity between dark and light chromatic morphs across all genes and a 502 bp insert in light morphs. Thus, both the RADseq and mtDNA data showed highly differentiated clades with essentially no gene flow between the dark and light chromatic morphs from Veraguas and central Panama respectively. We discuss the growing evidence showing clear distinctions between these two morpho types with the possibility that these are separate species, an area of research that requires further investigation. Finally, we discuss the cost-effectiveness of 3RAD which is a third of the cost compared to other RADseq methods used recently in Chagas disease vector research.