Transcriptome-based molecular systematics: Rhodnius montenegrensis (Triatominae) and its position within the Rhodnius prolixus–Rhodnius robustus cryptic–species complex

Abstract

Background Rhodnius montenegrensis (Triatominae), a potential vector of Chagas disease, was described after R. robustus -like bugs from southwestern Amazonia. Mitochondrial cytb sequence near-identity with sympatric R. robustus (genotype II) raised doubts about the taxonomic status of R. montenegrensis , but comparative studies have reported fairly clear morphological and genetic differences between R. montenegrensis and laboratory stocks identified as R. robustus . Here, we use a transcriptome-based approach to investigate this apparent paradox. Results We retrieved publicly-available transcriptome sequence-reads from R. montenegrensis and from the R. robustus stocks used as the taxonomic benchmark in comparative studies. We (i) aligned transcriptome sequence-reads to mitochondrial ( cytb ) and nuclear (ITS2, D2- 28S and AmpG ) query sequences (47 overall) from members of the R. prolixus – R. robustus cryptic–species complex and related taxa; (ii) computed breadth- and depth-coverage for the 259 consensus sequences generated by these alignments; and, for each locus, (iii) appraised query sequences and full-breadth-coverage consensus sequences in terms of nucleotide-sequence polymorphism and phylogenetic relations. We found evidence confirming that R. montenegrensis and R. robustus genotype II are genetically indistinguishable and, hence, implying that they are, in all likelihood, the same species. Furthermore, we found compelling genetic evidence that the benchmark ‘ R. robustus ’ stocks used in R. montenegrensis description and in later transcriptome-based comparisons are in fact R. prolixus , although likely mixed to some degree with R. robustus (probably genotype II, a.k.a. R. montenegrensis ). Conclusions We illustrate how public-domain genetic/transcriptomic data can help address challenging issues in disease-vector systematics. In our case-study, taxonomic confusion apparently stemmed from the misinterpretation of sequence-data analyses and misidentification of taxonomic-benchmark stocks. More generally, and together with previous reports of mixed and/or misidentified Rhodnius spp. laboratory colonies, our results call into question the conclusions of many studies (on morphology, genetics, physiology, behavior, bionomics or interactions with microorganisms including trypanosomes) based on non-genotyped ‘ R. prolixus ’ or ‘ ...

From qualitative to quantitative insect metabarcoding: an in tandem multilocus mosquito identification methodology

“…On the other hand, 28S rRNA revealed isles of conserved and hypervariable regions (D2, D8 and D10 in Diptera) (Figure 1) known before for their ability to distinguish closely related species. The D2 region has been used in the taxonomy of Acarina, Hymenoptera, Heteroptera and Diptera, including mosquitoes [21][22][23][24][25][26][27] . D8 and D10 regions have been used to a lesser extent in the classification and phylogeny of mites and mealybugs 22,27,28 .…”

Chagas disease vectors identification using visible and near-infrared spectroscopy

“…The determination of species involved in a disease transmission is a key stone in the vector control programs, and a recurrent problem, particularly for vectors where the nymphal instars participate to the transmission of the disease, like in Chagas disease. Even in adults, the determination of the species can be delicate for example in the case of cryptic or complex of species [12,[58][59][60]. Until now, the best approach to resolve these problems is the use of molecular analysis and genetics.…”

Under pressure: phenotypic divergence and convergence associated with microhabitat adaptations in Triatominae

“…aequatorialis palms [28,72]. These bugs are much larger and darker, and have much longer heads, than typical R. ecuadoriensis, but are smaller than the closelyrelated, light-colored R. pallescens and R. colombiensis [1,73] Naked-eye phenotype differences between these northern-Andean bugs and typical southern-Andean house/nest specimens are in the range customarily associated with distinct species in the Triatominae -and tend towards the 'highly divergent' extreme of that range if we consider closely-related species within the genus Rhodnius [1,5,8,[17][18][19] (Table 1, Figs 3 and 4; S1 Text).…”

“…We reasoned that the broad ecological flexibility of R. ecuadoriensis was likely to correlate with similarly broad intraspecific variation, and set to examine the signs of diversification and adaptation in this locally important vector species. To address both macro-scale diversity and micro-scale adaptations, we analyzed mitochondrial and nuclear DNA markers that have proven useful in similar study-systems [5][6][7][8][9]11,12,[15][16][17]19,[67][68][69][70][76][77][78][79][80] and undertook a detailed qualitative/quantitative phenotypic assessment including head and forewing morphometrics [22,45,[47][48][49]81]; we then used rich, specimen-specific ecological metadata to guide the interpretation of results. We nevertheless note that our results are based on a relatively limited (albeit overall well representative) sample of geographic-ecological populations and on just two genetic loci (albeit two that are known to be informative for problems similar to the one we tackled).…”

“…Conversely, some named species have been shown to include several cryptic taxa [8]; for example, Rhodnius robustus (s.l.) is composed of at least five distinct lineages, two of which have been formally described as R. montenegrensis and R. marabaensis [8,[17][18][19][20][21].…”