Cryptic speciation in the Triatoma sordida subcomplex (Hemiptera, Reduviidae) revealed by chromosomal markers

Abstract

BackgroundChagas disease vectors (Hemiptera-Reduviidae) comprise more than 140 blood-sucking insect species of the Triatominae subfamily. The largest genus is Triatoma, subdivided in several complexes and subcomplexes according to morphology, ecology and genetic features. One of them is the sordida subcomplex, involving four species: Triatoma sordida, T. guasayana, T. garciabesi and T. patagonica. Given the great morphological similarity of these species, their taxonomic identification, evolutionary relationships and population differentiation have been controversial for many years and even today remain under discussion.MethodsWe simultaneously analyzed two chromosomal markers, C-heterochromatin distribution and 45S ribosomal genes chromosomal position, of 139 specimens from several sordida subcomplex populations from Argentina, Bolivia, Brazil and Paraguay, collected both in nature and from several established insectaries. Our results were compared with COI sequences deposited in GenBank.ResultsWe recognized five chromosomal taxa with putative hybrids, which each differ in at least one chromosome marker. Most of them present significant differences in their mtDNA sequences.ConclusionThe chromosomal taxa here show a significant chromosome differentiation involving changes in the C-heterochromatin content and in the ribosomal clusters position. This paper identifies several erroneously classified populations by morphological methods, delimits the geographical distribution of each taxon and proposes the existence of a new cryptic species, widely distributed in Argentina. We also suggest that sordida sibling species involve closely related as well as evolutionary distant species. Taxonomic status of each chromosomal taxon is discussed considering phenotypic and genetic results previously published.

Morphological and Genetic Differentiation within the Southernmost Vector of Chagas Disease: Triatoma patagonica (Hemiptera – Reduviidae)

“…sordida sensu stricto and a new putative species T . sordida Argentina (5.3%) [20], but lower than reported to separate closely related triatomine species (7.1%) [23]. Considering that the persistence of gene flow among populations is unlikely, this nucleotide divergence might be due to several causes: a recent North-South dispersion process, and/or adaptive genetic changes associated with different ecological or environmental conditions.…”

“…Although C-heterochromatin polymorphism is frequently observed in several triatomine species [18], the pronounced autosomal differences observed among North (35% of C-content) and South (0%) individuals had not been described in conspecific populations. Variations of this magnitude have only been detected among sibling Triatoma species from North [39] and South America [19,20,31]. Extensive literature describes possible effects and adaptive functions of heterochromatin on both of plants and animals [40].…”

“…Constitutive heterochromatin revealed by C-banding is a successful chromosomal marker for detection of interspecific and intraspecific variations in triatomines from different genera [18]. Significant variations in C-heterochromatin content allowed us to distinguish cryptic species in the Triatoma genus [19, 20]. DNA-based methods, particularly mitochondrial genes, have proven to be effective tools for assessing population genetics, recognition of morphologically similar species and for inferring phylogenetic relationships in Triatominae [21–24].…”

Hypothesis testing clarifies the systematics of the main Central American Chagas disease vector, Triatoma dimidiata (Latreille, 1811), across its geographic range

“…Populations may even include cryptic (morphologically identical but genetically different) species e.g. (Panzera et al, 2015). And, as closely related taxa usually share similar traits, understanding the degree of relatedness amongst different taxa allows one to predict traits.…”

Revisiting the Homoploid Hybrid Speciation Process of the Triatoma brasiliensis macromelasoma Galvão, 1956 (Hemiptera, Triatominae) Using Cytogenetic and Molecular Markers

“…1,3 Currently, there are 152 species of triatomines, distributed in 18 genera and five tribes, all species being considered as a potential vector of Chagas disease. 4,5 Although the evolutionary process in triatomine is considered as disruptive (occurs when extreme phenotypes have a fitness advantage over more intermediate phenotypes) by Dujardin et al, 6 cryptic speciation (morphologically identical populations that are reproductively isolated and successfully differentiated by molecular data) has been detected for some species (for example, Triatoma sordida [Stål, 1859] 7 and Triatoma dimidiata [Latreille, 1811] 8 ), and Costa et al 9 also suggested homoploid hybridization (derived species by hybridization without a change in chromosome number) as a possible mode of speciation in Triatominae. By means of morphometrics, 9 morphological, 9 ecological, 10 geographic, 10 isoenzymes, 11 cross-experimental, 12 and molecular analyses, 13 it was suggested that Triatoma brasiliensis macromelasoma Galvão, 1956 could be a product of hybridization between Triatoma brasiliensis Neiva, 1911 and Triatoma juazeirensis Costa and Félix, 2007. Recently, Costa et al 14 observed intermediate chromatic phenotypes for T. b. macromelasoma in various locations in areas between the T. brasiliensis and T. juazeirensis occurrences and suggested that these data, combined with molecular analysis and experimental crosses, support the distinction of a zone of hybridization (Pernambuco state, Brazil) that gave rise to the T. b. macromelasoma through homoploid evolution.…”