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

Abstract

The epidemiological importance of Chagas disease vectors largely depends on their spreading ability and adaptation to domestic habitats. Triatoma patagonica is a secondary vector of Chagas disease endemic of Argentina, and it has been found colonizing domiciles and most commonly peridomiciliary structures in several Argentine provinces and morphological variation along its distribution range have been described. To asses if population differentiation represents geographic variants or true biological species, multiple genetic and phenotypic approaches and laboratory cross-breeding were performed in T. patagonica peridomestic populations. Analyses of chromatic variation of forewings, their size and the content of C-heterochromatin on chromosomes revealed that populations are structured following a North-South latitudinal variation. Cytochrome c oxidase I mitochondrial gene (COI) nucleotide analysis showed a mean genetic distance of 5.2% between the most distant populations. The cross-breeding experiments suggest a partial reproductive isolation between some populations with 40% of couples not laying eggs and low hatching efficiency. Our findings reveal phenotypic and genetic variations that suggest an incipient differentiation processes among T. patagonica populations with a pronounced phenotypic and genetic divergence between the most distant populations. The population differentiation here reported is probably related to differential environmental conditions and it could reflect the occurrence of an incipient speciation process in T. patagonica.

Phenotypic and genetic variation of Triatoma costalimai (Hemiptera: Reduviidae)

“…Triatomines have high morphological plasticity and closely related species develop rapid morphological variations as they adapt to different environments 13 . We suggest that the connexivum color patterns are related to environmental conditions where the triatomines were collected from, and this has been previously observed in T. patagonica 14 . Wing morphometry also revealed differences within T. costalimai populations and between T. jatai and T. costalimai 4 .…”

Morphometric variability among the species of the Sordida subcomplex (Hemiptera: Reduviidae: Triatominae): evidence for differentiation across the distribution range of Triatoma sordida

“…Moreover, T. sordida cuticular hydrocarbon composition exhibits a heterogeneous pattern, suggesting that it should not be considered a single species [ 48 ]. Nevertheless, molecular divergence between T. sordida from Argentina and T. sordida from Brazil was only 5.3% [ 7 ], a similar value to that distinguishing subspecies of Triatoma sanguisuga (Le Conte, 1855) [ 53 ] and distant populations of T. patagonica [ 52 ].…”

“…Moreover, body size and the pattern of connexivum variation seem to be different (Fig. 2a ), although these characters may vary across populations as well as in other species of the Triatominae [ 52 ]. In another morphogeometric study of two Brazilian and one Argentine population of T. sordida and one population of T. garciabesi , the specimens of T. garciabesi and Brazilian T. sordida were well separated using head and wing shape whereas the Argentine population of T. sordida overlapped for wing and head shape with Brazilian T. sordida and with T. garciabesi [ 21 ].…”

A new species of Rhodnius from Brazil (Hemiptera, Reduviidae, Triatominae)

“…The technique proved valid, for instance, to indicate the distinction between Mepraia spinolai and M. gajardoi ; T. bahiensis and T. lenti ; R. colombiensis , R. ecuadoriensis and R. pallescens ; five populations of T. patagonica (Campos et al 2011, Díaz et al 2014, Nattero et al 2016). However, even though that technique has contributed to distinguish even very close species, it showed no significant results to distinguish R. taquarussuensis sp.…”