Chromosomal variation and genome size support existence of cryptic species of Triatoma dimidiata with different epidemiological importance as Chagas disease vectors

Abstract

Summary The wide geographical distribution of Triatoma dimidiata, one of the three major vectors of Chagas disease, ranges from Mexico to northern Peru. Since this species occupies a great diversity of artificial and natural ecotopes, its eradication is extremely difficult. In order to assist control efforts, we used chromosome analyses and DNA amount as taxonomic markers to study genetic variability in populations of T. dimidiata from Mexico, Guatemala, El Salvador and Colombia. We differentiated three groups or cytotypes defined by characteristic chromosome C‐banding patterns and genome size measured by flow cytometry. The three cytotypes are restricted to different geographic locations. Cytotype 1 occurs in Mexico (excluding Yucatán), Guatemala (excluding Petén), El Salvador and Colombia. Cytotype 2 occurs in Yucatán and cytotype 3 occurs in Petén. Cytotype 1, commonly associated with domestic and peridomestic environments but also inhabiting sylvatic ecotopes, is the most widespread and with major epidemiological significance. In contrast, the Yucatán cytotype inhabits wild ecotopes but increasingly enters houses, while the Petén cytotype appears exclusively sylvatic. We suggest that these cytotypes represent cryptic species of T. dimidiata with different epidemiological relevance as Chagas disease vectors. Poor ability to colonize human dwellings, together with their restricted geographic distribution, indicate that the Yucatán and Petén putative species probably have much less epidemiological significance than cytotype 1. Thus, the genetic markers we describe are powerful tools to differentiate cryptic species in T. dimidiata with different epidemiological significance, contributing to planning the most effective control measures.

Triatoma dimidiata in Colombia. Distribution, ecology and its epidemiological importance

“…La información genética y morfológica sugiere que T. dimidiata pudo originarse en la península de Yucatán y, desde allí, dispersarse hacia el sur y el norte del continente, diferenciándose en poblaciones relativamente discretas (20,21 …”

Genetics and evolution of triatomines: from phylogeny to vector control

“…This species presents morphologically variable populations, but early attempts to delineate geographic boundaries between them failed, and clinal variation was proposed to explain this species' extensive polymorphism (reviewed by Dorn et al, 2007). Later on however, a combination of morphology, cytogenetics and molecular data led to the unambiguous detection of a cryptic taxon and the recognition of the Dimidiata species complex (Marcilla et al, 2001;Panzera et al, 2006;Dorn et al, 2007Dorn et al, , 2009). …”

Chromosome variability in the Chagas disease vector Rhodnius pallescens (Hemiptera, Reduviidae, Rhodniini)

“…For these reasons, cytogenetics can provide useful markers for taxonomic and population analyses (Panzera et al 1995, Pérez et al 2002. Heterochromatin variation studies have allowed the identification of cryptic species in Triatoma sordida , Jurberg et al 1998 and T. dimidiata (Panzera et al 2006), as well as the detection of intra-specific variation in T. infestans (Panzera et al 2004) and Panstrongylus geniculatus (Pérez et al 2002). This chromosomal variation has been described mainly for species of Triatoma and Panstrongylus.…”

“…Cytogenetic analysis has been used to characterize more than 70 species of Triatominae (Dujardin et al 2002) and to describe chromosome variability in some species with great epidemiological importance such as Triatoma infestans (Panzera et al 2004) and Triatoma dimidiata (Panzera et al 2006). Chromosomal variation in triatomines mainly involves changes in the amount, disposition and behavior of constitutive heterochromatin.…”