Phylogeography and Genetic Variation of Triatoma dimidiata, the Main Chagas Disease Vector in Central America, and Its Position within the Genus Triatoma

Abstract

BackgroundAmong Chagas disease triatomine vectors, the largest genus, Triatoma, includes species of high public health interest. Triatoma dimidiata, the main vector throughout Central America and up to Ecuador, presents extensive phenotypic, genotypic, and behavioral diversity in sylvatic, peridomestic and domestic habitats, and non-domiciliated populations acting as reinfestation sources. DNA sequence analyses, phylogenetic reconstruction methods, and genetic variation approaches are combined to investigate the haplotype profiling, genetic polymorphism, phylogeography, and evolutionary trends of T. dimidiata and its closest relatives within Triatoma. This is the largest interpopulational analysis performed on a triatomine species so far.Methodology and FindingsTriatomines from Mexico, Guatemala, Honduras, Nicaragua, Panama, Cuba, Colombia, Ecuador, and Brazil were used. Triatoma dimidiata populations follow different evolutionary divergences in which geographical isolation appears to have had an important influence. A southern Mexican–northern Guatemalan ancestral form gave rise to two main clades. One clade remained confined to the Yucatan peninsula and northern parts of Chiapas State, Guatemala, and Honduras, with extant descendants deserving specific status. Within the second clade, extant subspecies diversity was shaped by adaptive radiation derived from Guatemalan ancestral populations. Central American populations correspond to subspecies T. d. dimidiata. A southern spread into Panama and Colombia gave the T. d. capitata forms, and a northwestern spread rising from Guatemala into Mexico gave the T. d. maculipennis forms. Triatoma hegneri appears as a subspecific insular form.ConclusionsThe comparison with very numerous Triatoma species allows us to reach highly supported conclusions not only about T. dimidiata, but also on different, important Triatoma species groupings and their evolution. The very large intraspecific genetic variability found in T. dimidiata sensu lato has never been detected in a triatomine species before. The distinction between the five different taxa furnishes a new frame for future analyses of the different vector transmission capacities and epidemiological characteristics of Chagas disease. Results indicate that T. dimidiata will offer problems for control, although dwelling insecticide spraying might be successful against introduced populations in Ecuador.

Biological and genetic aspects of crosses between species of the genus Meccus (Hemiptera: Reduviidae Triatominae)

“…However, "subspecies are local populations that are recognisably different from each other but they are nevertheless considered to belong to the same species, because they are observed to interbreed in nature or because it is inferred that they are likely to interbreed" (Mayr & Diamond 2001). In accordance with these species and subspecies concepts and in light of some previously published reports (Flores et al 2001, Martínez et al 2005, Takashi-Obara et al 2007, Bargues et al 2008, the biological evidence reported here supports the proposition that it is more appropriate to attribute a subspecies level to M. bassolsae, as has been proposed for M. pallidipen nis, M. longipennis and M. picturatus (Martínez-Ibarra et al 2008b). However, the same biological evidence supports the proposal that M. phyllosomus is a full spe cies, as some recent molecular studies have proposed (Sainz et al 2004, Pfeiler et al 2006.…”

“…These results are in agreement with a previous study (Martínez-Ibarra et al 2008b), where M. mazzottii was reproductively isolated from the four species of Meccus examined (M. phyllosomus was not included in that study). Our results, in combination with results showing little or no genetic differences between these species (Bargues et al 2008) indicate that these species are closely related and have diverged very recently.…”

“…A discussion regarding the proper taxonomic assignment of these species of the genus Meccus (species or subspecies) has been ongoing for a number of years (Mazzotti & Osorio 1942, Lent & Wygodzinsky 1979. Biological and molecular studies on typical specimens (Mazzotti & Osorio 1942, Bargues et al 2008, Martínez-Ibarra et al 2008b) and on the naturally crossbred descendents of different individuals from sympatric populations (M. pallidipennis, M. longipennis and M. picturatus) (Martínez-Ibarra et al 2009) have lead to a proposal to reclassify some (M. pallidipennis, M. longipennis and M. picturatus) (Marcilla et al 2001, Martínez-Ibarra et al 2008b or all (Bargues et al 2008 of the six species of the genus Meccus to subspecies of M. phyllosomus. Other molecular and biological studies support the consideration of these groups as full species (Sainz et al 2004, Pfeiler et al 2006, Martínez-Ibarra et al 2008b).…”

“…Other molecular and biological studies support the consideration of these groups as full species (Sainz et al 2004, Pfeiler et al 2006, Martínez-Ibarra et al 2008b). However, molecular evidence (Bargues et al 2008) supports the revalidation of the genus Meccus for the six species traditionally grouped into the Phyllosoma complex (Carcavallo et al 2000).…”

Ciclo de vida de Triatoma dimidiata Latreille, 1811 (Hemiptera, Reduviidae) en condiciones de laboratorio: producción de ninfas para ensayos biológicos

“…Las diferencias observadas en los rangos y en el tiempo medio de duración del ciclo de vida de la cepa colombiana utilizada en este estudio con respecto otras cepas de Centroamérica y Colombia, pueden deberse a las condiciones previas al ensayo, como el tiempo de colonización en el laboratorio; a variaciones de las condiciones del laboratorio en el ensayo, o a diferencias de taxonomía numérica (phenetics) y genéticas de la población ya demostradas para esta especie (32)(33)(34).…”