Nuclear rDNA-based molecular clock of the evolution of triatominae (Hemiptera: Reduviidae), vectors of Chagas disease

Abstract

The evolutionary history and times of divergence of triatomine bug lineages are estimated from molecular clocks inferred from nucleotide sequences of the small subunit SSU (18S) and the second internal transcribed spacer Key words: Chagas disease -Triatominae vectors -nuclear rDNA -18S gene -ITS-2 spacer -molecular clockevolutionUntil the 60s, analysis of fossils was the only source of information about the time when ancestors of extant organisms lived. Since then, molecular genetic studies have provided a series of socalled molecular clocks, that may be used to estimate the evolutionary history and time of divergence of organisms. This has become particularly useful for species that have a poor fossil record, as well as for lineages of organisms which show little morphogenesis through time, or which exhibit a great deal of phenotypic variability.The molecular clock is based on the assumption that processes such as DNA replication, transcription, protein synthesis, and metabolism are similar in all organisms and that the proteins and

Biological and genetic aspects of experimental hybrids from species of the Phyllosoma complex (Hemiptera: Reduviidae: Triatominae)

“…This could be correlated with the phylogenetic proximity between these two species, which has been previously established in most related molecular studies (Bargues et al 2000, Flores et al 2001, Marcilla et al 2001, Pfeiler et al 2006 (Mazzotti & Osorio 1942, Zárate et al 1985.…”

“…On the other hand, M. longipennis appears to have a moderate degree of reproductive isolation with respect to M. mazzottii, as suggested previously (Zárate et al 1985), and a low degree in relation to M. picturatus. A possible reason may be the fact that M. longipennis and M. picturatus are phylogenetically closer to each other than M. mazzottii is to any of the other studied species (Bargues et al 2000, Flores et al 2001, Marcilla et al 2001. Another reason is the existence of a correlation between geographic distance and degree of reproductive isolation, since the species that have been collected parapatrically in various areas, such as M. longipennis and M. picturatus (Martínez-Ibarra et al 2001, 2008, Magallón-Gastélum 2006, M. pallidipennis and M. longipennis, and M. pallidipennis and M. picturatus, presented lower degrees of reproductive isolation (Martínez-Ibarra et al 2005).…”

“…More recently, Martínez-Ibarra et al (2005) have reported natural fertile hybrids from M. pallidipennis and M. longipennis as well as from M. pallidipennis and M. picturatus in the wild, establishing a low degree of reproductive isolation among these three species of the genus Meccus. These studies, showing biological evidence for the low degree of reproductive isolation among these four species of the genus Meccus, have been enhanced by recent molecular studies (Bargues et al 2000, Marcilla et al 2001) that support the proposition that six species of the Phyllosoma complex (including M. phyllosomus and M. bassolsae) should be considered as subspecies. On the other hand, other molecular studies (Sainz et al 2004, Pfeiler et al 2006) consider these species as valid ones.…”

Occurrence of hybrids and laboratory evidence of fertility among three species of the Phyllosoma complex (Hemiptera: Reduviidae) in Mexico

“…This assumption is supported by some molecular studies on the species of the Phyllosoma complex, in which it was established that the genetic differences between those taxa (species) are so small (sometimes even none at all) that there is no support to maintain them as separate species (Bargues et al 2008). Furthermore, their divergence is estimated at only 0.74-2.28 Mya by the rDNA molecular clock, which also seems consistent with the subspecific rank (Bargues et al 2000). Moreover, ITS-2 and CytB markers and the use of antennal phenotype studies have always reached the same conclusion (Marcilla et al 2001, Bargues et al 2002, 2010.…”

“…Since then, an argument about their proper taxonomic rank has developed. Even though some researchers have considered some of these species as subspecies (Espinoza-Gómez et al 2002), most have considered them as species until recently, when molecular evidence led once again to the proposal [as Mazzotti & Osorio (1942) did] to consider them as subspecies of M. phyllosomus (Bargues et al 2000, Marcilla et al 2001, 2010. However, even though that molecular evidence seems to be forceful, biological evidence is still incomplete because conclusions from some of those previously carried out studies have been based on null or a small number of crosses among the species of the Phyllosoma complex (Mazzotti & Osorio 1942, Mazzotti 1943, Usinger et al 1966.…”