ITS Haplotypes Research Articles

Origin and phylogeography of the Chagas disease main vector Triatoma infestans based on nuclear rDNA sequences and genome size

For about half of all Chagas disease cases T. infestans has been the responsible vector. Contributing to its genetic knowledge will increase our understanding of the capacity of geographic expansion and domiciliation of triatomines. Populations of all infestans subcomplex species, T. infestans, T. delpontei, T. platensis and T. melanosoma and the so-called T. infestans “dark morph”, from many South American countries were studied. A total of 10 and 7 different ITS-2 and ITS-1 haplotypes, respectively, were found. The total intraspecific ITS-2 nucleotide variability detected in T. infestans is the highest hitherto known in triatomines. ITS-1 minisatellites, detected for the first time in triatomines, proved to be homologous and thus become useful markers. Calculations show that ITS-1 evolves 1.12–2.60 times faster than ITS-2. Despite all species analyzed presenting the same n = 22 chromosome number, a large variation of the haploid DNA content was found, including a strikingly high DNA content difference between Andean and non-Andean specimens of T. infestans (mean reduction of 30%, with a maximum of up to 40%) and a correlation between presence/absence of minisatellites and larger/smaller genome size. Population genetics analysis of the eight composite haplotypes of T. infestans and net differences corroborate that there are clear differences between western and eastern populations (60%), and little genetic variation among populations (1.3%) and within populations (40%) within these two groups with migration rates larger than one individual per generation corresponding only to pairs of populations one from each of these groups. These values are indicative either of a large enough gene flow to prevent population differentiation by drift within each geographic area or a very recent spread, the latter hypothesis fitting available data better. Phylogenetic trees support a common ancestor for T. infestans and T. platensis, an origin of T. infestans in Bolivian highlands and two different dispersal lines, one throughout Andean regions of Bolivia and Peru and another in non-Andean lowlands of Chile, Paraguay, Argentina, Uruguay and Brazil.

Molecular evidence supports the distinction between Xanthoria parietina and X. aureola (Teloschistaceae, lichenized Ascomycota)

This study aims to clarify taxonomic relationships within the current concept of Xanthoria parietina in northern Europe. For comparison, X. calcicola was also included in the study. Morphological as well as molecular data were utilized. Morphology indicated the presence of three species, Xanthoria parietina, X. calcicola, and X. aureola, the latter of which is resurrected here from synonymy. The most important separating characters involve colour and thickness of the thallus, lobe width, morphology of laminar structures, and the texture of the upper surface. X. aureola, as recognized here, mostly occurs on seashore rocks. Part of the IGS region as well as the complete ITS were sequenced in 70 individual thalli representing ten geographical regions in Europe. In total, 19 different IGS haplotypes and 20 different ITS haplotypes were present in the data set. Owing to indications of possible recombination between the IGS and the ITS, the two data sets were analyzed separately. Haplotype networks were estimated, both of which indicate that X. parietina is distinct from X. aureola and X. calcicola. In our sample, the two latter do not share haplotypes, but are only separated by a few mutational steps.