New arrangements on several species subcomplexes of Triatoma genus based on the chromosomal position of ribosomal genes (Hemiptera - Triatominae).

The hemipteran subfamily Triatominae includes 150 blood-sucking species, vectors of Chagas disease. By far the most specious genus is Triatoma, assembled in groups, complexes and subcomplexes based on morphological similarities, geographic distribution and genetic data. However, many molecular studies questioned the species integration of several subcomplexes as monophyletic units. In triatomines, chromosomal position of major ribosomal DNA (rDNA) loci is extremely variable but seems to be species-specific and an evolutionary conserved genetic trait, so that closely related species tend to have ribosomal clusters in the same chromosomal location. Considering that the autosomal position as the ancestral character for all heteropteran species, including triatomines, we suggest that the movement of rDNA loci from autosomes to sex chromosomes rapidly established reproductive barriers between divergent lineages. We proposed that the rDNA translocation from the autosomes to the sex chromosomes restrict reproductive compatibility and eventually promote speciation processes. We analyzed the chromosomal position of 45S rDNA clusters in almost all species of the matogrossensis, rubrovaria, maculata and sordida subcomplexes. The fluorescent in situ hybridization results are discussed considering the available genetic data and we proposed new arrangements in the species that constitute each one of these subcomplexes.

Would Nesotriatoma bruneri Usinger, 1944 be a valid species?

Variation in the size and morphological differences intraspecific of Nesotriatoma flavida led to the description of N. bruneri. However, two years later the same author proposed the synonymization N. bruneri with N. flavida. N. bruneri was revalidated through morphological analysis after 35 years. Thus, given the existing taxonomic questioning between these Cuban triatomines, we analyzed new parameters such as genetic distance from the mitochondrial 16S rDNA deposited in Genbank and cytogenetic characterization, through the constitutive heterochromatin pattern, in order to reassess the specific status of N. bruneri. The analysis of the disposition of constitutive heterochromatin in the genome of these triatomines allowed observing that only the sex chromosome Y is heterochromatic, and the autosomes and the sex chromosomes X are euchromatic. These characteristics are identical to those described for N. flavida. By means of analysis of genetic distance matrix, we found that the genetic distance between N. bruneri and N. flavida was only 0.04%. Thus, by means of extremely low genetic distance and identical cytogenetic characteristics, we suggest that N. bruneri should be back again synonymized with N. flavida. However, we recommend that experimental hybrid crosses and new molecular analysis should be conducted, focusing mainly in the genetic distance based on other genes, on the rate of fertility of eggs and viability of hybrids to confirm the proposed of synonymization.