The cotton bollworm, Helicoverpa armigera (Hübner), was recently introduced in Brazil. During the 2012-2013 harvest, producers reported reduced yields up to 35% on major crops. The economic losses reached US$ 1 billion only in western Bahia, triggering a phytosanitary crisis. The deficiencies in existing taxonomic keys to deal with the morphologically indistinct larvae of H. armigera and the native Helicoverpa zea (Boddie) constrained the detection of new incursions of this heliothine invader. This study explored the identity of heliothine larvae that were found infesting soybean- and corn-growing areas from Roraima state, northern Brazil, through sequences of the mitochondrial cytochrome c oxidase subunit I gene. The inter- and intraspecies sequence variations of DNA barcodes in H. armigera and H. zea were analyzed. The genetic diversity and population structure of the specimens from Roraima and two populations from Piauí and Bahia states, northeastern Brazil, were assessed by adding the cytochrome c oxidase subunit II gene to the analysis. Owing to the lack of studies on genetic introgression for the two species, the suitability of using three different nuclear genes to distinguish the two species was also investigated. The results showed strong evidence that the heliothine larvae from north and northeast of Brazil are conspecific with H. armigera, suggesting that this invasive moth has already crossed the Amazon basin. Surveys in the north of South America should start as soon as possible to monitor the entry or spread of this moth in the Caribbean, Central America, and the United States.

Livestock production is an important economic activity in Brazil, which has been suffering significant losses due to the impact of parasites. The New World screwworm (NWS) fly, Cochliomyia hominivorax, is an ectoparasite and one of the most important myiasis-causing flies endemic to the Americas. The geographic distribution of NWS has been reduced after the implementation of the Sterile Insect Technique (SIT), being eradicated in North America and part of Central America. In South America, C. hominivorax is controlled by chemical insecticides, although indiscriminate use can cause selection of resistant individuals. Previous studies have associated the Gly137Asp and Trp251Leu mutations in the active site of carboxylesterase E3 to resistance of diethyl and dimethyl-organophosphates insecticides, respectively. Here, we have sequenced a fragment of the carboxylesterase E3 gene (ChαE7), comprising part of intron iII, exon eIII, intron iIII and part of exon eIV, and three mitochondrial gene sequences (CR, COI and COII), of NWS flies from 21 locations in South America. These markers were used for population structure analyses and the ChαE7 gene was also investigated to gain insight into the selective pressures that have shaped its evolution. Analysis of molecular variance (AMOVA) and pairwise FST analysis indicated an increased genetic structure between locations in the ChαE7 compared to the concatenated mitochondrial genes. Discriminant analysis of principal components (DAPC) and spatial analysis of molecular variance (SAMOVA) indicated different degrees of genetic structure for all markers, in agreement with the AMOVA results, but with low correlation to geographic data. The NWS fly is considered a panmitic species based on mitochondrial data, while it is structured into three groups considering the ChαE7 gene. A negative association between the two mutations related to organophosphate resistance and Fay & Wu’s H significant negative values for the exons, suggest that these mutations evolved under positive selection.

The New World screwworm fly Cochliomyia hominivorax (Coquerel, 1858) (Diptera: Calliphoridae) is an important livestock pest endemic to the Americas that has been eradicated from North and continental Central America with a control program based on the Sterile Insect Technique (SIT). The establishment of target management units is a strategic step in the implementation of new control programs, which can be achieved using genetic studies of natural populations. Previous studies of New World screwworm fly populations were conducted on the continental scale and identified four main groups: two in South America and two in the Caribbean. However, studies within these groups are needed to determine which smaller geographic areas can be treated as management units. Here, we analyze the genetic variability distribution and the population demographic signals of the New World screwworm fly in a 6,000 km2 area located along the border of Brazil and Uruguay. This area was the subject of the first control pilot program conducted in South America. We studied eight microsatellite loci and sequences from two mitochondrial DNA regions in individuals sampled at 20-25 livestock breeding farms. We observed no population structure and found high genetic variability on the geographical scale sampled for both molecular markers. Our microsatellite data suggest that these populations are not in equilibrium, and demographic analyses based on mitochondrial data indicate population expansion. These results suggest that this geographic scale is not adequate for future New World screwworm fly management in South America.

The New World screwworm (NWS) fly, Cochliomyia hominivorax (Diptera: Calliphoridae), is an economically important ectoparasite currently distributed in South America and in the Caribbean basin. The successful eradication of this species in USA, Mexico and continental Central America was achieved by a control program based on the sterile insect technique (SIT). In order to implement a genetic control strategy over the NWS fly’s current area of occurrence, first, it is necessary to understand the species dynamics and population structure. In order to address this objective, the spatial genetic structure of the NWS fly was previously reported in South America based on different genetic markers; however, to date, no study has investigated temporal changes in the genetic composition of its populations. In the current study, the temporal genetic structure of a NWS fly population from Uruguay was investigated through two consecutive samplings from the same locality over an interval of approximately 18 generations. The genetic structure was accessed with neutral and under selection SNPs obtained with genotyping-by-sequencing. The results gathered with these data were compared to estimates achieved with mitochondrial DNA sequences and eight microsatellite markers. Temporal changes in the genetic composition were revealed by all three molecular markers, which may be attributed to seasonal changes in the NWS fly’s southern distribution. SNPs were employed for the first time for estimating the genetic structure in a NWS fly population; these results provide new clues and perspectives on its population genetic structure. This approach could have significant implications for the planning and implementation of management programs.

Mitonuclear discordance has been widely reported in animal species. In stingless bees, the occurrence of mitonuclear discordance is favoured by the adopted colony-founding strategy [dependent colony foundation (DCF)], with phylopatric females and dispersing males. To address the extent to which the DCF system is reflected in the population structure of Partamona helleri, a stingless bee found in Brazilian Atlantic Forest, we sampled for sequences of maternally heritable mitochondrial DNA (mtDNA) and biparentally inherited nuclear microsatellite markers in workers from 339 colonies, covering its entire distribution range. We found evidence of mitonuclear discordance in P. helleri, which is compatible with the DCF strategy. Genetic structuring of the mtDNA was associated with the occupation of an area by few female lineages, and genetic structuring of the nuclear DNA was associated with isolation by distance. Phylogeographical analysis showed that the origin of P. helleri seems to have been in the region of the state of Bahia 860 000 years ago and that the divergence between the lineages began 520 000 years ago. From this primary centre of dispersal, a main north-to-south migration route occurred, resulting in the occupation of areas in the southern portion of the Atlantic Forest, probably favoured by the dynamics of evergreen forest expansions during the Quaternary.