Morphometric and genetic characterization as tools for selection of Apis mellifera (Hymenoptera: Apidae) stocks in an area of natural hybridization in Argentina.

Beekeepers around the world select bees' characteristics that facilitate and favor production. In regions where hybridization among lineages is taking place, this selection is a challenge, given that these regions are "natural laboratories", where the action of evolutionary processes of a population or species occurs in real time. A natural honeybee (Apis mellifera) hybrid zone exists in Argentina between 28° and 35° South, where Africanized (AHB) and European (EHB) populations converge. In this zone, beekeepers use selected genetic resources of European origin mostly, since the local Africanized bees show a higher defensive behavior, which is not desirable for management. Although EHB colonies have many advantages for honey production, they are not fully adapted to the subtropical climate and are susceptible to certain parasitosis such as varroosis. In addition, both AHB and EHB mate in drone congregation areas (DCAs), where males and virgin queens fly to meet, resulting in variability in the desired characteristics. In this study, we explored the degree of hybridization within a DCA and its reference apiary, located in the province of Entre Ríos, by applying two complementary techniques. First, morphotypes with different degrees of hybridization between European and African subspecies were observed in the reference apiary, indicating a high sensitivity of this morphometric approach to detect hybridization in these populations. Second, a genetic analysis revealed haplotypes of both origins for drones in DCAs, with a higher prevalence of European haplotypes, while all the colonies from the reference apiary exhibited European haplotypes. Overall, our results are in line with the strong impact that commercial beekeeping has on the genetics of DCAs. We show how wing morphometry may be used to monitor hybridization between European and African subspecies, a tool that may be evaluated in other regions of the world where hybridization occurs.

Gut Bacteriome Analysis of Anastrepha fraterculus sp. 1 During the Early Steps of Laboratory Colonization.

Microbial communities associated to insect species are involved in essential biological functions such as host nutrition, reproduction and survivability. Main factors have been described as modulators of gut bacterial community, such as diet, habit, developmental stage and taxonomy of the host. The present work focuses on the complex changes that gut microbial communities go through when wild insects are introduced to artificial rearing conditions. Specifically, we analyzed the effect of the laboratory colonization on the richness and diversity of the gut bacteriome hosted by the fruit fly pest Anastrepha fraterculus sp. 1. Bacterial profiles were studied by amplicon sequencing of the 16S rRNA V3-V4 hypervariable region in gut samples of males and females, in teneral (1-day-old, unfed) and post-teneral (15-day-old, fed) flies. A total of 3,147,665 sequence reads were obtained and 32 bacterial operational taxonomic units (OTUs) were identified. Proteobacteria was the most abundant phylum (93.3% of the total reads) and, Wolbachia and Enterobacter were the most represented taxa at the genus level (29.9% and 27.7%, respectively, of the total read counts). Wild and laboratory flies showed highly significant differences in the relative abundances of bacteria. The analysis of the core bacteriome showed the presence of five OTUs in all samples grouped by origin, while nine and five OTUs were exclusively detected in laboratory and wild flies, respectively. Irrespective of fly origin or sex, a dominant presence of Wolbachia was observed in teneral flies, whereas Enterobacter was highly abundant in post-teneral individuals. We evidenced significant differences in bacterial richness and diversity among generations under laboratory colonization (F0, F1, F3 and F6) and compared to laboratory and wild flies, displaying also differential patterns between teneral and post-teneral flies. Laboratory and wild A. fraterculus sp. 1 harbor different gut bacterial communities. Laboratory colonization has an important effect on the microbiota, most likely associated to the combined effects of insect physiology and environmental conditions (e.g., diet and colony management).

Genetic variation and heteroplasmy of Varroa destructor inferred from ND4 mtDNA sequences.

Varroa destructor, a parasitic mite of the western honey bee, Apis mellifera L., is a serious threat to colonies and beekeeping worldwide. Population genetics studies of the mite have provided information on two mitochondrial haplotypes infecting honey bee colonies, named K and J (after Korea and Japan, respectively, where they were originally identified). On the American continent, the K haplotype is much more prevalent, with the J haplotype only detected in some areas of Brazil. The aims of the present study were to assess the genetic diversity of V. destructor populations in the major beekeeping region of Argentina and to evaluate the presence of heteroplasmy at the nucleotide level. Phoretic mites were collected from managed A. mellifera colonies in ten localities, and four mitochondrial DNA (mtDNA) regions (COXI, ND4, ND4L, and ND5) were analyzed. Based on cytochrome oxidase subunit I (COXI) sequencing, exclusively the K haplotype of V. destructor was detected. Furthermore, two sub-haplotypes (KArg-N1 and KArg-N2) were identified from a variation in ND4 sequences and the frequency of these sub-haplotypes was found to significantly correlate with geographical latitude. The occurrence of site heteroplasmy was also evident for this gene. Therefore, ND4 appears to be a sensitive marker for detecting genetic variability in mite populations. Site heteroplasmy emerges as a phenomenon that could be relatively frequent in V. destructor.

Distribution and prevalence of Nosema apis and N. ceranae in temperate and subtropical eco-regions of Argentina.

A total of 361 colonies from 59 apiaries located in two temperate and three subtropical eco-regions were examined during the post-harvest period to determine distribution and prevalence of Nosema spp. Apiaries from subtropical eco-regions showed a lower spore count than those from temperate eco-regions. Pure N. ceranae and co-infection were detected in apiaries from all regions. In contrast, pure N. apis infection was exclusively observed in the subtropical study region. The predominant detection of N. apis in a subtropical region joining a southern temperate region where mainly co-infected apiaries were identified is in contrast to previous reports.