The European honeybee, Apis mellifera L. (Hymenoptera: Apidae), is considered as a main contributor to pollination of important crops and to honey production. Originally, beekeeping in Argentina was performed in an extended area covering the north and central region of the country and involving A. mellifera of European origin. Later, honeybees of African origin entered South America through Brazil and hybridized with European genetic resources, giving rise to Africanized populations that are characterized by a more aggressive behavior among other unfavorable traits. In this study, a genetic characterization of 396 honeybee colonies from the most important apicultural region of Argentina is presented in order to provide an updated description of population structure and genetic diversity of commercial and feral colonies. Diversity was analyzed using mitochondrial (COI-COII region) and nuclear (eight microsatellites) markers. Three European (M4, C1, C2J) and three African (A1, A4, A30) haplotypes were detected. European haplotypes were mostly found in commercial apiaries, whereas African haplotypes were detected at high frequencies in feral colonies. Microsatellite data were analyzed to estimate population genetic variability at the province level and to evaluate genetic admixture. A high level of hybridization between Africanized and European honeybees was detected with a significant latitudinal cline from north to south. Extensive population admixture resulted in the definition of four clusters that included both feral and commercial colonies and that are explained not only by geographical distribution and degree of Africanization but also by human influence through beekeeping activities.

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BackgroundThe interaction between gut bacterial symbionts and Tephritidae became the focus of several studies that showed that bacteria contributed to the nutritional status and the reproductive potential of its fruit fly hosts. Anastrepha fraterculus is an economically important fruit pest in South America. This pest is currently controlled by insecticides, which prompt the development of environmentally friendly methods such as the sterile insect technique (SIT). For SIT to be effective, a deep understanding of the biology and sexual behavior of the target species is needed. Although many studies have contributed in this direction, little is known about the composition and role of A. fraterculus symbiotic bacteria. In this study we tested the hypothesis that gut bacteria contribute to nutritional status and reproductive success of A. fraterculus males.ResultsAB affected the bacterial community of the digestive tract of A. fraterculus, in particular bacteria belonging to the Enterobacteriaceae family, which was the dominant bacterial group in the control flies (i.e., non-treated with AB). AB negatively affected parameters directly related to the mating success of laboratory males and their nutritional status. AB also affected males’ survival under starvation conditions. The effect of AB on the behaviour and nutritional status of the males depended on two additional factors: the origin of the males and the presence of a proteinaceous source in the diet.ConclusionsOur results suggest that A. fraterculus males gut contain symbiotic organisms that are able to exert a positive contribution on A. fraterculus males’ fitness, although the physiological mechanisms still need further studies.

BackgroundWolbachia, one of the most abundant taxa of intracellular Alphaproteobacteria, is widespread among arthropods and filarial nematodes. The presence of these maternally inherited bacteria is associated with modifications of host fitness, including a variety of reproductive abnormalities, such as cytoplasmic incompatibility, thelytokous parthenogenesis, host feminization and male-killing. Wolbachia has attracted much interest for its role in biological, ecological and evolutionary processes as well as for its potential use in novel and environmentally-friendly strategies for the control of insect pests and disease vectors including a major agricultural pest, the South American fruit fly, Anastrepha fraterculus Wiedemann (Diptera: Tephritidae).ResultsWe used wsp, 16S rRNA and a multilocus sequence typing (MLST) scheme including gatB, coxA, hcpA, fbpA, and ftsZ genes to detect and characterize the Wolbachia infection in laboratory strains and wild populations of A. fraterculus from Argentina. Wolbachia was found in all A. fraterculus individuals studied. Nucleotide sequences analysis of wsp gene allowed the identification of two Wolbachia nucleotide variants (named wAfraCast1_A and wAfraCast2_A). After the analysis of 76 individuals, a high prevalence of the wAfraCast2_A variant was found both, in laboratory (82%) and wild populations (95%). MLST analysis identified both Wolbachia genetic variants as sequence type 13. Phylogenetic analysis of concatenated MLST datasets clustered wAfraCast1/2_A in the supergroup A. Paired-crossing experiments among single infected laboratory strains showed a phenotype specifically associated to wAfraCast1_A that includes slight detrimental effects on larval survival, a female-biased sex ratio; suggesting the induction of male-killing phenomena, and a decreased proportion of females producing descendants that appears attributable to the lack of sperm in their spermathecae.ConclusionsWe detected and characterized at the molecular level two wsp gene sequence variants of Wolbachia both in laboratory and wild populations of A. fraterculus sp.1 from Argentina. Crossing experiments on singly-infected A. fraterculus strains showed evidence of a male killing-like mechanism potentially associated to the wAfraCast1_A - A. fraterculus interactions. Further mating experiments including antibiotic treatments and the analysis of early and late immature stages of descendants will contribute to our understanding of the phenotypes elicited by the Wolbachia variant wAfraCast1_A in A. fraterculus sp.1.

The South American fruit fly, Anastrepha fraterculus, is clearly undergoing a speciation process. Among others, two of their morphotypes, the Brazilian-1 and Peruvian, have accumulated differences in pre- and post-zygotic mechanisms resulting in a degree of reproductive isolation. Both harbor a different strain of Wolbachia, which is a widespread endosymbiotic bacterium among many invertebrates producing a range of reproductive effects. In this paper, we studied the role of this bacterium as one of the factors involved in such isolation process. Infected and cured laboratory colonies were used to test pre- and post-zygotic effects, with special emphasis in uni- and bi-directional cytoplasmic incompatibility (CI). We showed that Wolbachia is the only known reproductive symbiont present in these morphotypes. Wolbachia reduced the ability for embryonic development in crosses involving cured females and infected males within each morphotype (uni-directional CI). This inhibition showed to be more effective in the Peruvian morphotype. Bi-directional CI was not evidenced, suggesting the presence of compatible Wolbachia strains. We conclude that Wolbachia is not directly involved in the speciation process of these morphotypes. Other mechanisms rather than CI should be explored in order to explain the reduced mating compatibility between the Brazilian-1 and Peruvian morphotypes.

2012) Rearing of the fruit fly parasitoid Diachasmimorpha longicaudata (Hymenoptera: Braconidae) on X-ray irradiated larvae of Ceratitis capitata (Diptera: Tephritidae), We evaluated the effects of X-ray irradiation on larvae of Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), with the aim of finding a treatment that prevented adult fly emergence, yet did not adversely affect larval quality as rearing hosts for the parasitoid Diachasmimorpha longicaudata (Ashmead) (Hymenoptera: Ichneumonidae). Two experiments were carried out. In the first experiment, small numbers of larvae were held in Petri dishes with and without small amounts of rearing media and then irradiated with doses of X-rays ranging from 0 to 8333.6 R (equivalent to 80 Gy). In the second experiment, higher numbers of larvae were held in a manner resembling mass-rearing conditions, and were then irradiated with X-rays ranging from 0 to 10,417 R (equivalent to 100 Gy). In both experiments, the only factor that significantly affected fly emergence was irradiation of larvae. Fly emergence decreased markedly as the irradiation dose increased, and complete suppression of fly emergence was achieved at 6250.2 R (equivalent to 60 Gy) when larvae were irradiated in small batches with or without rearing media. Irradiation also affected the fertility of those flies that did emerge following treatment. In the second experiment, we found the parasitoids reared from irradiated larvae produced a higher parasitism rate and a higher number of female offspring than did parasitoids reared from control (nonirradiated) larvae. Mean fecundity of F1 parasitoids reared from irradiated larvae were affected positively by irradiation only at the 8333.6 R (80 Gy) dose. Our results show that X-ray irradiation can be used to inhibit fruit fly adult emergence and that irradiated larvae are at least as good a rearing substrate as nonirradiated larvae. Future studies should focus on the adjustment of our findings to a mass-rearing scale.

23hominivorax Coquerel); several species of tsetse fly (Glossina spp.); and the codling 71 moth (Cydia pomonella L.) [reviewed in 17, 18]. 72 73 Successful SIT programs as part of Area-wide Integrated Pest Management (IPM) 74 strategies have also been implemented for several tephritids: Ceratitis capitata 75 Wiedemann; Anastrepha ludens Loew; Anastrepha obliqua Macquart; Anastrepha 76 fraterculus Wiedemann; Zeugodacus cucurbitae Coquillett; Bactrocera dorsalis Hendel; 77and Bactrocera tryoni Froggatt [6, 12, 13, 15]. SIT is currently being developed for two 78 additional tephritid species: Dacus ciliatus Loew and Bactrocera tau Walker [19, 20]. 79The advantages of the SIT over other pest control approaches (e.g. use of pesticides) 80 are that it is the most environmentally friendly and resistance is unlikely to evolve [21, 81 22]. 82 83 Another autocidal strategy where mating between mass-reared and wild insects can be 84 used to suppress pest populations is the incompatible insect technique (IIT). IIT also 85 relies on the principle of reducing female fertility, but utilizes endosymbiotic bacteria 86 instead of radiation, to induce a context-dependent sterility in wild females. It is based 87 on the ability of certain maternally inherited bacteria (namely from the genus Wolbachia) 88to induce a form of reproductive incompatibility known as cytoplasmic incompatibility (CI; 89 explained in the section below). Herein we review the current knowledge on taxonomic 90 diversity of Wolbachia-tephritid associations and their phenotypic consequences, and 91 identify gaps in knowledge and approaches in the context of potential application of IIT in 92 AW-IPM programs to control tephritid pests. We also discuss scenarios where these 93 two autocidal strategies, SIT and IIT, could be potentially combined for the population 94 suppression of tephritid pests. 95 96 5 The influence of Wolbachia on host ecology 97Insects and other arthropods are common hosts of maternally inherited bacteria 98 [reviewed in 23]. These heritable endosymbionts can have a strong influence on host 99 ecology. Such vertically transmitted bacteria are typically vastly (or fully) dependent on 100 the host for survival and transmission. Certain associations are obligate for both 101 partners, and generally involve a nutritional benefit to the host. Other heritable bacteria 102 are facultative, with such associations ranging from mutualistic to parasitic from the 103 host's perspective. Among these, Wolbachia is the most common and widespread 104 facultative symbiont of insects and arthropods [24][25][26][27]. 105 106 Wolbachia is a diverse and old genus [possibly older than 200 million years; 28] of 107 intracellular gram-negative Alphaproteobacteria (within the order Rickettsiales) 108 associated with arthropods and filarial nematodes. Wolbachia cells resemble small 109 spheres 0.2-1.5 μ m, occur in all tissue types, but tend to be more prevalent in ovaries 110 and testicles of infected hosts, and are closely associated with the female germline 111 [...

Background Anastrepha fraterculus is recognized as a quarantine pest in several American countries. This fruit fly species is native to the American continent and distributed throughout tropical and subtropical regions. It has been reported as a complex of cryptic species, and at least eight morphotypes have been described. Only one entity of this complex, formerly named Anastrepha fraterculus sp. 1, is present in Argentina. Previous cytogenetic studies on this morphotype described the presence of sex chromosome variation identified by chromosomal size and staining patterns. In this work, we expanded the cytological study of this morphotype by analyzing laboratory strains and wild populations to provide information about the frequency and geographic distribution of these sex chromosome variants. We analyzed the mitotic metaphases of individuals from four laboratory strains and five wild populations from the main fruit-producing areas of Argentina, including the northwest (Tucumán and La Rioja), northeast (Entre Ríos and Misiones), and center (Buenos Aires) of the country. Results In wild samples, we observed a high frequency of X1X1 (0.94) and X1Y5 (0.93) karyomorphs, whereas X1X2 and X1Y6 were exclusively found at a low frequency in Buenos Aires (0.07 and 0.13, respectively), Entre Ríos (0.16 and 0.14, respectively) and Tucumán (0.03 and 0.04, respectively). X2X2 and X2Y5 karyomorphs were not found in wild populations but were detected at a low frequency in laboratory strains. In fact, karyomorph frequencies differed between wild populations and laboratory strains. No significant differences among A. fraterculus wild populations were evidenced in either karyotypic or chromosomal frequencies. However, a significant correlation was observed between Y5 chromosomal frequency and latitude. Conclusions We discuss the importance of cytogenetics to understand the possible route of invasion and dispersion of this pest in Argentina and the evolutionary forces acting under laboratory conditions, possibly driving changes in the chromosomal frequencies. Our findings provide deep and integral genetic knowledge of this species, which has become of relevance to the characterization and selection of valuable A. fraterculus sp. 1 strains for mass rearing production and SIT implementation.