Two species of true fruit flies (taxonomic family Tephritidae) are considered pests of fruit and vegetable production in Argentina: the cosmopolitan Mediterranean fruit fly (Ceratitis capitata Wiedemann) and the new world South American fruit fly (Anastrepha fraterculus Wiedemann). The distribution of these two species in Argentina overlaps north of the capital, Buenos Aires. Regarding the control of these two pests, the varied geographical fruit producing regions in Argentina are in different fly control situations. One part is under a programme using the sterile insect technique (SIT) for the eradication of C. capitata, because A. fraterculus is not present in this area. The application of the SIT to control C. capitata north of the present line with the possibility of A. fraterculus occupying the niche left vacant by C. capitata becomes a cause of much concern. Only initial steps have been taken to investigate the genetics and biology of A. fraterculus. Consequently, only fragmentary information has been recorded in the literature regarding the use of SIT to control this species. For these reasons, the research to develop a SIT protocol to control A. fraterculus is greatly needed. In recent years, research groups have been building a network in Argentina in order to address particular aspects of the development of the SIT for Anastrepha fraterculus. The problems being addressed by these groups include improvement of artificial diets, facilitation of insect mass rearing, radiation doses and conditions for insect sterilisation, basic knowledge supporting the development of males-only strains, reduction of male maturation time to facilitate releases, identification and isolation of chemical communication signals, and a good deal of population genetic studies. This paper is the product of a concerted effort to gather all this knowledge scattered in numerous and often hard-to-access reports and papers and summarize their basic conclusions in a single publication.

Cytogenetics, which is considered a fundamental tool to understand basic genetic and genomic issues of species, has greatly contributed to the description of polymorphisms both at inter- and intra-specific level. In fact, cytogenetics was one of the first approaches used to propose Anastrepha fraterculus (Diptera: Tephritidae) as a complex of cryptic species. Different morphological variants of sex chromosomes have been reported among Argentinean populations of A. fraterculus. However, since this high structural variability in sex chromosomes does not pose a reproductive barrier, their role in speciation is yet to be unveiled. This review provides an update on general aspects of cytogenetics in Argentinean A. fraterculus populations, focused on the prevalence of X-Y arrangements.

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. 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. 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.

Anastrepha fraterculus is an economically important fruit fly pest in South America, and it is currently recognized as a complex of cryptic species. This insect has a diploid chromosome number of 2n = 12, a XX/XY sex chromosome system and five pairs of autosomes. Specifically for the morphotype A. fraterculus sp. 1, the single member of this complex detected in Argentina, two variants of each sex chromosome have been described. In this study, we used comparative genomic hybridization (CGH) to assess the molecular differentiation of the most frequent sex chromosome variants registered so far and represented in a laboratory strain. Overall results showed that the X chromosome variants hybridized only with the female-derived probes. Conversely, the Y₅ chromosome exhibited a centromeric region positive for the female-derived probes while the rest of the chromosome hybridized exclusively with male DNA. These findings allow us to propose a divergent molecular differentiation between the studied sex chromosomes and provide a genetic background for characterizing the A. fraterculus sp. 1 morphotype. Moreover, our findings set the basis for the characterization of other members of the complex, thus promoting deeper studies on the evolutionary processes of differentiation and speciation occurring in A. fraterculus.

The authors of the manuscript titled “The Assembly of the Y Chromosome Reveals Amplification of Genes Regulating Male Fertility in _Bactrocera Dorsalis_” have made significant efforts to investigate the sequence of the Y chromosome in _Bactrocera dor...