Comparative Genomic Hybridization (CGH) in Anastrepha fraterculus sp. 1 reveals active divergence between sex chromosomes

Abstract

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.