RESUMEN
Zaprionus indianus is a dipteran (Drosophilidae) with a wide distribution throughout the tropics and temperate Palearctic and Nearctic regions. There have been proposals to reclassify the genus Zaprionus as a subgenus or group of the genus Drosophila because various molecular markers have indicated a close relationship between Zaprionus species and the immigrans-Hirtodrosophila radiation within Drosophila. These markers, together with alloenzymes and quantitative traits, have been used to describe the probable scenario for the expansion of Zaprionus indianus from its center of dispersal (Africa) to regions of Asia (ancient dispersal) and the Americas (recent dispersal). The introduction of Z. indianus into Brazil was first reported in 1999 and the current consensus is that the introduced flies came from high-latitude African populations through the importation of fruit. Once in Brazil, Z. indianus spread rapidly throughout the Southeast and then to the rest of the country, in association with highway-based fruit commerce. These and other aspects of the evolutionary biology of Z. indianus are addressed in this review, including a description of a probable route for this species' dispersal during its recent expansion.
RESUMEN
The fruit flies Drosophila mulleri and Drosophila navojoa are included in the mulleri complex of the mulleri subgroup and Repleta group. Although there is no demonstration that interspecific crosses between them occur in nature, they intercross in the laboratory in both cross directions. Previous data have shown the occurrence of nucleolar dominance in interspecific hybrids of some species in the mulleri complex. We investigated nucleolar dominance in D. mulleri/D. navojoa hybrids using the transcription profiles of the rDNA internal transcribed spacer (ITS-1) region. The results showed that the ribosomal cistrons present in the X chromosome and in the microchromosome of D. navojoa are exclusively or preferentially transcribed in these hybrids depending on the cross direction, denoting the complete or partial nucleolar dominance of this species over D. mulleri.
