Infectious Hybrid Sterility and the “New Llanos” Strain of Drosophila paulistorum

Abstract

Drosophila paulistorum Dobzhansky and Pavan is a complex of five semispecies1 from South and Central America (Centro-American, Amazonian, Andean–South Brazilian, Orinocan, Transitional). A closely related species is D. pavlovskiana Kastritsis and Dobzhansky2. With the exception of some strains of the Transitional semispecies, crosses between these semispecies result in the production of fertile hybrid females but sterile hybrid males. The Transitional semispecies produces fertile hybrids with at least one strain of some other semispecies. The Santa Marta and Mesitas strains, both originating in Colombia, South America, and belonging to the Transitional semispecies, display a cytoplasmically inherited male sterility when Santa Marta serves as the female parent. Thus matings between Santa Marta females and Mesitas males yielded fertile female but sterile male progenies; while the reciprocal cross, Mesitas ♀ × Santa Marta ♂, gave fertile progeny of both sexes3. Recently, however, sterile F1 hybrid sons have been obtained also from the latter cross4. The F1 male hybrid sterility of the Santa Marta ♀ × Mesitas ♂ cross has been found to be artificially transferable to Mesitas females by injection of homogenates from sterile F1 males5,6. Such an induced sterility persists only in the male progeny of the injected mothers, and is apparently not transmitted through daughters of the injected females to their sons.