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Published on: January 4, 2017
Cytoplasmic incompatibility in Australian populations of Drosophila melanogaster
A A Hoffmann1, D J Clancy, E Merton
1Department of Genetics and Human Variation, La Trobe University, Bundoora, Victoria, Australia.
Abstract:
In Drosophila melanogaster, weak incompatibility in crosses between infected and uninfected strains is associated with a Wolbachia microorganism. Crosses between infected males and uninfected females show a reduction (15-30%) in egg hatch. Progeny tests indicated that the infection is widespread in Australian D. melanogaster populations and that populations are polymorphic for the presence of the infection. The infection status of 266 lines from 12 populations along the eastern coast of Australia was determined by 4',6-diamidino-2-phenylindole (DAPI) staining of embryos. All populations contained both infected and uninfected flies. Infection frequencies varied between populations but there was no discernible geographical pattern. Laboratory experiments indicated that the infection was not associated with a reduction in fecundity as in Drosophila simulans. Incompatibility levels could not be increased by laboratory selection on isofemale lines. Factors contributing to the persistence of the infection in D. melanogaster populations are discussed.
Insights
The common bacterium Wolbachia causes weak reproductive incompatibility in Australian fruit flies (Drosophila melanogaster). This widespread infection affects egg hatch rates but not fecundity, with varying infection levels across populations.
Area of Science:
- Microbiology
- Genetics
- Entomology
Background:
- Wolbachia is a bacterial endosymbiont known to cause reproductive incompatibilities in insects.
- Previous studies have documented Wolbachia's impact on Drosophila species, particularly Drosophila simulans.
- The prevalence and effects of Wolbachia in Australian Drosophila melanogaster populations were not well understood.
Purpose of the Study:
- To investigate the prevalence and impact of Wolbachia infections in Australian Drosophila melanogaster populations.
- To determine the effect of Wolbachia on reproductive compatibility, specifically egg hatch rates and fecundity.
- To explore factors influencing the persistence of Wolbachia in natural populations.
Main Methods:
- Surveyed 266 lines from 12 Australian populations for Wolbachia infection using DAPI staining of embryos.
- Conducted crosses between infected and uninfected flies to assess reproductive incompatibility (egg hatch rates).
- Performed laboratory selection experiments to test for changes in incompatibility levels.
Main Results:
- Wolbachia infections were widespread and polymorphic (both infected and uninfected flies present) in all surveyed Australian D. melanogaster populations.
- Infected males crossed with uninfected females showed a 15-30% reduction in egg hatch, indicating weak cytoplasmic incompatibility.
- The infection was not associated with reduced fecundity in D. melanogaster, unlike in D. simulans, and incompatibility levels did not increase with laboratory selection.
Conclusions:
- Wolbachia infections are common and persist in Australian Drosophila melanogaster populations, causing mild reproductive incompatibility.
- The absence of a geographical pattern in infection frequencies suggests complex population dynamics.
- Further research is needed to understand the specific factors contributing to Wolbachia's persistence in this host species.
