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Dynamics of cytoplasmic incompatibility and mtDNA variation in natural Drosophila simulans populations

M Turelli1, A A Hoffmann, S W McKechnie

  • 1Department of Genetics, University of California, Davis 95616.

Genetics
|November 1, 1992
PubMed

Insights

A microorganism in Drosophila simulans reduces egg hatch and spreads northward. Infected flies share one mitochondrial DNA (mtDNA) type, while uninfected flies show variation, suggesting imperfect maternal transmission is key.

Area of Science:

  • Evolutionary Biology
  • Genetics
  • Microbiology

Background:

  • A cytoplasmically transmitted microorganism in Drosophila simulans reduces egg hatch rates when infected males mate with uninfected females.
  • This infection is exhibiting rapid northward expansion within California populations.

Purpose of the Study:

  • To investigate the association between the spread of this microorganism and mitochondrial DNA (mtDNA) variant frequencies.
  • To understand the transmission dynamics of the microorganism in natural populations.

Main Methods:

  • Analysis of a specific mtDNA restriction site length polymorphism in infected and uninfected Drosophila simulans.
  • Comparison of mtDNA variant frequencies in relation to infection status and geographical spread.
  • Development and application of a population dynamics model.

Main Results:

  • All infected flies exclusively possess a single mtDNA allele, whereas uninfected flies display polymorphism.
  • Observed mtDNA variant frequencies align with a model where imperfect maternal transmission and/or loss of infection during transmission is more prevalent than paternal transmission.
  • The model successfully describes the joint frequencies of mtDNA variants and cytoplasmic incompatibility types.

Conclusions:

  • The spread of the microorganism is strongly correlated with specific mtDNA variants in Drosophila simulans.
  • Data suggest that maternal transmission of the microorganism is imperfect, with significant loss occurring during transmission, which influences population genetics.
  • Population dynamics modeling supports the observed patterns, highlighting the importance of transmission efficiency in the spread of infectious agents.

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