Inexplicably female-biased sex ratios in Melittobia wasps

Jun Abe, Yoshitaka Kamimura, Stuart A. West

Research output: Contribution to journalArticlepeer-review

10 Citations (Scopus)


The sex ratio behavior of parasitoid wasps in the genus Melittobia is scandalous. In contrast to the prediction of Hamilton's local mate competition theory, and the behavior of numerous other species, their extremely female-biased sex ratios (1-5% males) change little in response to the number of females that lay eggs on a patch. We examined the mating structure and fitness consequences of adjusting the sex ratio in M. australica and found that (1) the rate of inbreeding did not differ from that expected with random mating within each patch; (2) the fitness of females that produced less female-biased sex ratios (10 or 20% males) was greater than that of females who produced the sex ratio normally observed in M. australica. These results suggest that neither assortative mating nor asymmetrical competition between males can explain the extreme sex ratios. More generally, the finding that the sex ratios produced by females led to a decrease in their fitness suggests that the existing theory fails to capture a key aspect of the natural history of Melittobia, and emphasizes the importance of examining the fitness consequences of different sex ratio strategies, not only whether observed sex ratios correlate with theoretical predictions.

Original languageEnglish
Pages (from-to)2709-2717
Number of pages9
Issue number9
Publication statusPublished - 2014


  • Adaptive behavior
  • Evolutionarily stable strategy
  • Game theory
  • Lethal male combat
  • Local mate competition
  • Sex allocation

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Genetics
  • Agricultural and Biological Sciences(all)


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