Coexistence of a sexual and an unisexual form stabilized by parasites

Hiroshi Hakoyama, Yoh Iwasa

Research output: Contribution to journalArticlepeer-review

11 Citations (Scopus)


An unisexual species (either parthenogenetic or gynogenetic form) often coexists sympatrically with a closely related anisogamous sexual species, forming a unisexual complex. This is puzzling because, all else being equal, a sexual population with the two-fold cost of sex (or the cost of producing males) cannot coexist with a unisexual population. This suggests that some ecological processes are at work to make possible the coexistence of the unisexual complex. Field and laboratory studies suggest that parasitism in a gynogenetic complex of the Japanese crucian carp (Carassius auratus) may play an important role in realizing the coexistence by giving frequency-dependent benefit to sexual population. Here, we study the simple dynamics of host-parasite interactions in which non-specific immune reaction of a sexual host is more effective than that of an unisexual host. We simply assume that the infective individuals are sterile. Stable coexistence of a unisexual species with their sexual relative is possible if pathogens are virulent and if the susceptibility of the unisexual form is more than twice as high as that of the sexual form. The coexistence is more difficult, when the fertility of males is relatively low in gynogenetic complexes. This implies that the coexistence of gynogenetic complexes is more difficult than that of parthenogenetic complexes in which parthenogenesis has no constraint on males. We conclude that parasitism is a promising candidate mechanism for the coexistence of unisexual complexes.

Original languageEnglish
Pages (from-to)185-194
Number of pages10
JournalJournal of Theoretical Biology
Issue number2
Publication statusPublished - Jan 21 2004

All Science Journal Classification (ASJC) codes

  • Statistics and Probability
  • Modelling and Simulation
  • General Biochemistry,Genetics and Molecular Biology
  • General Immunology and Microbiology
  • General Agricultural and Biological Sciences
  • Applied Mathematics


Dive into the research topics of 'Coexistence of a sexual and an unisexual form stabilized by parasites'. Together they form a unique fingerprint.

Cite this