A sex ratio theory of gregarious parasitoids

Yoshito Suzuki, Yoh Iwasa

Research output: Contribution to journalArticle

115 Citations (Scopus)

Abstract

A mathematical model is constructed to explain a density-dependent increase in the progeny sex ratios of gregarious parasitoids. In the model we considered non-cooperative game between females concerned with their own inclusive fitness. Equilibrium progeny sex ratios of the first and second females ovipositing on the same host are expressed in terms of the probability of double parasitism (p), the ratio of a male to a female in contribution to resource competition (α), the clutch size ratio between the two females (β), the crowding effect on female reproductive success (γ), and the inbreeding coefficient (f). Major predictions from the model are: 1) the progeny sex ratios of both the first and second females increase with p, 2) as β becomes smaller, the progeny sex ratios of the first females decrease, while those of the second females dramatically increases, 3) when a host is attacked by at most two wasps, the sex ratio of the total number of eggs laid on the host does not exceed 0.25. The effects of α and preferential death by female progeny in doubly parasitized hosts are considered as factors responsible for an excess number of males at emergence. Some possible modes of density-dependent increase in the sex ratios of the overall progeny populations is also discussed on the basis of the present model.

Original languageEnglish
Pages (from-to)366-382
Number of pages17
JournalResearches on Population Ecology
Volume22
Issue number2
DOIs
Publication statusPublished - Dec 1 1980

Fingerprint

Sex Ratio
sex ratio
parasitoids
Clutch Size
inclusive fitness
Wasps
Crowding
Inbreeding
inbreeding coefficient
clutch size
inbreeding
wasp
parasitism
Eggs
reproductive success
Theoretical Models
mathematical models
egg
death
prediction

All Science Journal Classification (ASJC) codes

  • Agricultural and Biological Sciences(all)

Cite this

A sex ratio theory of gregarious parasitoids. / Suzuki, Yoshito; Iwasa, Yoh.

In: Researches on Population Ecology, Vol. 22, No. 2, 01.12.1980, p. 366-382.

Research output: Contribution to journalArticle

Suzuki, Yoshito ; Iwasa, Yoh. / A sex ratio theory of gregarious parasitoids. In: Researches on Population Ecology. 1980 ; Vol. 22, No. 2. pp. 366-382.
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