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    Sex ratios in field populations of Epidinocarsis lopezi, an exotic parasitoid of the cassava mealybug, in Africa

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    Date
    1991
    Author
    Van Dijken, M.J.
    Neuenschwander, P.
    Van Alphen, J.J.M.
    Hammond, W.N.O.
    Type
    Journal Article
    Metadata
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    Abstract/Description
    1. In cassava fields in Africa, population sex ratios of Epidinocarsis fopezi vaned from 0.44 (males to total parasitoids) at low host densities to highly male-biased ratios of 0.70 at high host densities. 2. This variability is caused by the difference in allocation of sons and daughters to hosts of different sizes, through the following mechanisms: (a) small, i.e. second instar, hosts are mainly used for the production of male offspring, whereas in large, i.e. third instar, hosts a variable, female-biased sex ratio is produced; (b) E.fopezi does not selectively oviposit into large hosts but always accepts both small and large hosts for oviposition upon encountering; (c) in the field, this parasitoid is time-limited, and not egg-limited. On the basis of an optimal diet model, such general host acceptance is shown to be the best strategy. 3. Thus, sex ratio increases with host density for three reasons: the proportion of small hosts encountered in the field increases with increasing host density, small hosts are used for male production, and hosts are always accepted when encountered.
    Permanent link to this item
    https://hdl.handle.net/20.500.12478/5900
    IITA Subjects
    Cassava; Plant Production
    Agrovoc Terms
    Cassava; Fields; Production
    Regions
    Africa; West Africa
    Countries
    Nigeria
    Collections
    • Journal and Journal Articles4835
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