Sex Ratios in a Socially Parasitic Bee and Implications for Host-Parasite Interactions

Nahid Shokri Bousjein, Morgan Staines, Cathy Vo, Natalie Puiu, Carmen da Silva, Jack Harrington, Sara Wilkinson, Kelly Pratt, Michael Schwarz

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    2 Citations (Scopus)


    Obligate social parasites of Hymenoptera, known as inquilines, have received enormous attention due to the elaborate adaptations they exhibit for exploiting their hosts, and because they have frequently been used to infer sympatric speciation. Their population biology can be difficult to infer as they are both rare and difficult to extract from host nests. Sex allocation has been studied for very few inquilines of social Hymenoptera. Here we report sex ratio patterns in the allodapine bee Inquilina schwarzi, which is an obligate social parasite of another allodapine, Exoneura robusta. We show that the sex ratio of this inquiline varies with its brood number, it is female-biased in the smallest broods, but becomes more even in larger broods, where the population-wide sex ratio is close to parity. We argue that this pattern of bias is consistent with local resource competition, where inquiline females compete to inherit their natal colony. We also argue that extremely female-biased sex ratios of the host species, combined with overall sex ratio parity in the parasite, may help ameliorate disparity in effective population sizes between these two species which are locked in an evolutionary arms race.

    Original languageEnglish
    Pages (from-to)130-137
    Number of pages8
    JournalJournal of Insect Behavior
    Issue number1
    Publication statusPublished - Jan 2017


    • Bees
    • effective population size
    • inquilines
    • local resource competition
    • sex ratio
    • social parasites


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