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Measuring polyandry in wild populations: a case study using promiscuous crickets

Authors

  • AMANDA BRETMAN,

    Corresponding author
    1. Ecology and Evolution Group, School of Biology, University of Leeds, Leeds, LS2 9JT, UK
    2. Centre for Ecology and Conservation, University of Exeter in Cornwall, Tremough, Penryn, TR10 9EZ, UK
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  • TOM TREGENZA

    1. Ecology and Evolution Group, School of Biology, University of Leeds, Leeds, LS2 9JT, UK
    2. Centre for Ecology and Conservation, University of Exeter in Cornwall, Tremough, Penryn, TR10 9EZ, UK
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Amanda Bretman, Fax: 01326 253638; E-mail: A.J.Bretman@exeter.ac.uk

Abstract

Mating rate has important implications for patterns of sexual selection and sexual conflict and hence for issues such as speciation and the maintenance of genetic diversity. Knowledge of natural mating rates can provide insights into the factors driving female mating behaviour. We investigated the level of polyandry in a Spanish population of the field cricket Gryllus bimaculatus using microsatellite markers. Two approaches were employed: (i) genotyping the offspring of wild-caught gravid females to determine the number of males siring the brood and (ii) genotyping sperm stored in the spermathecae of females mated in the wild to estimate the number of mating partners. We compared existing methods for inferring the minimum and probable number of fathers and described a novel probabilistic technique estimating the number of mates by genotyping stored sperm. Using the most conservative allele-counting method, 71% of females produced offspring sired by at least two males (a minimum mean of 2.4 fathers per clutch), and all females had mated to at least two males with minimum mean estimates of 2.7–5.1 mates per female. Our study reveals high levels of polyandry in the wild and suggests that females mate with more males than sire their offspring.

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