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Multiple paternity and postcopulatory sexual selection in a hermaphrodite: what influences sperm precedence in the garden snail Helix aspersa?

Authors

  • GUILLAUME EVANNO,

    Corresponding author
    1. Département d’Ecologie et Evolution, Bâtiment de Biologie, Université de Lausanne, CH-1015 Lausanne, Switzerland,
      Guillaume Evanno, Fax: + 41 21 692 42 65; E-mail: guillaume.evanno@unil.ch
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  • LUC MADEC,

    1. UMR CNRS 6553, Université de Rennes 1, Campus de Beaulieu, Avenue du Général, Leclerc, 35042 Rennes cedex, France,
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  • JEAN-FRANÇOIS ARNAUD

    1. UMR CNRS 8016, Laboratoire de Génétique et Evolution des Populations Végétales, Bât. SN2, Université de Lille 1, 59655 Villeneuve d’Ascq cedex, France
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Guillaume Evanno, Fax: + 41 21 692 42 65; E-mail: guillaume.evanno@unil.ch

Abstract

Sperm competition has been studied in many gonochoric animals but little is known about its occurrence in simultaneous hermaphrodites, especially in land snails. The reproductive behaviour of the land snail Helix aspersa involves several features, like multiple mating, long-term sperm storage and dart-shooting behaviour, which may promote sperm competition. Cryptic female choice may also occur through a spermatheca subdivided into tubules, which potentially allows compartmentalized sperm storage of successive mates. In order to determine the outcome of postcopulatory sexual selection in this species, we designed a cross-breeding experiment where a recipient (‘female’) mated with two sperm donors (‘males’). Mates came from either the same population as the recipient or from a distinct one. To test for the influence a recipient can have on the paternity of its offspring, we excluded the effects of dart shooting by using only virgin snails as sperm donors because they do not shoot any dart before their first copulation. We measured the effects of size of mates as well as time to first and second mating on second mate sperm precedence (P2; established using microsatellite markers). Multiple paternity was detected in 62.5% of clutches and overall there was first-mate sperm precedence with a mean P2 of 0.24. Generalized linear modelling revealed that the best predictors of paternity were the time between matings and the time before first mating. Overall, both first and second mates that copulated quickly got greater parentage, which may suggest that postcopulatory events influence patterns of sperm precedence in the garden snail.

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