Sperm transfer and paternity in the scorpionfly <Emphasis Type="Italic">Panorpa cognata</Emphasis>: large variance in traits favoured by post-copulatory episodes of sexual selection |
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Authors: | Leif Engqvist Gabriele Dekomien Tanja Lippmann Jörg T Epplen Klaus P Sauer |
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Institution: | (1) Department of Evolutionary Biology and Ecology, University of Bonn, An der Immenburg 1, 53121 Bonn, Germany;(2) Human Genetics, Ruhr-University, Bochum, Germany |
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Abstract: | Post-copulatory episodes of sexual selection can be a powerful selective force influencing the reproductive success of males.
In order to understand variation in male fertilisation success, we first need to consider the pattern of sperm utilisation
by females following matings with more than one male. Second, we need to study those traits responsible for male success in
sperm competition. Here we study both male sperm transfer characteristics as well as offspring paternity of females mated
to two males in the scorpionfly Panorpa cognata. By repeatedly mating males to virgin females and interrupting copulation at defined time points, we found for all males
that sperm transfer set off after approximately 40 min. During the remaining copulation, sperm transfer of individual males
was continuous and with constant rate. Yet the rate of sperm transfer differed between individual males from about one sperm
per minute to more than eight sperm per minute for the most successful males. In addition, we measured the fertilisation success
in sperm competition of males with known sperm transfer capability. The relative number of sperm transferred by males during
copulation, estimated from copulation duration and the males’ individual sperm transfer rate, explained a large proportion
of variation in offspring paternity. The mode of sperm competition in this species, thus, conforms largely to a fair raffle
following complete mixing of sperm prior to fertilisation. Hence, male differences in both the ability to copulate for long
and of rapid sperm transfer will translate directly into differences in reproductive success. |
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Keywords: | Copulation duration Cryptic female choice Fair raffle Mecoptera Microsatellites Sperm competition Sperm precedence |
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