Male genital traits and mating interval affect male fertilization success in the water strider Gerris lacustris |
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Authors: | Ingela Danielsson Conny Askenmo |
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Institution: | Animal Ecology, Department of Zoology G?teborg University, Box 463 SE-40530 G?teborg, Sweden e-mail: ingela.danielsson@zool.gu.se Tel.: +46-31-7733656, Fax: +46-31-416729, SE
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Abstract: | Parker's seminal work brought attention to the possibility of postmating sexual selection by non-random fertilization success.
Mechanisms for these processes are still only partly understood and there is clearly a need for more studies of intraspecific
variation in sperm precedence. Here, we report results from an experimental study of the variation in fertilization success
between males of the water strider Gerris lacustris. Genital morphology, male body size, and copulation duration were examined as possible correlates of paternity. The significance
of guarding duration was also analysed. Only male genital morphology was correlated to fertilization success. This is one
of the first studies showing a relationship between male genital traits and fertilization success, supporting the view that
sexual selection may be responsible for the rapid and divergent evolution of genital structures in animals with internal fertilization.
The fertilization success of last males varied considerably after double matings with a short mating interval (10 min). Last-male
priority ranged from 0 to 100% and usually one of the males involved fertilized almost all the eggs. After double matings
with a short mating interval, the proportion of eggs fertilized by the last male averaged 0.68 and was greater than 0.5. In
contrast, the average fertilization success was biased towards the first male when the matings were more spread out over time
(24 h). These results do not support earlier suggestions of a widespread last-male sperm priority in water striders.
Received: 28 July 1998 / Received in revised form: 15 March 1999 / Accepted: 28 March 1999 |
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Keywords: | Sperm competition Sperm precedence Male genital morphology Mating interval Sexual selection Sterile-male technique |
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