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Updated: Jul 15, 2026
09:34
Assessing Differences in Sperm Competitive Ability in Drosophila
Published on: August 22, 2013
Shorter sperm confer higher competitive fertilization success
Francisco García-González1, Leigh W Simmons
1Centre for Evolutionary Biology, School of Animal Biology (M092), The University of Western Australia, Nedlands, Western Australia 6009, Australia. pgarcia@cyllene.uwa.edu.au
Evolution; International Journal of Organic Evolution
|April 19, 2007
Summary
In dung beetles, shorter sperm increase fertilization success during sperm competition. Female reproductive tract morphology influences this selection, supporting theories of "sexy sperm" and "good sperm" evolution.
Area of Science:
- Evolutionary biology
- Reproductive biology
- Animal behavior
Background:
- Sperm morphology varies widely across species, but its adaptive significance is poorly understood.
- Sperm competition is a major evolutionary force shaping male reproductive traits.
Purpose of the Study:
- To investigate the role of natural variation in sperm length on fertilization success in the dung beetle Onthophagus taurus.
- To determine if female reproductive tract morphology influences sperm length selection during sperm competition.
Main Methods:
- Conducted sperm competition trials between males with differing sperm lengths.
- Used amplified fragment length polymorphism (AFLP) markers to determine offspring paternity.
- Quantified variation in female sperm storage organ (spermatheca) size and shape.
Main Results:
- Fertilization success was biased toward males with shorter sperm.
- Selection on sperm length was dependent on female spermathecal morphology.
- Directional selection for reduced sperm length occurred in most females, but stabilizing selection was observed in females with the smallest spermathecae.
Conclusions:
- Provides empirical support for the theory that sperm competition favors numerous, small sperm.
- Sperm length heritability and genetic correlation with condition suggest females may gain genetic benefits through sperm competition or cryptic female choice.
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