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Female crickets avoid costs of inbreeding by mating with multiple males
  
By
Edward R. Winstead


 

The price of mating with a close relative in many species is genetic incompatibility, which can lead to disease. In crickets, the female can avoid the negative effects of inbreeding by mating with more than one male and, through an unknown mechanism, selecting the sperm of a genetically compatible father. This is the conclusion of a new study by British researchers.


Mating crickets.

Tom Tregenza and Nina Wedell, of the University of Leeds, U.K., analyzed the viability of eggs produced by different pairings of the field cricket Gryllus bimaculatus. They first mated female crickets separately with related and unrelated males; then they mated females sequentially with a brother and a non-sibling. Each mating exacted a cost for the female cricket, but the potential benefit in evolutionary terms was the increased viability of her eggs.

As expected, the eggs of females that mated with brothers were less viable than normal. But the eggs of females who mated with a sibling and a non-sibling were normal—as though the females had mated only with non-siblings. Their eggs showed none of the negative effects of inbreeding; in fact, these eggs were more viable than would be expected if related and unrelated males were equally successful in fertilizing the egg.

Tregenza and Wedell observed no behavior prior to the matings to indicate a female's recognition of male relatedness. They hypothesize that females may exercise choice by accepting less sperm from closely related males, or through mechanisms after the mating that reduce the chances that sperm from related males will fertilize eggs.

"We suggest that females may be able to avoid [the threat of inbreeding] to their reproductive success through some mechanism that enables them to preferentially fertilize their eggs with sperm from genetically compatible males," the researchers write in Nature. "If similar effects occur in other species, inbreeding avoidance may be important in understanding the prevalence of multiple mating."

See related GNN article
»Meaningless sex: Hens eject sperm; roosters are clueless

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Tregenza, T. & Wedell, N. Polyandrous females avoid costs of inbreeding. Nature 415, 71-73 (January 3, 2002).
 

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