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Sexual conflict selects for male and female reproductive characters.


Hosken, D J; Garner, T W J; Ward, Paul I (2001). Sexual conflict selects for male and female reproductive characters. Current Biology, 11(7):489-493.

Abstract

BACKGROUND: Strict genetic monogamy leads to sexual harmony because any trait that decreases the fitness of one sex also decreases the fitness of the other. Any deviation from monogamy increases the potential for sexual conflict. Conflict is further enhanced by sperm competition, and given the ubiquity of this phenomenon, sexual conflict is rife. In support of theory, experimentally enforced monogamy leads to the evolution of sexual benevolence. In contrast, with multiple mating, males evolve traits causing massive female fitness reductions when female evolution is restrained. Theory also predicts increased investment in spermatogenesis when sperm competition risk is high. While this supposition has correlational support, cause and effect has yet to be firmly established. RESULTS: By enforcing monogamy or polyandry in yellow-dung-fly lines, we have shown experimentally that males from polyandrous treatments evolved larger testes. Furthermore, females from this treatment evolved larger accessory sex glands. These glands produce a spermicidal secretion, so larger glands could increase female ability to influence paternity. Using molecular techniques, we have shown that, consistent with this idea, males' success as second mates is reduced in females from the polyandrous treatment. Nevertheless, males from polyandrous lines achieve higher paternity during sperm competition, and this finding further supports the testis evolution patterns. CONCLUSIONS: These results provide direct experimental support for macroevolutionary patterns of testis size evolution. Furthermore, we have shown that sperm competition selects for traits likely to be important in sexual conflicts over paternity, a result only previously demonstrated in Drosophila melanogaster.

BACKGROUND: Strict genetic monogamy leads to sexual harmony because any trait that decreases the fitness of one sex also decreases the fitness of the other. Any deviation from monogamy increases the potential for sexual conflict. Conflict is further enhanced by sperm competition, and given the ubiquity of this phenomenon, sexual conflict is rife. In support of theory, experimentally enforced monogamy leads to the evolution of sexual benevolence. In contrast, with multiple mating, males evolve traits causing massive female fitness reductions when female evolution is restrained. Theory also predicts increased investment in spermatogenesis when sperm competition risk is high. While this supposition has correlational support, cause and effect has yet to be firmly established. RESULTS: By enforcing monogamy or polyandry in yellow-dung-fly lines, we have shown experimentally that males from polyandrous treatments evolved larger testes. Furthermore, females from this treatment evolved larger accessory sex glands. These glands produce a spermicidal secretion, so larger glands could increase female ability to influence paternity. Using molecular techniques, we have shown that, consistent with this idea, males' success as second mates is reduced in females from the polyandrous treatment. Nevertheless, males from polyandrous lines achieve higher paternity during sperm competition, and this finding further supports the testis evolution patterns. CONCLUSIONS: These results provide direct experimental support for macroevolutionary patterns of testis size evolution. Furthermore, we have shown that sperm competition selects for traits likely to be important in sexual conflicts over paternity, a result only previously demonstrated in Drosophila melanogaster.

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Additional indexing

Item Type:Journal Article, refereed
Communities & Collections:07 Faculty of Science > Institute of Zoology (former)
Dewey Decimal Classification:570 Life sciences; biology
590 Animals (Zoology)
Language:English
Date:3 April 2001
Deposited On:11 Feb 2008 12:15
Last Modified:05 Apr 2016 12:14
Publisher:Elsevier
ISSN:0960-9822
Publisher DOI:10.1016/S0960-9822(01)00146-4
PubMed ID:11412998
Permanent URL: http://doi.org/10.5167/uzh-537

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