Sexual selection in sticklebacks in the field: correlates of reproductive, mating, and paternal success |
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Authors: | Kraak Sarah B M; Bakker Theo C M; Mundwiler Beat |
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Institution: | Abt. Verhaltensökologie,
Zoologisches Institut, University of Bern, Wohlenstrasse 50a, CH-3032
Hinterkappelen, Switzerland |
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Abstract: | Male sticklebacks display multiple ornaments, and these ornamentshave been
shown to be preferred by females in laboratory experiments.However, few field
data exist, and it is not known whether thesepreferences are simultaneously
or sequentially operative ina single population. We report correlates of
reproductive successin two stickleback populations that differ in their
ecology,over several periods within their breeding season. In both
populationslarger males had higher reproductive success, but not in all
periodsof the breeding season. Reproductive success increased withredness of
the throat only in the Wohlensee population, andonly in one period that was
characterized by low average success.In the Wohlensee population, the
parasitic worm Pomphorhynchuslaevis is abundant, and reproductive
success decreased withthe presence of the parasite. In the Roche population,
maleswith nests concealed in a plant had higher mating success. Thesenests
were less likely to fail, suggesting that females preferredto spawn in
concealed nests because of higher offspring survivorship.The different sexual
traits appear to reveal different aspectsof male quality (multiple message
hypothesis): females probablyfind large males attractive because of their
higher paternalquality, but it seems more likely that red males are preferred
forbetter genetic qualities. Females also discriminate on territoryquality,
and male traits may be important in competition forthese territories. The
correlates of reproductive success werenot consistent during the season,
probably due to changes inthe availability of ripe females. Such fluctuating
selectionpressures will contribute to the maintenance of genetic variationin
sexual traits. |
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Keywords: | embryo survivorship Gasterosteus aculeatus mating success multiple ornaments nest concealment optimum brood size paternal effort paternal success Pomphorhynchus laevis reproductive success sexual selection sticklebacks |
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