Dynamic resource allocation between pre- and postcopulatory episodes of sexual selection determines competitive fertilization success.
In polyandrous mating systems, male reproductive success depends on both mate-acquisition traits (precopulatory) and sperm competitive abilities (postcopulatory). Empirical data on the interaction between these traits are inconsistent; revealing positive, negative or no relationships. It is generally expected that the investment in pre- and postcopulatory traits is mediated by environmental conditions. To test how dietary resource availability affects sexual ornamentation, sperm quality and their interrelationship in three-spined sticklebacks (Gasterosteus aculeatus), full-sibling groups were raised under three conditions differing in food quantity and/or quality (i.e. carotenoid content): (i) high-quantity/high-quality, (ii) high-quantity/low-quality or (iii) low-quantity/low-quality. After 1 year of feeding, food-restricted males developed a more intense breeding coloration and faster sperm compared with their well-fed brothers, indicating that they allocated relatively more in pre- and postcopulatory traits. Moreover, they outcompeted their well-fed, carotenoid-supplemented brothers in sperm competition trials with equal numbers of competing sperm, suggesting that food-restricted males maximize their present reproductive success. This may result in reduced future reproductive opportunities as food-restricted males suffered from a higher mortality, had an overall reduced body size, and sperm number available for fertilization. In accordance with theory, a trade-off between the investment in pre- and postcopulatory traits was observed in food-restricted males, whereas well-fed males were able to allocate to both traits resulting in a significantly positive relationship.
Institute for Evolutionary Biology and Ecology, University of Bonn, An der Immenburg 1, Bonn 53121, Germany mmehlis@evolution.uni-bonn.de.
Marion
M
Mehlis
Institute for Evolutionary Biology and Ecology, University of Bonn, An der Immenburg 1, Bonn 53121, Germany.
Ingolf P
IP
Rick
Institute for Evolutionary Biology and Ecology, University of Bonn, An der Immenburg 1, Bonn 53121, Germany.
Theo C M
TC
Bakker
D000818:Animals; D049628:Body Size; D002338:Carotenoids; D004032:Diet; D005260:Female; D005306:Fertilization / Q000502:physiology*; D005508:Food Deprivation / Q000502:physiology; D008297:Male; D018895:Microsatellite Repeats; D040841:Resource Allocation; D023701:Smegmamorpha / Q000502:physiology*; D013094:Spermatozoa / Q000502:physiology*
D002338:Carotenoids
carotenoids; mate choice; resource availability; sperm competition; stickleback; trade-off