Kemp Darrell J
School of Tropical Biology, James Cook University, PO Box 6811, Cairns, Queensland 4870, Australia.
Proc Biol Sci. 2002 Jul 7;269(1498):1341-5. doi: 10.1098/rspb.2002.2000.
Trait evolution via sexual selection has traditionally been viewed as isolated from life-history constraints. Recent theoretical treatments, however, predict that costly sexually selected characters should be mediated by the same allocational trade-offs that apply to more conventional aspects of reproductive investment. Participation in risky competitive behaviours, for example male-male combat, should therefore increase as the opportunity for future reproduction declines. However, the demonstration of such trade-offs has proven to be elusive due to concomitant age-based variation in the physical determinants of fighting 'ability'. Here, I exploit the unique nature of a butterfly contest system to provide compelling evidence for lifetime partitioning of risky and aggressive sexually selected behaviours. I show that male Hypolimnas bolina become more willing to persist in contests over mating territories, and more generally accepting of injury risks, as they age. Contest persistence in this species is not mediated simply by physical condition, and I experimentally isolate the effect of ageing per se from resource ownership and previous contest experience. These results demonstrate how sexually selected behaviours can be ultimately mediated by a shifting trade-off between contemporary reproductive effort and future opportunities.
传统上，通过性选择的性状进化被认为与生活史限制无关。然而，最近的理论研究预测，代价高昂的性选择特征应该由与适用于生殖投资更传统方面相同的分配权衡来调节。例如，随着未来繁殖机会的减少，参与有风险的竞争行为，如雄性间的争斗，应该会增加。然而，由于与战斗“能力”的生理决定因素相关的基于年龄的伴随变化，这种权衡的证明一直难以捉摸。在这里，我利用蝴蝶竞争系统的独特性质，为有风险和攻击性的性选择行为的终生分配提供了令人信服的证据。我表明，雄性金斑蝶随着年龄的增长，更愿意在争夺交配领地的竞争中坚持下去，并且更普遍地接受受伤风险。该物种的竞争持久性不仅仅由身体状况调节，并且我通过实验将衰老本身的影响与资源所有权和以前的竞争经验隔离开来。这些结果表明，性选择行为最终如何通过当代生殖努力和未来机会之间不断变化的权衡来调节。
