School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK.
Proc Biol Sci. 2012 Jul 22;279(1739):2868-76. doi: 10.1098/rspb.2012.0235. Epub 2012 Mar 21.
Plasticity in behaviour is of fundamental significance when environments are variable. Such plasticity is particularly important in the context of rapid changes in the socio-sexual environment. Males can exhibit adaptive plastic responses to variation in the overall level of reproductive competition. However, the extent of behavioural flexibility within individuals, and the degree to which rapidly changing plastic responses map onto fitness are unknown. We addressed this by determining the behaviour and fitness profiles of individual Drosophila melanogaster males subjected to up to three episodes of exposure to rivals or no rivals, in all combinations. Behaviour (mating duration) was remarkably sensitive to the level of competition and fully reversible, suggesting that substantial costs arise from the incorrect expression of even highly flexible behaviour. However, changes in mating duration matched fitness outcomes (offspring number) only in scenarios in which males experienced zero then high competition. Following the removal of competition, mating duration, but not offspring production, decreased to below control levels. This indicates that the benefit of increasing reproductive investment when encountering rivals may exceed that of decreasing investment when rivals disappear. Such asymmetric fitness benefits and mismatches with behavioural responses are expected to exert strong selection on the evolution of plasticity.
当环境发生变化时，行为的可塑性具有重要的意义。在社会性行为环境快速变化的背景下，这种可塑性尤为重要。雄性可以对生殖竞争整体水平的变化表现出适应性的可塑性反应。然而，个体内部的行为灵活性程度，以及快速变化的可塑性反应与适应性之间的关系尚不清楚。我们通过确定个体黑腹果蝇雄性在经历零个或多个竞争对手的情况下，其行为和适应性特征，来解决这个问题。行为（交配持续时间）对竞争水平的变化非常敏感，并且是完全可逆的，这表明即使是高度灵活的行为的错误表达也会带来巨大的代价。然而，只有在雄性经历了零竞争然后是高竞争的情况下，交配持续时间的变化才与适应性结果（后代数量）相匹配。在去除竞争后，交配持续时间，但不是后代的产生，会降低到低于对照水平。这表明，在遇到竞争对手时增加生殖投资的好处可能超过竞争对手消失时减少投资的好处。这种不对称的适应性收益和行为反应之间的不匹配，预计将对可塑性进化产生强烈的选择压力。
