Data from: Male cognitive performance declines in the absence of sexual selection

Sexual selection is responsible for the evolution of male ornaments and armaments, but its role in the evolution of cognition—the ability to process, retain and use information—is largely unexplored. Because successful courtship is likely to involve processing information in complex, competitive sexual environments, we hypothesized that sexual selection contributes to the evolution and maintenance of cognitive abilities in males. To test this, we removed mate choice and mate competition from experimental populations of Drosophila melanogaster by enforcing monogamy for over 100 generations. Males evolved under monogamy became less proficient than polygamous control males at relatively complex cognitive tasks. When faced with one receptive and several unreceptive females, polygamous males quickly focused on receptive females, whereas monogamous males continued to direct substantial courtship effort towards unreceptive females. As a result, monogamous males were less successful in this complex setting, despite being as quick to mate as their polygamous counterparts with only one receptive female. This diminished ability to use past information was not limited to the courtship context: monogamous males (but not females) also showed reduced aversive olfactory learning ability. Our results provide direct experimental evidence that the intensity of sexual selection is an important factor in the evolution of male cognitive ability.

性选择（sexual selection）驱动了雄性装饰结构与武器的演化，但它在认知能力——即处理、储存与运用信息的能力——演化过程中所扮演的角色，迄今仍未得到充分探索。由于成功求偶往往需要在复杂且充满性竞争的环境中处理信息，我们提出假说：性选择有助于雄性认知能力的演化与维持。为验证这一假说，我们通过强制实行单配偶制超过100代，移除了黑腹果蝇（Drosophila melanogaster）实验种群中的配偶选择与配偶竞争环节。在相对复杂的认知任务中，经单配偶制演化的雄性，其表现不如实行多配偶制的对照组雄性。当面对1只可交配雌性与多只不可交配雌性时，多配偶制组雄性会迅速将注意力集中于可交配雌性，而单配偶制组雄性仍会向不可交配雌性投入大量求偶精力。尽管在仅存在1只可交配雌性的情境下，单配偶制组雄性的交配速度与多配偶制组雄性并无差异，但在上述复杂情境中，它们的交配成功率更低。这种利用过往信息的能力受损并非仅局限于求偶场景：仅在单配偶制组雄性（而非雌性）中，我们观察到厌恶性嗅觉学习能力出现下降。本研究结果提供了直接的实验证据，表明性选择强度是影响雄性认知能力演化的重要因素。