Impacts of diet quality on life-history and reproductive traits in male and female armed beetle, Gnatocerus cornutus

1. The energy available for reproduction is usually limited by resource acquisition (i.e. condition). Because condition is known to be strongly affected by environmental factors, reproductive investments also vary across heterogeneous environments. 2. Although the condition dependence of reproductive investment is common to both sexes, reproductive traits may exhibit sexually different responses to environmental fluctuation due to sex-specific life-history strategies. However, few direct experimental studies have investigated the condition dependence of reproductive investments in both sexes. 3. We investigated the condition dependence of life-history and reproductive traits of males and females in the beetle Gnatocerus cornutus Fabricus by manipulating larval and adult diet quality. We found that male and female life-history traits exhibited similar responses to environmental fluctuations. 4. By contrast, the sexes exhibit different patterns of condition dependence in reproductive traits (i.e. the adult nutritional environment has a strong impact on the female lifetime reproductive success, whereas larval nutritional environment strongly affects the secondary sexual trait in males). 5. This difference in the plasticity of reproductive traits may lead to different selection pressures for each sex, even if both sexes develop and/or live in the same environment.

1. 可用于繁殖的能量通常受到资源获取（即身体状况）的限制。因为已知身体状况受环境因素的强烈影响，所以在不同的环境中繁殖投入也会有所不同。 2. 尽管繁殖投入对身体状况的依赖性在两性中都很常见，但由于性别特异性的生活史策略，繁殖特征可能对环境波动表现出性别差异的反应。然而，很少有直接的实验研究对两性繁殖投入的身体状况依赖性进行调查。 3. 我们通过控制幼虫和成虫的饮食质量，研究了阔角谷盗（Gnatocerus cornutus Fabricus）雄性和雌性的生活史及繁殖特征对身体状况的依赖性。我们发现雄性和雌性的生活史特征对环境波动表现出相似的反应。 4. 相比之下，两性在繁殖特征上表现出不同的身体状况依赖性模式（即成年期的营养环境对雌性的终生繁殖成功率有强烈影响，而幼虫期的营养环境则强烈影响雄性的第二性征）。 5. 繁殖特征可塑性的这种差异可能导致两性面临不同的选择压力，即使两性在相同的环境中发育和/或生活。