Data from: Humidity stress and its consequences for male pre- and post-copulatory fitness traits in an insect

Global declines in insect abundance are of significant concern. While there is evidence that climate change is contributing to insect declines, we know little of the direct mechanisms responsible for these declines. Male fertility is compromised by increasing temperatures, and the thermal limit to fertility has been implicated as an important factor in the response of insects to climate change. However, climate change is affecting both temperature and hydric conditions, and the effects of water availability on male fertility have rarely been considered. Here we exposed male crickets Teleogryllus oceanicus to either low- or high-humidity environments while holding temperature constant. We measured water loss and the expression of both pre- and post-mating reproductive traits. Males exposed to a low-humidity environment lost more water than males exposed to a high-humidity environment. A male's cuticular hydrocarbon profile (CHC) did not affect the amount of water lost, and males did not adjust the composition of their CHC profiles in response to hydric conditions. Males exposed to a low-humidity environment were less likely to produce courtship song or produced songs of low quality. Their spermatophores failed to evacuate and their ejaculates contained sperm of reduced viability. The detrimental effects of low humidity on male reproductive traits will compromise male fertility and population persistence. We argue that limits to insect fertility based on temperature alone are likely to underestimate the true effects of climate change on insect persistence, and that the explicit incorporation of water regulation into our modelling will yield more accurate predictions of the effects of climate change on insect declines.全球昆虫种群数量下降已引发广泛关注。尽管有证据表明气候变化正在加剧昆虫衰退，但我们对引发此类衰退的直接机制仍知之甚少。气温升高会损害雄性昆虫的生育能力，而生育热极限被视为昆虫响应气候变化的关键影响因素之一。然而，气候变化同时会影响温度与湿度条件，而水分可利用性对雄性生育能力的影响却极少被研究关注。本研究将雄性澳洲钟蟋（Teleogryllus oceanicus）置于恒温的低湿度或高湿度环境中进行暴露处理，测定了其水分散失量，以及交配前与交配后两类繁殖相关性状的表达情况。结果显示，相较于高湿度环境中的雄性个体，低湿度环境下的雄性水分散失量显著更高。雄性个体的表皮碳氢化合物谱（cuticular hydrocarbon profile, CHC）并不会对其水分散失量产生影响，且雄性不会随湿度条件调整自身CHC的组成。处于低湿度环境的雄性，其产生求偶鸣声的概率更低，即便产生求偶鸣声，质量也相对较差；它们的精荚无法正常排出，且精液中的精子活力也出现了显著下降。低湿度对雄性繁殖性状的有害影响，会损害雄性生育能力并威胁种群存续。我们认为，仅基于温度的昆虫生育能力限制模型，很可能低估了气候变化对昆虫种群存续的真实影响；若能将水分调控机制明确纳入预测模型，将可更精准地预判气候变化对昆虫衰退的作用效果。