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.

昆虫种群丰度的全球性下降已引发学界广泛关注。尽管已有证据表明气候变化是昆虫种群下降的诱因之一，但我们对引发该现象的直接机制仍知之甚少。温度升高会损害雄性生育力，而生育热极限被认为是昆虫应对气候变化的重要影响因素。然而，气候变化同时影响温度与水分条件，现有研究却极少考虑水分可获得性对雄性生育力的作用。本研究将雄性大洋蟋（Teleogryllus oceanicus）置于恒定温度下的低湿度或高湿度环境中，测定了其水分散失量以及交配前、交配后生殖性状的表达情况。结果显示，低湿度环境中的雄性个体水分散失量显著高于高湿度环境中的个体。雄性的表皮碳氢化合物谱（cuticular hydrocarbon profile, CHC）并不会影响其水分散失量，且雄性个体也不会根据水分条件调整其表皮碳氢化合物谱的组成。处于低湿度环境的雄性个体更不易产生求偶鸣曲，或仅能生成质量较差的鸣曲；其精荚无法正常排出，且精液中的精子活力显著降低。低湿度对雄性生殖性状的不利影响会损害雄性生育力，并威胁种群存续。我们认为，仅基于温度的昆虫生育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，若在建模过程中明确纳入水分调控因素，将能更精准地预测气候变化对昆虫种群下降的作用效应。