Department of Zoology, Stockholm University, Stockholm, Sweden.
J Anim Ecol. 2022 Feb;91(2):391-403. doi: 10.1111/1365-2656.13636. Epub 2021 Nov 24.
Temperature and thermal variability are increasing worldwide, with well-known survival consequences. However, effects on other potentially more thermally sensitive reproductive traits are less understood, especially when considering thermal variation. Studying the consequences of male reproduction in the context of climate warming and ability to adapt is becoming increasingly relevant. Our goals were to test how exposure to different average temperatures that either fluctuated or remained constant impacts different male reproductive performance traits and to assess adaptive potential to future heat stress. We took advantage of a set of Drosophila melanogaster isogenic lines of different genotypes, exposing them to four different thermal conditions. These conditions represented a benign and a stressful mean temperature, applied either constantly or fluctuating around the mean and experienced during development when heat stress avoidance is hindered because of restricted mobility. We measured subsequent male reproductive performance for mating success, fertility, number of offspring produced and offspring sex ratio, and calculated the influence of thermal stress on estimated heritability and evolvability of these reproductive traits. Both costs and benefits to different thermal conditions on reproductive performance were found, with some responses varying between genotypes. Mating success improved under fluctuating benign temperature conditions and declined as temperature stress increased regardless of genotype. Fertility and productivity were severely reduced at fluctuating mean high temperature for all genotypes, but some genotypes were unaffected at constant high mean temperature. These more thermally robust genotypes showed a slight increase in productivity under the fluctuating benign condition compared to constant high temperature, despite both thermal conditions sharing the same temperature for 6 hr daily. Increasing thermal stress resulted in higher heritability and evolvability. Overall, the effects of temperature on reproductive performance depended on the trait and genotype; performance of some traits slightly increased when high temperatures were experienced for short periods but decreased substantially even when experiencing a benign temperature for a portion of each day. While thermal stress increased genetic variation that could provide adaptive potential against climate warming, this is unlikely to compensate for the overall severe negative effect on reproductive performance as mean temperature and variance increase.
全球范围内，温度和热变异性不断增加，这对生物生存产生了众所周知的影响。然而，对于其他可能对热更敏感的生殖特征的影响，人们的了解较少，尤其是在考虑到热变异性的情况下。研究雄性生殖在气候变暖背景下的后果及其适应能力变得越来越重要。我们的目标是测试暴露于不同平均温度（恒温或变温）对不同雄性生殖性能特征的影响，并评估对未来热应激的适应潜力。我们利用一组不同基因型的黑腹果蝇近等基因系，将它们暴露于四种不同的热条件下。这些条件代表了一个良性和一个应激的平均温度，无论是恒温还是在变温条件下，以及在发育过程中都有体现，因为受限的移动性会阻碍对热应激的逃避。我们测量了随后的雄性生殖性能，包括交配成功率、生育能力、后代数量和后代性别比，并计算了热应激对这些生殖特征的遗传力和可进化性的影响。发现不同热条件对生殖性能既有成本又有收益，一些反应在不同基因型之间存在差异。在恒温条件下，交配成功率在波动的良性温度条件下提高，而无论基因型如何，随着温度应激的增加而下降。在所有基因型中，波动的高平均温度下的生育能力和生产力严重降低，但在恒温高平均温度下，一些基因型不受影响。与恒温高温度相比，这些更耐热的基因型在波动的良性条件下生产力略有提高，尽管这两种热条件每天有 6 小时共享相同的温度。随着热应激的增加，遗传力和可进化性增加。总体而言，温度对生殖性能的影响取决于性状和基因型；在短时间内经历高温时，某些性状的表现略有提高，但即使在每天的一部分时间内经历良性温度时，也会大幅下降。虽然热应激增加了可以提供适应气候变化潜力的遗传变异，但由于平均温度和方差的增加，这不太可能补偿对生殖性能的整体严重负面影响。
