Will fertility loss at high temperatures determine species responses to climate change?

气候正在变暖，预计这将导致极端气温的增加。如果我们要防止物种的大规模损失和有害害虫的入侵，了解这将如何影响生物的生存和分布是至关重要的。气候变化的影响通常是通过检查导致动物死亡的温度来估计的。然而，这可能有缺陷。在大多数动物中，从甲虫到鸟类再到獾，雄性通常会在远低于杀死它们所需温度的温度下失去生育能力。如果温度升高导致一个种群中的所有雄性不育，那么这个种群将无法生存，即使温度远没有高到足以杀死任何动物的程度。不幸的是，对此很少有系统的调查，所以我们不知道温度升高对男性生育能力的可能影响是否真的可能对大自然构成威胁。我们将通过研究生态相关的高温对雄性果蝇生育力的影响来纠正这种情况。我们首先关注一个模式物种，d.p pseudobscura，以提供温度如何影响生育力的详细检查。我们将确定高温和极端温度冲击对男性生育能力的影响，以及较低的夜间温度是否可以恢复生育能力。在许多昆虫和爬行动物中，在与雄性交配后，雌性可能会将精子储存数周、数月甚至数年。在某些情况下，雌性比雄性更善于在极端温度下保存精子，因为在恶劣的环境中，许多物种的雄性昆虫往往比雌性死得更快。我们将研究女性精子储存是否可以改善温度对男性生育能力的影响。最重要的是，这项研究将使我们能够制定标准技术来评估温度对男性生育能力的影响。有了从这个案例研究中获得的知识，我们将研究温度对50个果蝇物种的生育能力的影响，这些物种经过精心挑选，涵盖了一系列的生活方式、栖息地和温度，包括热带物种、温带物种和遍布全球的物种。最重要的是，所有这些物种都是众所周知的，有关于它们所生活的气候的优秀数据，以及它们在实验室中生存的温度。我们将计算出所有50个物种的生育影响，然后能够将其与物种的分布联系起来。如果生育力数据比其他人已经收集到的高温死亡数据更能预测物种在自然界中发现的气候，那么我们就会知道，雄性生育力确实会影响物种在自然界中的生存。我们也应该开始能够预测它对哪些群体特别重要。例如，我们可能会发现，雄性在其一生中多次交配的物种，雄性通常具有较大的睾丸并产生大量精子，可能在极端温度下能够更好地保持生育能力。雄性在一生中通常只交配几次的物种很容易不育。另外，局限于温度变化很小的地区（如雨林）的物种可能特别容易受到极端温度的影响，而经常遇到快速变化的温度的物种即使在极端条件下也可能保持肥沃。

The climate is warming, and this is predicted to result in an increase in extremes of temperatures. Understanding how this will affect the survival and distribution of organisms is vital if we are to prevent massive losses of species, and invasion by harmful pests. The impacts of climate change are often estimated by examining the temperatures that kill animals. However, this may be flawed. In most animals, from beetles to birds to badgers, males typically lose their fertility at a far lower temperature than that required to kill them. If increasing temperatures cause all the males in a population to become sterile, then that population will not survive, even if the temperatures are nowhere near high enough to actually kill any animals. Unfortunately, there has been very little systematic investigation of this, so we do not know whether this possible impact of increasing temperatures on male fertility really is likely to be a threat to nature.We will rectify this situation by examining the impact of ecologically relevant high temperatures on fertility in male Drosophila fruit flies. We focus initially on a model species, D. pseudoobscura, to provide a detailed examination of how temperature impacts on fertility. We will determine the impact of high temperature and extreme temperature shocks on male fertility, and whether cooler night time temperatures can restore fertility. In many insects and reptiles, after mating with a male, females may store sperm for weeks, months or even years. In some cases the females are better at maintaining the sperm at extreme temperatures than the males are, as male insects of many species often die quicker than females in harsh environments. We will examine whether female sperm storage can ameliorate the impacts of temperature on male fertility. Most importantly, this study on D. pseudoobscura will allow us to work out standard techniques to evaluate these impacts of temperature on male fertility generally. With the knowledge gained from this case study, we will then examine how temperature impacts on fertility in a panel of 50 Drosophila species, carefully chosen to cover a range of lifestyles, habitats and temperatures, including tropical species, temperate species, and species that have spread worldwide. Most importantly, all these species are really well known, with excellent data about the climates they live in, and the temperatures they can survive in the laboratory. We will work out the fertility impacts in all 50 species, and then be able to correlate this with the distributions of the species. If the fertility data predicts the climates where the species are found in nature better than the high temperature fatality data other people have already collected, then we will know that male fertility really does impact on where species can survive in nature. We should also begin to be able to predict which groups it is particularly likely to be important for. For example, we might find that species where males mate many times in their lives, in which males typically have large testes and produce huge numbers of sperm, may be better able to remain fertile at extreme temperatures. Species where males typically mate only a few times in their lives may easily be rendered infertile. Alternatively, species restricted to areas where temperatures vary very little (such as rainforests) may be particularly vulnerable to temperature extremes, whereas species that regularly encounter rapidly changing temperatures may remain fertile even in extreme conditions.