Selfish genetic elements and population viability: the impact of temperature and sexual selection

气候变化正在加速。许多种群预计将灭绝，因为它们无法对不断变化的环境做出足够快的反应。我们对种群在多大程度上有能力进化以应对温度变化知之甚少。苍蝇种类提供了很多关于野外环境变化的潜在适应性的信息。这在很大程度上是因为他们的一些基因包含在紧密相连的群体中（倒置），这些群体总是一起遗传，并作为一个整体代代相传。这样就可以量化这些锁定染色体区域内基因频率的变化，这些变化与温度等环境因素的变化有关。这些基因的任何变化都只能归因于进化。许多种群都有自私的遗传元素（SGEs），这些基因不公平地偏向遗传，以增加它们在种群中的传播。尽管有这种传播优势，但许多sge在自然种群中是短暂的，或者以低于预期的频率发现。目前尚不清楚是什么因素调控了野生SGEs。我们将研究温度变化对果蝇中自私基因频率的影响（存在于反转中），该基因导致雌性种群性别比例偏倚，因此可能导致由于缺乏雄性而导致种群灭绝。这种性别比例扭曲的频率在美国西北部已经稳定了70年，但在人群中观察到的梯度的潜在原因仍然未知。我们将通过温度梯度量化自然种群中性别比例扭曲基因频率的变化。一种可能性是，雌性交配行为的变化可能直接调节了性别比驱动的频率。我们发现，雌性多次交配可以显著降低实验室种群中性别比例扭曲基因的频率。这是由于携带性别比基因的男性与不携带性别比基因的男性相比，精子竞争能力较差。我们将评估温度在改变野生雌性交配频率方面的重要性，从而评估携带性比基因的雄性所遇到的精子竞争水平。我们预测低温对性别比雄性不利，因为雌性在低温下寿命更长，交配频率更高，因此精子竞争水平更高，减少了性别比雄性的父权，阻碍了它们的传播。这项研究将提供有关种群适应不断变化的环境的能力的宝贵信息。这可能提供重要信息，说明哪些物种可能成为潜在的农业害虫和疾病媒介，而其他物种则有灭绝的危险。通过强调雌性交配频率与不利/有利基因传播之间的联系，它还将对圈养繁殖计划和生物控制计划具有价值。

Climate change is proceeding apace. Many populations are predicted to go extinct, unable to respond rapidly enough to their changing environment. We have little understanding about the extent to which populations have the ability to evolve in response to changing temperatures. Fly species have provided much needed information about potential adaptation to environmental changes in the wild. This is largely because some of their genes are contained in tightly linked groups (inversions) that are always inherited together and passed down as a unit through the generations. This allows quantification of changes in the frequencies of genes contained within these locked chromosomal regions in relation to changing environmental factors such as temperature. Any change in these genes can only be attributed to evolution. Many populations harbour selfish genetic elements (SGEs), genes that unfairly bias inheritance to increase their spread in a population. In spite of this transmission advantage, many SGEs are transient in natural population or found at lower than expected frequencies. It is not clear what factors regulate SGEs in the wild. We will examine the impact of temperature variation on the frequency of a selfish gene (present within an inversion) in a fruit fly that cause female biased population sex ratios, and hence may cause population extinction due to lack of males. The frequency of this sex ratio distorter has remained stable for >70 years in the Northwestern USA, but the underlying reason for the observed gradient among populations remains unknown. We will quantify changes in the frequency of the sex ratio distorting gene in natural populations across a temperature gradient. One possibility is that changes in female mating behaviour may directly regulate the frequency of sex ratio drive. We have found that female multiple mating can dramatically reduce the frequency of sex ratio distorting genes in lab populations. This is due to the poor sperm competitive ability of males carrying the sex ratio gene compared to non-carrying males. We will evaluate the importance of temperature in altering female mating frequencies in the wild and therefore the level of sperm competition encountered by males carrying the sex ratio gene. We predict that low temperatures are unfavourable to sex ratio males because females live longer and may mate more frequently at lower temperature and hence the level of sperm competition is greater, reducing the paternity of sex ratio males barring their spread. This research will provide valuable information about the ability of populations to adapt to changing environments. This may provide important information about which species may turn into potential agricultural pests and disease vectors, whereas other species risk going extinct. It will also be of value to captive breeding programmes and in biological control schemes by highlighting the link between female mating frequency and the spread of unfavourable/favourable genes.