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

气候变化正在快速推进。许多种群预计将灭绝，无法对不断变化的环境做出足够迅速的反应。我们对种群在多大程度上能够随着气温变化而进化知之甚少。苍蝇物种为野生环境变化的潜在适应提供了急需的信息。这在很大程度上是因为它们的一些基因包含在紧密相连的群体(倒位)中，这些群体总是一起遗传，并作为一个单位代代相传。这使得能够量化这些锁定的染色体区域中包含的基因频率随温度等环境因素的变化而发生的变化。这些基因的任何变化都只能归因于进化。许多群体都有自私的遗传元素(SGE)，这些基因不公平地偏向遗传，以增加它们在群体中的传播。尽管有这种传播优势，许多SSE在自然种群中是瞬时的，或者发现的频率低于预期。目前还不清楚是什么因素在野外调节SGE。我们将研究温度变化对果蝇自私基因(存在于倒位中)频率的影响，该基因导致雌性偏向种群性别比，从而可能导致种群因缺乏雄性而灭绝。这种性别比扭曲的频率在美国西北部70年来一直保持稳定，但观察到的人口之间差异的根本原因仍然未知。我们将量化自然种群中性别比扭曲基因在温度梯度上的频率变化。一种可能性是，雌性交配行为的变化可能直接调节性别比驱动的频率。我们发现，在实验室种群中，雌性多次交配可以显著减少性别比扭曲基因的频率。这是由于携带性别比例基因的男性与未携带基因的男性相比，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，从而评估携带性别比例基因的雄性遇到的精子竞争水平。我们预测，低温对性别比雄性不利，因为雌性寿命更长，在较低温度下可能更频繁地交配，因此精子竞争水平更高，从而降低了性别比雄性的父权，阻止了它们的传播。这项研究将提供有关人口适应不断变化的环境的能力的宝贵信息。这可能提供有关哪些物种可能成为潜在的农业害虫和病媒的重要信息，而其他物种则面临灭绝的风险。它还将通过强调雌性交配频率与不利/有利基因传播之间的联系，对圈养繁殖方案和生物防治计划有价值。

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.