Data from: Spatiotemporal dynamics and genome-wide association analysis of desiccation tolerance in Drosophila melanogaster

Water availability is a major environmental challenge to a variety of terrestrial organisms. In insects, desiccation tolerance varies predictably over spatial and temporal scales and is an important physiological determinant of fitness in natural populations. Here, we examine the dynamics of desiccation tolerance in North American populations of Drosophila melanogaster using: 1) natural populations sampled across latitudes and seasons; 2) experimental evolution in field mesocosms over seasonal time; 3) genome-wide associations to identify SNPs/genes associated with variation for desiccation tolerance; and 4) subsequent analysis of patterns of clinal/seasonal enrichment in existing pooled sequencing data of populations sampled in both North America and Australia. A cline in desiccation tolerance was observed, for which tolerance exhibited a positive association with latitude; tolerance also varied predictably with culture temperature, demonstrating a significant degree of thermal plasticity. Desiccation tolerance evolved rapidly in field mesocosms, although only males showed differences in desiccation tolerance between spring and autumn collections from natural populations. Water loss rates did not vary significantly among latitudinal or seasonal populations; however, changes in metabolic rates during prolonged exposure to dry conditions are consistent with increased tolerance in higher latitude populations. Genome wide associations in a panel of inbred lines identified twenty-five SNPs in twenty-one loci associated with sex-averaged desiccation tolerance, but there is no robust signal of spatially varying selection on genes associated with desiccation tolerance. Together, our results suggest that desiccation tolerance is a complex and important fitness component that evolves rapidly and predictably in natural populations.

水分可获得性是多种陆生生物面临的一项主要环境挑战。在昆虫中，耐旱性（desiccation tolerance）随空间与时间尺度呈现可预测的变化，是自然种群中影响适合度的重要生理决定因素。本研究针对北美种群的黑腹果蝇（Drosophila melanogaster），通过以下四种方式探究耐旱性的动态变化：1）对不同纬度与季节采集的自然种群进行取样；2）在野外中型实验生态系统中开展跨季节时长的实验进化研究；3）借助全基因组关联分析，筛选与耐旱性变异相关的单核苷酸多态性（SNPs）及基因；4）针对北美与澳大利亚两地采集种群的现有混池测序数据，后续分析其梯度/季节富集模式。
研究观察到耐旱性存在渐变群现象，其耐受水平与纬度呈正相关；同时耐旱性随培养温度呈现可预测的变化，表明其具备显著程度的热可塑性。野外中型实验生态系统中的耐旱性演化速度较快，但仅在雄性个体中观察到自然种群春季与秋季采集样本的耐旱性差异。不同纬度或季节种群的水分流失速率无显著差异；然而，长期暴露于干燥环境时的代谢速率变化，与高纬度种群耐旱性提升的结果一致。对一组近交系开展的全基因组关联分析，在21个基因座中鉴定出25个与不分性别耐旱性相关的单核苷酸多态性，但未在耐旱性相关基因中检测到空间异质性选择的稳健信号。综合来看，本研究结果表明，耐旱性是一项复杂且重要的适合度组成部分，可在自然种群中快速且可预测地演化。