Data from: Signatures of local adaptation along environmental gradients in a range-expanding damselfly (Ischnura elegans)

Insect distributions are shifting rapidly in response to climate change and are undergoing rapid evolutionary change. We investigate the molecular signatures underlying local adaptation in the range-expanding damselfly, Ischnura elegans. Using a landscape genomic approach combined with generalized dissimilarity modelling (GDM), we detect selection signatures on loci via allelic frequency change along environmental gradients. We analyse 13,612 Single Nucleotide Polymorphisms (SNPs), derived from Restriction site-Associated DNA sequencing (RADseq), in 426 individuals from 25 sites spanning the I. elegans distribution in Sweden, including its expanding northern range edge. Environmental association analysis (EAA) and the magnitude of allele frequency change along the range expansion gradient revealed significant signatures of selection in relation to high maximum summer temperature, high mean annual precipitation, and low wind speeds at the range edge. SNP annotations with significant signatures of selection revealed gene functions associated with ongoing range expansion, including heat shock proteins (HSP40 and HSP70), ion transport (V-ATPase) and visual processes (long wavelength-sensitive opsin), which have implications for thermal stress response, salinity tolerance and mate discrimination, respectively. We also identified environmental thresholds where climate-mediated selection is likely to be strong, and indicate that I. elegans is rapidly adapting to the climatic environment during its ongoing range expansion. Our findings empirically validate an integrative approach for detecting spatially explicit signatures of local adaptation along environmental gradients.

受气候变化影响，昆虫的分布范围正快速发生改变，同时亦在经历迅速的演化变迁。本研究以正在扩张分布范围的长叶异痣蟌（Ischnura elegans）为研究对象，探究其本地适应背后的分子特征。我们结合景观基因组学方法与广义相异模型（generalized dissimilarity modelling, GDM），通过等位基因频率沿环境梯度的变化，检测位点上的选择信号。我们对瑞典境内覆盖长叶异痣蟌分布范围（包含其正在扩张的北部分布边界）的25个采样点的426个个体进行分析，共获得13612个单核苷酸多态性（Single Nucleotide Polymorphisms, SNPs）位点，这些位点源自限制性酶切位点相关DNA测序（Restriction site-Associated DNA sequencing, RADseq）。环境关联分析（Environmental association analysis, EAA）以及沿分布扩张梯度的等位基因频率变化幅度分析显示，存在与夏季最高温偏高、年平均降水量偏高以及分布边界处风速偏低相关的显著选择信号。对携带显著选择信号的SNP进行注释后，发现其相关基因功能与当前的分布扩张过程相关，包括热休克蛋白（heat shock proteins, HSP40和HSP70）、离子转运（V-ATPase）以及视觉通路（长波长敏感视蛋白，long wavelength-sensitive opsin），分别对应热应激响应、盐度耐受以及配偶识别。我们还确定了气候介导选择作用较强的环境阈值，并表明长叶异痣蟌在当前的分布扩张过程中，正快速适应其所处的气候环境。本研究结果实证验证了一种可用于检测沿环境梯度的空间显性本地适应信号的整合方法。