Data from: Ecological speciation by temporal isolation in a population of the stonefly Leuctra hippopus (Plecoptera, Leuctridae)

Stream dwelling invertebrates are ideal candidates for the study of ecological speciation as they are often adapted to particular environmental conditions within a stream and inhabit only certain reaches of a drainage basin, separated by unsuitable habitat. We studied an atypical population of the stonefly Leuctra hippopus at a site in central Norway, the Isterfoss rapids, in relation to three nearby and two remote conspecific populations. Adults of this population emerge about a month earlier than those of nearby populations, live on large boulders emerging from the rapids, and are short-lived. This population also has distinct morphological features and was studied earlier during the period 1975–1990. We reassessed morphological distinctness with new measurements and added several analyses of genetic distinctness based on mitochondrial and nuclear sequence markers, as well as AFLP fingerprinting and SNPs mined from RAD sequences. The Isterfoss population is shown to be most closely related to its geographical neighbors, yet clearly morphologically and genetically distinct and homogeneous. We conclude that this population is in the process of sympatric speciation, with temporal isolation being the most important direct barrier to gene flow. The shift in reproductive season results from the particular temperature and water level regime in the Isterfoss rapids. The distinct adult body shape and loss of flight are hypothesized to be an adaptation to the unusual habitat. Ecological diversification on small spatial and temporal scales is one of the likely causes of the high diversity of aquatic insects.栖息于溪流的无脊椎动物是生态物种形成（ecological speciation）研究的理想对象，因为它们通常适配溪流内的特定环境条件，且仅栖息于流域内被不适宜生境分隔的特定河段。我们以挪威中部伊斯特福斯急流（Isterfoss rapids）区域的异常种群——石蝇Leuctra hippopus为研究对象，并以附近的3个以及偏远的2个同种种群作为对照。该种群的成虫羽化时间较邻近种群早约1个月，栖息于急流中露出的大型砾石之上，且成虫寿命极短。该种群还具备独特的形态特征，且曾在1975至1990年间被前人研究过。我们通过新增测量数据重新评估了该种群的形态独特性，并基于线粒体与细胞核序列标记、扩增片段长度多态性（Amplified Fragment Length Polymorphism, AFLP）指纹图谱以及从限制性位点相关DNA（Restriction-site Associated DNA, RAD）序列中挖掘得到的单核苷酸多态性（Single Nucleotide Polymorphism, SNPs）开展了多项遗传差异性分析。研究结果显示，伊斯特福斯种群与地理邻近种群的亲缘关系最近，但在形态与遗传层面均表现出显著的独特性且内部同质化程度高。我们据此推断，该种群正处于同域物种形成（sympatric speciation）过程中，其中时间隔离（temporal isolation）是阻碍基因流（gene flow）的最关键直接屏障。其繁殖季的转变源于伊斯特福斯急流独特的温度与水位情势。成虫独特的躯体形态与飞行能力丧失，被推测为对该特殊生境的适应性演化。在较小空间与时间尺度上发生的生态分化，是水生昆虫物种多样性极高的潜在成因之一。