Data from: Climate-associated tundra thaw pond formation and range expansion of boreal zooplankton predators

Most of the freshwater component of the Earth's surface is composed of shallow tundra ponds. These high latitude ecosystems have been exposed to a variety of abiotic disturbances associated with recent environmental change. However, the biological significance of these changes remains poorly understood. Here, we characterize the abiotic disturbance to the shallow tundra ponds of northwest Alaska. We used historical aerial imagery to determine that up to 53% of the sampled ponds have formed during the recent warmer decades (since the 1970s). We discovered that two top predator species (phantom midges of the genus Chaoborus) of the freshwater zooplankton have recently undergone range expansion, forming widespread (a scale of hundreds of km) stable tundra populations. We assessed the population persistence of these boreal predators by longitudinal sampling over 14 yr. Recent thaw ponds had significantly dissimilar zooplankton communities to communities of ponds that formed before 1950. Both predator and herbivore species differed by age of pond. Younger pond ages and warmer surface temperatures were the significant predictors of the presence of temperate Chaoborus americanus in tundra ponds. Ponds containing tundra populations of C. americanus and C. cf. flavicans were associated with recent formation (83–90%). Recent ponds in river valleys appeared more important than recent ponds near roads as colonization corridors for C. americanus. Only 24% of the tundra keystone predator, Heterocope septentrionalis, populations were from recent ponds. Our results suggest that climate-associated disturbance can lead to a widespread stable range expansion of boreal species despite the propinquity of older ponds with top-down control exerted by an endemic keystone predator.

地球表面的淡水主体多由浅生苔原池塘（shallow tundra ponds）构成。这类高纬度生态系统正遭受着与近期环境变化相关的多种非生物扰动（abiotic disturbances），但学界对这些变化的生物学意义仍知之甚少。本研究针对阿拉斯加西北部的浅生苔原池塘的非生物扰动展开系统性表征。我们借助历史航空影像分析发现，在采样的池塘中，多达53%是自20世纪70年代以来的气候变暖时段内形成的。
研究发现，淡水浮游动物中的两类顶级捕食者——幽蚊属（Chaoborus）幽蚊——近期发生了分布范围扩张，形成了覆盖数百公里尺度的稳定苔原种群。我们通过14年的纵向采样，评估了这些北方捕食者的种群存续情况。与1950年前形成的池塘相比，近期形成的融冻池塘（thaw ponds）的浮游动物群落结构存在显著差异。捕食者与植食性动物的群落组成均随池塘形成年限呈现差异。池塘形成年限更短、表层水温更高，是温带美洲幽蚊（Chaoborus americanus）在苔原池塘中出现的显著预测因子。
栖息有美洲幽蚊苔原种群及黄褐幽蚊近缘种（Chaoborus cf. flavicans）的池塘，多为近期形成（占比83%~90%）。对于美洲幽蚊而言，河谷中的近期形成池塘，相比道路周边的同类池塘，是更关键的定殖扩散廊道。苔原关键捕食者北方异肢水蚤（Heterocope septentrionalis）的种群中，仅有24%来自近期形成的池塘。本研究结果表明，尽管毗邻由地方性关键捕食者实施下行调控（top-down control）的老旧池塘，但与气候相关的扰动仍可推动北方物种实现大范围且稳定的分布范围扩张。