1. Cladocera serve as important bio‐ and paleo‐indicators of lake food webs and environmental conditions. The ecological optima of cladocerans are often established by regional‐scale calibration sets, with subsequent comparisons to limnological variables. However, due to logistical constraints when sampling large numbers of lakes, this approach often limits the length of the environmental gradients that can be examined. To extend spatial and limnological gradients, we combined 20 datasets (388 lakes) containing both cladoceran and environmental data, spanning multiple ecoregions across Canada and Alaska. These data were collected over c. 20 years using similar techniques in a single laboratory. Our continental‐scale analysis examined the main chemical and physical variables that influenced cladoceran assemblages, and identified critical environmental thresholds structuring assemblages.
2. Multivariate analyses were used to examine the influences of six environmental variables (depth [either maximum depth or coring depth, which are very similar], surface area, pH, calcium [Ca], total phosphorus [TP], and dissolved organic carbon) and ecoregion classifications on cladoceran assemblages. Gradients of pH and Ca were strongly related. Daphnia longispina spp. and Chydorus brevilabris/biovatus were associated with higher pH and Ca concentrations, while Bosmina spp. and Holopedium spp. were more common in lakes with lower pH and Ca. Dissolved organic carbon was highly correlated with TP. Chydorus brevilabris/biovatus was associated with higher‐nutrient systems. Littoral chydorids, D. longispina spp., Holopedium spp., and Daphnia pulex spp. were associated with intermediate TP and dissolved organic carbon concentrations, and Bosmina spp. was more closely associated with oligotrophic systems.
3. Physical limnological variables influenced taxonomic composition on a continental scale. For example, D. longispina spp., D. pulex spp., Bosmina spp., and Holopedium spp. were associated with larger and/or deeper systems, and littoral chydorids were associated with smaller and/or shallower lakes. A multivariate regression tree identified two thresholds important for structuring assemblages based on pH (<7 and ≥7, probably closely tied to lakewater Ca concentrations) and depth (<6.45 m and ≥6.45 m at pH < 7, and <4.75 m and ≥4.75 m at pH ≥ 7).
4. Our results highlight the sensitivity of several cladoceran taxa to multiple chemical and physical gradients. We demonstrate that the ecological responses of cladocerans to environmental variables—often established through regional‐scale surveys—are applicable across ecoregions and broad limnological gradients, reinforcing the value of cladocerans as bioindicators of key chemical and physical variables in freshwaters and as paleoindicators for assessing human impacts on aquatic systems through time.

中文翻译：

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大陆范围内锁骨群落的环境驱动因素：阿拉斯加和加拿大数据集的综合

1. Cladocera是湖泊食物网和环境条件的重要生物和古生物指示剂。锁骨藻的生态最佳化通常是通过区域规模的校准集来确定的，并随后与植物学变量进行比较。但是，由于对大量湖泊进行采样时的后勤限制，这种方法通常会限制可以检查的环境梯度的长度。为了扩展空间和森林学梯度，我们组合了包含锁骨和环境数据的20个数据集（388个湖泊），横跨加拿大和阿拉斯加的多个生态区域。这些数据是通过c收集的。在单个实验室中使用类似技术已有20年了。我们的大陆尺度分析研究了影响枝角cer组合的主要化学和物理变量，并确定了构成组合的关键环境阈值。
2. 多变量分析用于检验六个环境变量（深度[最大深度或取芯深度，非常相似]，表面积，pH，钙[Ca]，总磷[TP]和溶解的有机碳）的影响。锁骨组合的生态区分类。pH和Ca的梯度密切相关。水蚤（Daphnia longispina spp。）短剑藻和短va /生物气与较高的pH和钙浓度有关，而波希米亚菌属（Bosmina spp）。和霍兰氏菌属。在pH和Ca较低的湖泊中更为常见。溶解的有机碳与TP高度相关。短胸/活体与更高养分的系统有关。滨海chydorids，D. longispina属，Holopedium属和蚤状溞属。与中间TP和溶解的有机碳浓度有关，而与Bosmina spp有关。与贫营养系统更紧密相关。
3. 物理语言学变量影响了大陆范围内的生物分类组成。例如，D. longispina属，D.状溞属，象鼻属，和Holopedium属。与较大和/或较深的系统相关联，沿海梭鱼与较小和/或较浅的湖泊相关联。多元回归树根据pH值（<7和≥7，可能与湖水Ca浓度紧密相关）和深度（pH <7时分别为<6.45 m和≥6.45m，<4.75 m和≥ pH≥7时为4.75 m）。
4. 我们的结果强调了几种锁骨分类单元对多种化学和物理梯度的敏感性。我们证明锁骨对环境变量的生态反应（通常通过区域规模的调查确定）适用于整个生态区域和广泛的林学梯度，从而增强了锁骨在淡水中作为关键化学和物理变量的生物指标以及作为评估人类的古指标的价值随着时间的流逝对水生系统产生影响。