Here we present a new eastern Baltic Chironomidae training set (TS) containing 35 sites that was collected and merged with neighbouring published Finnish (82 lakes) and northern part of the Polish (nine lakes) TSs. Chironomidae, non‐biting midges, are known to be strongly responsive to the July air temperature and are widely used to infer palaeotemperature. Several modern analogue‐based TSs necessary for calibrating the relationships between mean July air temperature (MJAT) and chironomids are available for Europe. However, none of these is representative of the transitional climate typical for eastern Baltic (Estonia, Latvia, Lithuania). The Finno–Baltic–Polish TS contains 121 sites and covers a geographically continuous 70–50°N latitudinal and 7 °C (12.1–19.2 °C) MJAT gradient. Canonical correspondence analysis revealed that, among the tested environmental variables (pH, water depth, dissolved oxygen, MJAT), the MJAT explains the highest amount of variation, both for the eastern Baltic separately and the Finno–Baltic–Polish TSs. The weighted averaging–partial least squares‐based cross‐validation test reveals that the Finno–Baltic–Polish TS has a low root mean square error of prediction (0.7 °C) confirming the high reliability of the TS. The temperature optima of the taxa included in the new Finno–Baltic–Polish TS and widely used Swiss–Norwegian TS were examined. The observed dissimilarities can be attributed to the differences in the temperature ranges represented by the TS, the taxonomic identification level, the general cosmopolitan taxa distribution patterns and the influence of TS‐specific geographic position, climatic or environmental conditions. The new Finno–Baltic–Polish TS adds to the knowledge on the modern distribution of Chironomidae taxa and widens the geographical area of reliable Chironomid‐based MJAT reconstructions into the eastern European lowland.

中文翻译：

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基于摇蚊科的波罗的海东部地区七月平均气温重建推理模型

在这里，我们提出了一个新的波罗的海东部摇蚊科训练集 (TS)，其中包含 35 个站点，这些站点是收集并与邻近已发布的芬兰（82 个湖泊）和波兰北部（9 个湖泊）TS 合并的。摇蚊科（不咬人的蠓）对七月气温有强烈反应，被广泛用于推断古气温。欧洲可以使用几种基于模拟的现代 TS 来校准七月平均气温 (MJAT) 和摇蚊之间的关系。然而，这些都不能代表波罗的海东部（爱沙尼亚、拉脱维亚、立陶宛）典型的过渡气候。芬兰-波罗的海-波兰 TS 包含 121 个站点，覆盖地理上连续的 70-50°N 纬度和 7°C (12.1-19.2°C) MJAT 梯度。规范对应分析显示，在测试的环境变量（pH、水深、溶解氧、MJAT）中，MJAT 解释了波罗的海东部和芬兰-波罗的海-波兰 TS 的最高变化量。基于加权平均-偏最小二乘法的交叉验证测试表明，芬兰-波罗的海-波兰 TS 的预测均方根误差较低 (0.7 °C)，证实了 TS 的高可靠性。对新的芬兰-波罗的海-波兰 TS 和广泛使用的瑞士-挪威 TS 中包含的类群的最适温度进行了检查。观察到的差异可归因于 TS 所代表的温度范围、分类鉴定水平、一般世界性分类群分布模式以及 TS 特定地理位置、气候或环境条件的影响的差异。新的芬兰-波罗的海-波兰 TS 增加了关于摇蚊科类群现代分布的知识，并将可靠的基于摇蚊的 MJAT 重建的地理区域扩大到东欧低地。