Over recent decades, many Mediterranean and Ponto-Caspian aquatic invertebrate species have dispersed northwards and established as non-native species in colder regions. We hypothesized that these species have cold-tolerant traits, which facilitate dispersal into colder climates. Thanks to these traits, Southern European aquatic species are able to cross biogeographic boundaries. We downloaded the list of all alien invertebrate species that were fully aquatic (i.e. lacking terrestrial adults) from the GRIIS database and picked out those Mediterranean and Ponto-Caspian species that have undergone northwards range expansion. We identified traits that may facilitate dispersal to colder climates including the following: small size; capacity for behavioural thermoregulation; feeding habit (omnivorous, filter-feeders, food generalists); quiescence and dormancy (or diapause); freezing avoidance (presence of cryoprotectants); tolerance to low temperatures or eurythermicity; active dispersal; and enhanced reproduction. We statistically tested the null hypotheses that Mediterranean and Ponto-Caspian alien aquatic invertebrate species that dispersed into the north have all of these traits. We used contingency tables populated with raw frequency data with χ²—tests and assessed statistical significance at α of 0.05. We identified 95 Mediterranean and Ponto-Caspian alien aquatic invertebrate species that have shown northwards range extension, 10 (10%) of which were of Mediterranean origin and 85 (90%) of Ponto-Caspian origin. We found that this northwards dispersal from Southern Europe is mainly limited to a few following groups of aquatic invertebrates: small crustaceans, molluscs, cnidarians and annelids. Ability to go to diapause, hibernation or resting period, temperature tolerance and small size were the traits most commonly shared by these organisms. We conclude that Mediterranean and Ponto-Caspian aquatic invertebrate species showing northwards range expansion have cold-tolerant strategies. The traits analysed can favour the establishment of the species.

近几十年来，许多地中海和 Ponto-Caspian 水生无脊椎动物物种已向北分散，并在较冷的地区建立为非本地物种。我们假设这些物种具有耐寒性状，有助于分散到较冷的气候中。由于这些特征，南欧水生物种能够跨越生物地理边界。我们从 GRIIS 数据库下载了所有完全水生（即缺乏陆生成虫）的外来无脊椎动物物种列表，并挑选了那些经历了向北范围扩张的地中海和 Ponto-Caspian 物种。我们确定了可能有助于向寒冷气候传播的特征，包括：小尺寸；行为体温调节能力；进食习惯（杂食性、滤食性、食物通才）；静止和休眠（或滞育）；避免冷冻（存在冷冻保护剂）；对低温或极热的耐受性；主动分散；和增强的繁殖。我们对分散到北部的地中海和 Ponto-Caspian 外来水生无脊椎动物物种具有所有这些特征的无效假设进行了统计测试。我们使用了用原始频率数据填充的列联表χ ² — 检验和评估 α 为 0.05 的统计显着性。我们确定了 95 个地中海和 Ponto-Caspian 外来水生无脊椎动物物种，它们的范围向北扩展，其中 10 个（10%）来自地中海，85 个（90%）来自 Ponto-Caspian。我们发现，从南欧向北扩散主要限于以下几类水生无脊椎动物：小型甲壳类动物、软体动物、刺胞动物和环节动物。能够进入滞育、冬眠或休息期、温度耐受性和小尺寸是这些生物最常见的特征。我们得出结论，显示向北范围扩张的地中海和蓬托-里海水生无脊椎动物物种具有耐寒策略。分析的特征可以有利于物种的建立。