1. The noble crayfish (Astacus astacus) is an endangered freshwater species in Europe. The main threat is from lethal crayfish plague, caused by the oomycete Aphanomyces astaci that has been spread over Europe by introduced North American crayfish species, acting as chronic carriers of the disease.
2. Most of the remaining noble crayfish populations are found in the Baltic Sea area, and there is an urgent need to implement conservation actions to slow down or halt the extinction rate in this region. However, limited knowledge about the genetic structure of populations in this area has so far precluded the development of conservation strategies that take genetic aspects into consideration.
3. Key objectives of this large-scale genetic study, covering 77 locations mainly from northern Europe, were to describe the contemporary population genetic structure of the noble crayfish in the Fennoscandian peninsula (Sweden, Norway, and Finland), taking postglacial colonization history into account, and to evaluate how human activities such as stocking have affected the genetic structure of the populations.
4. Analyses of 15 microsatellite markers revealed three main genetic clusters corresponding to populations in northern, middle, and southern Fennoscandia, with measures of genetic diversity being markedly higher within populations in the southern cluster. The observed genetic structure probably mirrors two main colonizations of the Baltic Sea basin after the last glaciation period. At the same time, several deviations from this pattern were observed, reflecting past human translocations of noble crayfish.
5. The results are discussed in relation to the conservation and management of this critically endangered species. In particular, we recommend increased efforts to protect the few remaining noble crayfish populations in southern Fennoscandia and the use of genetic information when planning stocking activities, such as reintroductions following local extinctions.

中文翻译：

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殖民历史和人类易位解释了芬诺斯坎迪亚贵族小龙虾 (Astacus astacus) 的种群遗传结构：对极度濒危物种管理的影响

1. 贵族小龙虾（Astacus astacus）是欧洲濒临灭绝的淡水物种。主要威胁来自致命的小龙虾瘟疫，由卵菌Aphanomyces astaci引起，该菌是由引入的北美小龙虾物种传播到欧洲，作为疾病的慢性携带者。
2. 大多数剩余的贵族小龙虾种群都在波罗的海地区发现，迫切需要实施保护行动以减缓或阻止该地区的灭绝速度。然而，迄今为止，由于对该地区种群遗传结构的了解有限，因此无法制定考虑遗传因素的保护策略。
3. 这项大规模遗传研究的主要目标是涵盖主要来自北欧的 77 个地点，其主要目标是描述芬诺斯坎迪亚半岛（瑞典、挪威和芬兰）的贵族小龙虾的当代种群遗传结构，同时考虑到冰后殖民历史，并评估放养等人类活动如何影响种群的遗传结构。
4. 对 15 个微卫星标记的分析揭示了三个主要的遗传簇，分别对应于芬诺斯坎迪亚北部、中部和南部的种群，南部种群中遗传多样性的测量值明显更高。观察到的遗传结构可能反映了末次冰河期后波罗的海盆地的两个主要定居点。同时，观察到与这种模式的一些偏差，反映了过去人类对高贵小龙虾的易位。
5. 讨论结果与这种极度濒危物种的保护和管理有关。特别是，我们建议加大力度保护芬诺斯坎迪亚南部仅存的少数贵族小龙虾种群，并在计划放养活动时使用遗传信息，例如在当地灭绝后重新引入。