Colonization history and human translocations explain the population genetic structure of the noble crayfish (Astacus astacus) in Fennoscandia: Implications for the management of a critically endangered species

Abstract

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.

Money Kills Native Ecosystems: European Crayfish as an Example

“…In the same way, claims have been made that A. astacus was introduced into Sweden during the 1500s by the kings. Later genetic studies have shown that A. astacus has inhabited Swedish aquatic ecosystems since the last ice age, thus being native to Sweden (Edsman et al, 2002;Gross et al, 2013;Dannewitz et al, 2021). Similarly, A. pallipes has been claimed to have been introduced to Spain from Italy only in the 1500s (Clavero et al, 2016), despite genetic evidence dating the species origin on the Iberian Peninsula from the last glaciation (Matallanas et al, 2011(Matallanas et al, , 2016Jelić et al, 2016;Martín-Torrijos et al, 2021a).…”

Soil-Related Predictors for Distribution Modelling of Four European Crayfish Species

“…Fragmentation was proved to be one of the main issues in the long run of protecting sensitive species, even in the context of protected areas that may offer appropriate local conditions but failed in ensuring connectivity between populations [31]. Probably one of the most impacting phenomena, the dominance of invasive alien species [32][33][34][35][36][37], accompanied by the carried deadly disease known as crayfish plague [38][39][40], led to dramatic changes in the distributions of European indigenous crayfish species in the last decades [38]. Modern conservation actions should consider an extensive array of factors that should be monitored and controlled.…”

Editorial: Conservation of European Freshwater Crayfish

“…The authors suggest that current conservation and management programs should consider three phylogeographic groups as essential management units in order to preserve the remaining genetic diversity, which is critically threatened by crayfish plague (Martín-Torrijos et al, 2019). It has been shown for many crayfish species that there are significant differences regarding the genetic diversity across Europe, and that restocking programs should always consider the natural genetic make-up of the populations (e.g., Schrimpf et al, 2014Schrimpf et al, , 2017Lovrenčić et al, 2020;Dannewitz et al, 2021). For restocking purposes, conservationists rely on efficient crayfish breeding systems.…”