Genetic diversity in natural populations of noble crayfish (Astacus astacus L.) in north-western Poland on the basis of combined SSR and AFLP data

Abstract

Background: Conservation of noble crayfish (Astacus astacus) populations is becoming particularly important since the number of individuals is rapidly declining across the distribution range of the species in Europe. Five crayfish populations in northwestern Poland have been constantly monitored for two decades. However, the genetic structure of these populations has not been analysed, although this information is important to devise effective conservation strategies.

Methods: Noble crayfish were collected in the autumn of 2014 by scuba diving in Lakes Graniczne, Babinki, Biwakowe, Sęki and Kwisno, all of which are situated in the Bytów Lakeland of northwestern Poland. Genetic diversity of the five populations was assessed based on allele variability in nine SSR regions and six AFLP primer combinations.

Results: Microsatellite results analysed with AMOVA showed that the diversity between populations corresponds to 18% of total variability, which was confirmed by similar results obtained using AFLP. Additionally, significant genetic diversity was revealed by high average F_ST values. All of the studied crayfish populations significantly deviated from the expected Hardy-Weinberg genetic equilibrium and were characterised by negative values of inbreeding coefficient (F_IS).

Discussion: The invariably negative inbreeding coefficients (F_IS) suggest a low number of mating individuals, a possible consequence of the phenomenon known as genetic bottleneck. However, additional comprehensive analyses are needed to assess the genetic structure, origin and vulnerability of the remaining populations of noble crayfish in the Bytów Lakeland of northwestern Poland, which have high conservation value and are particularly important as a live genetic bank for breeding and restitution purposes.

Keywords: Conservation genetics; Genetic differentiation; Microsatellite marker; Restoration; Species extinction.

Figure 1. The location of sites of examined noble crayfish populations in the Bytów Lakeland.

BI –Biwakowe Lake, KW –Kwisno Lake, GR –Graniczne Lake, SE –Sęki Lake, BA –Babinki Lake.

Figure 2. Principal Coordinates Analysis (PCoA) of the Fst values between studied populations of the noble crayfish.

PCoA of the Fst values calculated between crayfish populations (marked as blue circles) differentiates Se and Ba from Gr and Kw, and Bi.

Figure 3. Unrooted UPGMA clustering of noble crayfish populations based on SSR loci and Nei’s chord distance (1983) (Da) among pairs of populations.

Numbers indicate clades bootstrap support in 1,000 replicates.

Figure 4. Results of the hierarchical STRUCTURE analysis of the five noble crayfish populations under analysis.

K refers to the number of inferred genetic clusters. The black lines separate individuals of different populations.

Figure 5. Unrooted UPGMA clustering of noble crayfish populations based on AFLP loci and Cavalli-Sforza & Edwards (1967) distances among pairs of populations.

Numbers indicate clades bootstrap support above 50% in 1,000 replicates.

Figure 6. Principal Coordinates Analysis (PCoA) of the based on AFLP Cavalli-Sforza & Edwards (1967) distances between analysed populations of the noble crayfish.

Graph represents distances calculated between five crayfish populations (marked as blue circles).