The white-clawed crayfish A. pallipes has suffered in recent decades a strong decline throughout its entire distributional range, mainly due to the growing number of threats coming from anthropic influence, including habitat loss and degradation, overfishing, infectious diseases, and the introduction of non-indigenous crayfish species (NICS). The species is included in the red list of the IUCN (International Union for Conservation of Nature) as a species at risk of extinction. An important goal in conservation biology is to assess the genetic variability and thus the “genetic health” of populations and to identify any evolutionarily significant unit (ESU) within endangered species, before management decisions are taken.
Within RARITY (http://www.life-rarity.eu), a LIFE project for the eradication of the invasive Louisiana red swamp (Procambarus clarkii) and for the preservation of the native white-clawed crayfish in Friuli Venezia Giulia (NE Italy), I was responsible for the genetic characterization of A. pallipes complex in this area, in order to define the taxonomic status, the genetic variability and the population structure and differentition. The analysis of two mitochondrial genes (COI and 16 rDNA) of about 500 individuals from 58 monitored sites showed that the FVG crayfish belong to the A. italicus species, with two different subspecies present: A.i. carsicus and A.i.meridionalis. The analysis at six polimorphic microsatellite loci revealed generally low levels of within population genetic diversity (0,0 <Ho< 0,5) with overall high inbreeding coefficients (average F=0,422), likely as a result of genetic drift in small sized populations. FVG populations appeared significantly differentiated among the different river drainages and were highly structured within rivers displaying a significant pattern of isolation by distance, suggesting significant habitat fragmentation of steam ecosystems.
The combination of mithocondrial and microatellite markers allowed us to identify two ESUs , corresponding to the two subspecies in northern and southern FVG (Rosandra stream). Our data also support the maintenance of separate of separate demographic management strategies for crayfish inhabiting different drainage systems. This study provided new knowledge on white-clawed crayfish populations to create “genetic maps” that can be used as valuable data for restocking practices and conservation programs in FVG.
