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Endangered genetic diversity of the stone crayfish and noble crayfish revealed by DNA barcoding and species distribution modelling

The stone crayfish (Austropotamobius torrentium) and noble crayfish (Astacus astacus) are native European freshwater species with significant population declines caused by anthropogenic pressure on their habitats, invasive crayfish species, and climate change. In order to develop effective conservation for these threatened species, prerequisite is, among others, a sound knowledge of their genetic diversity patterns. The aim of this research was to assess genetic diversity of both native species in the freshwater habitats of Croatia using DNA barcoding based on sequencing a short fragment of the mtDNA cytochrome c oxidase subunit I (COI) gene. In addition, species distribution modelling was used to reveal the impact of ongoing climate change on their genetic diversity. Overall, 392 sequences were obtained for these two species from the study area (118 for the stone crayfish and 274 for the noble crayfish). Phylogenetic reconstruction revealed the existence of high genetic diversity within stone crayfish, maintained in seven distinct mtDNA phylogroups (containing 45 unique COI Croatian haplotypes). Since those geographically and genetically isolated phylogroups are highly relevant for conservation due to their evolutionary distinctiveness and restricted distribution, we declared them as distinct evolutionary significant units. Results for the noble crayfish showed that all Croatian haplotypes belong to two previously discovered genetic lineages, with the indication of a novel lineage (containing 16 unique COI Croatian haplotypes). Overlapping genetic data with potential future distribution of these two keystone species revealed their vulnerability ; most of the populations with high and/or unique genetic diversity are located in the areas predicted to become unsuitable, and consequently have a high probability of being lost in the future. DNA barcoding proved to be a useful tool for studying species genetic diversity and guiding their conservation. Considering ongoing climate extremes and predictions, prompt actions should take place in order to preserve the existing diversity.

Austropotamobius torrentium, Astacus astacus, Croatia, freshwaters, mtDNA

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