ABSTRACT This study investigates the phylogeography of the endangered European White‐Clawed Crayfish (WCC) Austropotamobius pallipes species complex in the main tributaries of the Po River basin in southern Switzerland and northern Italy, a diversity hotspot for this species. Because of various factors, including invasive species and pathogens, this keystone species experienced a significant decline. Conservation efforts should be taken to protect the species, but there is a lack of basic knowledge about the diversity and distribution of remaining WCC populations. We used mitochondrial (COI, 12S, 16S) and nuclear (28S) markers, generating, to our knowledge, the most comprehensive multiple‐marker dataset for this species, an essential step toward resolving the taxonomic puzzle surrounding the WCC. All samples collected in Canton Ticino belonged to the subspecies A. f. fulcisianus , with 14 unique COI haplotypes, none of which were previously documented. Phylogenetic analyses revealed close genetic ties to Italian populations, supporting theories of northward expansion from the Italian peninsula. High haplotype diversity was observed in the southernmost area of Canton Ticino, where waters from three major tributaries of the Po River (Adda, Olona‐Seveso‐Lambro system and Ticino) flow near each other. In contrast, northern WCC populations showed reduced diversity, likely due to bottlenecks, habitat fragmentation, invasive species and pathogen pressures. Our findings highlight the need for cross‐border management, habitat protection and genetic monitoring to safeguard this keystone species amid ongoing environmental threats. Hence, taking advantage of the local topography and insights gained from this study, we propose establishing ark sites in isolated headwater areas.
Prati et al. (2026) studied this question.