Analyses of rare collection samples as conservation tool for the last known Italian population of Graphoderus bilineatus (Insecta: Coleoptera)

Graphoderus bilineatus is a predacious diving beetle, widely distributed across Europe. Its poor dispersal ability and the fragmentation and deterioration of its habitats have been indicated as the major causes of decline. In several western European countries, the species is extinct, justifying its inclusion as "vulnerable" in the IUCN red list. Aiming for the conservation of the last known population of G. bilineatus in the northern Italian region of Emilia Romagna, at the lake Pratignano, we surveyed its genetic diversity at the mitochondrial COI gene and compared it to that of other European populations. Two fixed COI haplotypes were found in the Italian and Austrian populations, respectively. Both haplotypes were unique among the European populations surveyed, suggesting these populations suffered a bottleneck and geographic isolation. Populations in western Europe showed lower genetic diversity and higher degree of differentiation than eastern populations. The uniqueness of Pratignano haplotype makes it difficult to choose a source population from which to transfer animals for a possible restocking. Selection of the source population should be based mainly on ecological considerations, but at the same time ensuring a good genetic diversity to maximize the adaptive potential.