Discovering the Pandora's box: the invasion of alien flatworms in Italy.
Alien land planarians have been scarcely recorded in Italy and the aim of this work was to update the distribution of alien planarians in Italy using a citizen science and, whenever possible, a molecular approach. We received 133 records of at least 15 species (Anisorhynchodemus cf. signata, Australopacifica atrata, Australoplana cf. sanguinea alba, Bipalium kewense, B. vagum, Caenoplana cf. dendyi, C. cf. decolorata, C. coerulea, C. variegata, Diversibipalium multilineatum, Diversibipalium "black", Endeavouria septemlineata, and Obama nungara) and some undescribed or unidentifiable-to-species taxa. Records came from all Italian regions except for those characterized by the lowest human population densities (Valle d'Aosta, Molise, and Basilicata) and 83% of records come from private gardens. Most records have been observed in spring and early autumn and seem to increase with increasing rainfall. Citizen-science data significantly expanded the distribution area of these species in Italy, and thus the citizen-science platforms represent an effective tool for the early detection of these alien pest species.