Potamon fluviatile as well as on the island of Sicily. Although it used to be found as far north as Lake Garda, "P. fluviatile" no longer occurs north of the River Po. In 1997 a population of "P. fluviatile" was discovered under the ruins of Trajan's Forum in the heart of Rome, living in canals built by the Etruscans which connect to the "Cloaca Maxima". Based on a genetic analysis, which demonstrated that these crabs were similar to those in Greece, researchers believe that they had been brought by the Greeks before the founding of the city, some 3000 years ago. The
Potamon fluviatile six "nationes", or "tribes". Natio "fluviatilis" was found in northern Italy, natio "tarantium" in southern Italy, and nationes "thessalonis", "kühnelti" and "laconis" were found in parts of Greece. The geographical distribution of natio "leucosis" was not reported, and it was suggested that a further (undescribed) tribe inhabited the Greek island of Andros. Despite this wealth of infraspecific taxa, they are rarely used by scientists, and some have questioned directly the value of defining infraspecific taxa within "P. fluviatile". In 1990, the population on Malta was described as a separate subspecies, "Potamon fluviatile lanfrancoi", and that taxon has become a conservation