Anecdotally, it seems as though species of fauna and flora introduced to England and Wales during the Roman occupation are still more likely to be found near Roman settlements. Obviously, some introduced species, such as the rabbit, are now extremely widespread. But, for example Alexanders was introduced as a food plant, and still grows in profusion around Richborough Castle, the former Roman fort of Rutupiae. I have only ever seen the edible Roman snail in England in the grounds of a former Roman villa.
Has anyone studied this to see if there's actually a statistically significant correlation, 1,600 years on?