A Field Guide to the Snails of Lord Howe Island

16 Conservation Island species are particularly susceptible to extinction, as shown by examples such as the Dodo. There are several reasons for this vulnerability. First, island species usually have smaller populations than more widespread continental species. Secondly, because of their restricted occurrence, even localized threats may affect all individuals of a species at once. Lastly, many island species have evolved in the absence of predators or competitors. Their naivety renders them vulnerable to the impact of introduced species, including humans. Land snails on islands are no exception, and they represent the animal group with the highest number of recorded extinctions worldwide. Although Lord Howe Island has maintained a fair proportion of its natural environment, it has not entirely escaped the menace of extinction. At least one land snail species ( Epiglypta howeinsulae ) and several subspecies (belonging to genera Placostylus and Gudeoconcha ) are considered to be extinct. A further three are highly likely to be extinct ( Melloconcha miranda , Deliciola charis and Pseudocharopa exquisita ) and at least five further species are threatened with extinction. These endangered or critically endangered species are the charopids Pseudocharopa ledgbirdi , P. whiteleggei , and Mystivagor mastersi , the helicarionid Gudeconcha sophiae magnifica , and the bothriembryontid Placostylus bivaricosus . Black Rats introduced to the island in 1918 are considered as the main threat to the survival of all these species. With rats removed from the island in 2019, a slow recovery of the endangered land snails will hopefully occur. However, at least two other conservation threats remain and could increase in significance. Over the last few years the climate on the island appears to have seen a shift to warmer and drier conditions, which has particularly impacted the critically endangered Oceanic Cloud Rainforests that are restricted to the top of Mount Gower. Several land snails appear to be confined to this ecological community and may be threatened with extinctions should this community disappear as a result of global warming. Introduced foreign pest species may pose another threat to native species either as predators or as competitors for limited ecological resources. In particular the European Garlic Snail ( Oxychilus alliarius ), which has been recorded on the island, may be of concern. This species has only recently been recognised as a potentially significant threat in Hawaii, where it preys on native species.