Did Captain Beechey see a living Mandarina luhuana, an extinct land snail species?

Abstract

ABSTRACT Knowledge about prehuman biotas and the impact of early human contact, particularly on land snails inhabiting oceanic islands, is still poor. One specific example of interest is Mandarina luhuana, which was first collected from the Chichijima Islands of the Ogasawara Archipelago in 1827 during Captain Frederick William Beechey's expedition. The initial description of M. luhuana included an image of a shell with dark brown pigmentation, which contrasts with current understanding, with all known specimens being considered to lack dark colouration. Traditionally, it is believed that M. luhuana represents a fossil species that became extinct on the island before human arrival. However, I propose that the specimen collected for the original description was either recently dead or still alive at the time of collection. Furthermore, I hypothesize that M. luhuana faced extinction after human arrival on Ogasawara, which began during the 17th century. To test this hypothesis, I used accelerator mass spectrometry dating to determine the extinction dates of subfossil samples of M. luhuana. The results of this study suggest that M. luhuana became extinct after the 17th century, with the species having possibly survived until the early 19th century. It is likely that the extinction of M. luhuana occurred shortly after human arrival in the islands. These findings underscore the need for further research to understand the impact of human arrival on island ecosystems and to uncover the original diversity of land snail faunas on islands.