Malacologists Investigate Pacific Island Snail Diversity in Cook Islands Expedition

Researchers Dr. Isabel Hyman and Dr. Frank Köhler from the Australian Museum Research Institute conducted a scientific expedition to Rarotonga in the Cook Islands as part of a broader Pacific study. The project, funded by the Australia and Pacific Science Foundation with additional private support, aims to trace the evolutionary origins of land snail groups found on Australia's Lord Howe Island and Norfolk Island. These islands host over 120 endemic snail species across 11 families, but some groups like Microcystidae (glass snails) lack clear relatives in nearby regions. The team collaborated with Gerald McCormack, founding Director of the Cook Islands Natural Heritage Trust, who provided extensive local knowledge and access to the Cook Islands Biodiversity and Ethnobiology Database containing 4,500 species records. During their fieldwork, the researchers surveyed diverse habitats including coastal areas, lush interiors, and cloud forest peaks like Te Ko'u (588 m) and Te Manga (658 m). They documented 37 land snail species, including several microcystids of particular interest. The expedition confirmed the presence of four microcystid genera on Rarotonga: Lamprocystis, Diastole, Liardetia, and introduced Kororia. While they found previously recorded species like Liardetia samoensis and Diastole conula, they also discovered an undescribed Diastole species and encountered lower than expected diversity in some groups, raising questions about seasonal patterns or population declines. The introduced Kororia palaensis proved to be the most common glass snail. Preliminary analysis suggests Diastole may be the closest relative to Australian island taxa, though definitive conclusions await further Pacific sampling. The researchers plan future surveys to monitor glass snail populations and continue their investigation across the Pacific region.