Disappearing jewels: an urgent need for conservation of Fiji’s partulid tree snail fauna

Abstract

Where conservation status of island non-marine molluscs is known, snails tend to be one of the most threatened faunal groups. However, published information regarding island gastropod conservation status, diversity and endemism is frequently unavailable despite the importance of this information for the formulation of biodiversity action plans and conservation strategy. Fiji, for example, has a diverse native land snail fauna (>240 species) with an endemism level of ~80%, but only within the last few years has any information about any of these species been available to the national biodiversity reporting repository. For one lineage in particular, members of the tree snail family Partulidae, with four endemic Fiji Island species, the conservation status of the group has never been assessed. However, based on the alarming extinction rates documented in partulid snail species on other Pacific Islands, information about the occurrence and status of these taxa is urgently needed for Fiji’s biodiversity action plan. To redress this information void, we formulated the Fijian Partulid Tree Snail Project, consisting of five components: (1) raising awareness; (2) locating populations and monitoring population trends; (3) elucidating patterns of genetic diversity; (4) creating action partnerships; and (5) conducting disturbance gradient analyses. The overall goal was to characterise mechanisms leading to persistence of partulids in the face of increasing anthropogenic disturbance. In the initial stages of this project, existing information on Fiji’s partulids was collated and two small, remote islands in the Fiji archipelago were surveyed to investigate whether tree snails persisted there. Living populations of Partula lanceolata and empty shells of Partula leefei were found on Cicia Island in Lau, and on Rotuma Island in the Rotuma Group, respectively. DNA analyses confirm a sister relationship between the two Partula species in north-eastern Lau, P. lirata and P. lanceolata, with both sharing a sister relationship with a member of the same genus in Vanuatu – P. auraniana Hartman, 1888. Prioritisation and further sampling of additional islands, and residual native habitat on less accessible islands and islets, is needed to fully assess the conservation status of all four Fijian species via the IUCN Red List process. Moreover, the basic descriptive information and associated studies reported here will serve to raise awareness of Fiji’s endemic tree snails particularly in communities that had no prior knowledge of their special conservation status; and also at a wider national, regional and global level. Community awareness is particularly vital as the willing support of land owners in the relevant small island communities is critical to implementing any future conservation action plans.

Nonmarine Mollusks from Archaeological Sites on Mo‘orea, Society Islands, French Polynesia, with Descriptions of Four New Species of Recently Extinct Land Snails (Gastropoda: Pulmonata: Endodontidae)

“…It is now clear that both prehistoric and modern human activities have had a devastating effect on the native land snails inhabiting the high islands of tropical Polynesia (e.g., Christensen and Kirch 1986, Cowie 2001b, Bouchet and Abdou 2003, Lydeard et al 2004, Richling and Bouchet 2013Regnier, Achaz, et al 2015;Brodie et al 2016). This process began with initial human settlement and has only accelerated since the initiation of Western contact in the eighteenth century (Solem 1976(Solem , 1990Cowie 1992;.…”

Negative impacts of invasive predators used as biological control agents against the pest snail Lissachatina fulica: the snail Euglandina ‘rosea’ and the flatworm Platydemus manokwari

“…The impact of P. manokwari on the Fijian land snail fauna is presently unknown. In reviews of Fijian Placostylinae (Bothriembryontidae) and Partulidae (Barker et al 2016;Brodie et al 2016), P. manokwari is highlighted as an emerging threat to Fijian endemic land snail species.…”

“…During surveys in 2012 local adult people stated that the flatworm had been present at these locations for as long as they could remember. The status of Fiji's four species of endemic partulids (including one species, Partula leefei, endemic to Rotuma) was reviewed by Brodie et al (2016). Only empty shells of P. leefei were found during the 2012 survey, despite the species having been reported as numerous in 1938 (Gerlach 2016).…”