Biodiversity and conservation assessment of the non-marine mollusks of the Batanes Group of Islands, Philippines

Species in isolated small islands are susceptible to extinction, especially when major environmental changes occur. The non-marine mollusks of the Batanes Group of Islands (BGI) have not been extensively surveyed and monitored compared to vertebrates. We sought to determine the current non-marine mollusk diversity and assess the conservation status of the species found. A total of 92 man-hours of opportunistic sampling in nine sampling stations yielded 41 morphospecies (29 identified to species, 12 identified to genus), which comprised 14 operculated and 27 non-operculated snails. Of the 41 morphospecies, 25 were macro snails and 16 were micro snails (shell size ≤5mm). Species diversity tended to be high in limestone cliff sites and forests with karst outcrops, proving the importance of these habitats in maintaining overall biodiversity. The 29 species were assessed for conservation status using the Philippine National Red List evaluation guidelines for terrestrial invertebrates; nine fell within the category of Other Threatened Species (OTS) while 20 were categorized as Least Concern (LC). The OTS-classified species were macro snails that are collected for shell trade and/or consumed as food. Monitoring is recommended to ensure the maintenance of these populations in the future. Furthermore, the findings in this study undertones that limestone cliffs and karst outcrops should be protected from land conversion and quarrying as these habitats harbor a rich diversity of micro snails.