Linking shell collections to conservation: Understanding the biodiversity patterns and distribution of marine mollusks in the Philippines

Abstract

Marine mollusks are among the most diverse and ecologically important groups in coastal ecosystems, yet patterns of diversity and distribution among islands remain poorly understood. In particular, species distribution and overlap between coastal localities in the Philippines remain unexplored, despite the archipelagic country being recognised for its exceptional biodiversity. This study uses a shell collection as an unconventional and non-invasive approach to documenting mollusk diversity, offering insights into rare and uncommon species often overlooked in conventional surveys and live sampling methods, through a comparative analysis of three islands: Ormoc, Leyte; Punta Engaño, Cebu; and Nocnocan, Bohol. Results reveal distinct biodiversity and low species overlap across the sites, with estimates of more than 60, 70, and 30 identified species, respectively, highlighting the differences among island communities. The one-way ANOVA showed a significant difference in diversity among sites (F=0.471, p<0.05). Nocnocan exhibits the lowest species richness and abundance, but demonstrates high evenness and a balanced species distribution, suggesting a stable yet constrained community dynamic, potentially due to its smaller size, isolation, and status as a tourist area. Ormoc and Punta Engaño displayed significantly higher species richness and abundance with Punta Engaño recording the highest biodiversity metrics. This pattern shows how island attributes may influence species diversity, highlighting the necessity for location-specific management approaches. While shell collections can provide useful insights, it is important to acknowledge that selective collection may influence results. Therefore, the value of shell collections may be used as a complementary tool, and the method can be further enhanced when interpreted alongside data from field sampling techniques, offering a more robust approach to documenting species and balancing the accessibility and historical value of collections with the ecological accuracy of direct sampling.