Conservation implications of mismatched diversity between mangrove plants and benthic mollusks

Understanding biodiversity patterns across multiple taxonomic groups is crucial for effective conservation planning to address the rapid global decline in biodiversity. While mangrove plant diversity has been extensively studied, the associated fauna, particularly benthic animals, have received insufficient attention. In this study, we compiled a dataset of mangrove benthic mollusks based on field surveys, including 27,610 individuals representing 160 species across 10 natural reserves. We also included the corresponding mangrove plant species lists from field surveys and species inventories for each reserve on tropical Hainan Island, China. We analyzed the relationship between mollusk diversity and mangrove plant species richness. Results show no consistent alignment between plant and mollusk diversity, with non-significant Spearman correlation coefficients (P > 0.1). Furthermore, five out of ten sites exhibit either below-average mollusk diversity with above-average plant diversity or below-average plant diversity with above-average mollusk diversity. This suggests that plant diversity is not a reliable surrogate for mollusk diversity, and vice versa. These mismatches complicate conservation planning, as protecting a single site cannot ensure multi-taxon biodiversity. We recommend that the design of protected areas and conservation assessments include multiple taxonomic groups. In mangrove ecosystems, monitoring plant diversity alone is insufficient, and other groups, such as the mollusks examined in this study, should also be considered.