Analysis of ecological niche breadth and comparison of habitat strategies of Korean freshwater mollusks under environmental gradients
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This study quantitatively analyzed the ecological niche breadth (ENB) of 27 freshwater mollusk species (11,406 occurrence records) in Korea based on macro environmental gradients, including climate, topography, and land cover. We combined Levins’ index values (B: niche breadth, BA: equitability) with optimum-tolerance analysis (optimum value and tolerance range, t95-t05) to determine species-specific habitat strategies and environmental responses. The analysis revealed a distinct dichotomy in the habitat strategies of Korean freshwater mollusks, separating cold-water, low disturbance types in upstream areas from warm-water, disturbance-tolerant types in downstream areas, mainly structured by thermal and land-cover gradients. Species, such as Semisulcospira libertina, Radix auricularia, and the alien species Physa acuta, were identified as generalists, showing high B values but low BA values, suggesting that they are capable of inhabiting diverse environments but concentrate their presence in certain environmental conditions. Conversely, Koreoleptoxis nodifila and Clithon retropictum were classified as specialists with low B values and intermediate to high BA values, indicating stable and equitable distribution within restricted environmental limits. Urbanization appeared to be an influential limiting factor, showing low BA values for most species, whereas agricultural areas showed higher BA values, suggesting a comparatively broader habitat possibility. Notably, K. nodifila, a critically endangered and endemic species, showed optimal habitat conditions of low temperature (10.65°C), low urbanization (4.82%), and high forest cover (57.34%), confirming its status as a cold-water indicator species adapted to forested upstream systems. The study findings provide a quantitative framework to assess the environmental tolerance, vulnerability, and conservation priorities of Korean freshwater mollusks.
Abstract
This study quantitatively analyzed the ecological niche breadth (ENB) of 27 freshwater mollusk species (11,406 occurrence records) in Korea based on macro environmental gradients, including climate, topography, and land cover. We combined Levins’ index values (B: niche breadth, BA: equitability) with optimum-tolerance analysis (optimum value and tolerance range, t95-t05) to determine species-specific habitat strategies and environmental responses. The analysis revealed a distinct dichotomy in the habitat strategies of Korean freshwater mollusks, separating cold-water, low disturbance types in upstream areas from warm-water, disturbance-tolerant types in downstream areas, mainly structured by thermal and land-cover gradients. Species, such as Semisulcospira libertina, Radix auricularia, and the alien species Physa acuta, were identified as generalists, showing high B values but low BA values, suggesting that they are capable of inhabiting diverse environments but concentrate their presence in certain environmental conditions. Conversely, Koreoleptoxis nodifila and Clithon retropictum were classified as specialists with low B values and intermediate to high BA values, indicating stable and equitable distribution within restricted environmental limits. Urbanization appeared to be an influential limiting factor, showing low BA values for most species, whereas agricultural areas showed higher BA values, suggesting a comparatively broader habitat possibility. Notably, K. nodifila, a critically endangered and endemic species, showed optimal habitat conditions of low temperature (10.65°C), low urbanization (4.82%), and high forest cover (57.34%), confirming its status as a cold-water indicator species adapted to forested upstream systems. The study findings provide a quantitative framework to assess the environmental tolerance, vulnerability, and conservation priorities of Korean freshwater mollusks.