Relationships between limestone physical parameters and land snail species diversity of the 12 limestone hills in Perak, Malaysia. Limestone hills size indicated by relative point size in the plot. A Relationship between species richness and number of unique species B Relationship between species richness and limestone hills size (km2) C Relationship between species richness and degree of isolation of the limestone hills D Relationship between number of unique species and limestone hills size (km2) E Relationship between number of unique species and degree of isolation of the limestone hills.