Viewing two snail communities, the first community on the mainland and the second on Samui
Island in Surat Thani Province, 28 brackish-water
mollusk species were present on the mainland, and 15
species were evident on Samui Island, of which 11
snail species were common to both the mainland and
Samui Island (Table 5). Measurement of community
similarity, based on species presence, illustrated an
index of similarity of 0.51 (Table 5).