Morphospecies relative abundance by the number of sampling sites at which they were present. Point markers represent the 143 morphospecies coded according the three rarity categories: ‘dominant’ (circle), ‘common’ (triangles) and ‘rare’ (diamonds). Morphospecies classified as ‘dominant’ occurred at a higher number of sampling sites than ‘common’ morphospecies. ‘Common’ morphospecies occurred at a higher number of sampling sites than ‘rare’ morphospecies (P < 0.001).