Hi

Also food can be a rarefying factor. In a 'balanced' ecosystem there are
always more herbi- and/or omnivores than carnivores. So I think that
carnivorous molluscs like some Conidae species stand a greater chance of
being rare (low abundance in its range) than for example a Periwinkle
species :-).

By the way does someone know of a rare Periwinkle species (low abundance in
its range)?

greetinx, Erick