SHELL SIZE AND POPULATION-DENSITY IN LARGE HELICID LAND SNAILS

(1) Negative associations between body size and population density are well known in diverse organisms, including land snails. (2) Much work on this phenomenon has been restricted to single-species considerations, such as the relationship with population regulation. (3) The question arises of which components of density (if any) body size responds to in mixed-species colonies. This is related to the question of how commonly interspecific competition occurs in nature. (4) Our results, for a group of four species of helicid land snails, show that while negative size-density associations are indeed found in single-species colonies, mixed colonies appear not to exhibit such associations, despite the increased number of comparisons that can be made and hence the increased chance of detecting them. (5) A possible explanation for this unexpected contrast between single and mixed colonies is discussed.