Density and environmental effects on shell size in some sand dune snail populations

Abstract

Populations ol three species of land snail, Helicella itala. Candidula intersecta and Cochlicella acuta are studied on sand dunes on Coll in the Inner Hebrides. Population density and mean shell size were estimated on 18 sample sites. The sites were ranked for six environmental factors. Environmental factors which are related to the dune vegetational succession account for much of the variation in the densities of C. intersecta and C. acuta. The density of H. itala, however, shows no strong association with these factors. Both snail density and shell size are reactively independent of total soil calcium levels. For each of the three species, mean shell size is negatively associated with population density; the environmental factors account for little of the variation in shell size. Four possible mechanisms are suggested to account for the variation of shell size with density. It is argued that a direct influence of density on shell size, possibly mediated by mucus conditioning of the environment is the most probable mechanism. There is some evidence to suggest an inter‐specific effect whereby C. intersecta density affects H. itala shell size.

Fecundity ofCochlicella acuta(Müller) (Mollusca: Helicidae) in laboratory cultures

“…There was no difference in the timing of oviposition by small and large adult snails. Crowding has also been shown to reduce the activity of some helicid snails (Cameron and Carter, 1979), but Tattersfield (1981) has suggested that the activity of C. acuta is not reduced by increased density. Density effects may be relatively unimportant in the ecology of C. acuta, if food is not limiting.…”

Clinal variation and natural selection in the land snail Pleurodonte lucerna in western St. Ann Parish, Jamaica

“…Adult size has been shown to be negatively correlated with population density in several European helicids. The relationship has been shown in field surveys of Cepaea nemoralis (Cook & O' Donald, 1971; Williamson et al , 1976;Oosterhoff, 1977) and three other helicid species (Tattersfield , 1981).…”

Geomorphologic and palaeoenvironmental development of holocene perched coastal dune systems in brittany, france

“…The Mollusca recovered from untreated sediment are given as Table 3. The basal sample (0.95-1.1 m) consists almost exclusively of Cochlicella acuta, a species typical of dunes and coastal grasslands (Kerney and Cameron 1979) and often associated with mobile or semi-fixed surfaces on dunes (Evans 1972;Tattersfield 1981). The lack of other species would also suggest a low-diversity environment, and a bare sand surface seems likely.…”