Interspecific interactions by allelopathy and predation in land snails.

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Interspecific inerference by growth reduction and predation was tested in experimental populations of Bradybaena similaris and Acusta despecta. As the results, B.similaris was clearly dominant in both predation and growth reduction. Second, the dominance of B.similaris was detected as its positive gains of increased growth and reduced cannibalism. The interspecific interactions by interference have been understood as negative effects against the recessive species. Thus, this result provides an example of interference interactions which causes both positive and negative effects for the dominant and recessive species, respectively. Densiyt effects on growth (intraspecific competition) were not statistically significant in A.despecta in the present conditions, whereas the growth of B.similaris was negatively correlated with density. Because of this contrast, the total density effect for B.similaris is lower when it lives with A.despecta than when all animals are B.similaris in the same total density. There were positive correlations between the individual inherent growth rate and the degree of growth interference A.despecta suffers. There was no detectable growth reduction in juveniles of slow growth, while the interference effect was significant in groups of fast growth. There was no detectable effect of composition and relative frequencies of the two species on the predation rate or growth interference.