The interspecific relationship between abundance and body size in central European land snail assemblages

Abstract

Summary The distributions of abundance and body size and the interspecific relationship between abundance and body size in Central European assemblages of terrestrial snails were analysed to investigate whether the characteristics of land snails, especially their limited active dispersal abilities, result in differences from the macroecological patterns mainly found in analyses of vertebrates. The distributions of crude density (number of specimens divided by the sum of the sampled areas) and ecological density (number of specimens divided by the sum of the areas sampled in the habitat types where a given species had been recorded) and of body size are approximately log-normal. Controlling for phylogenetic relationships there was a significant positive correlation between the number of habitat types occupied by a species and its crude and ecological density. The negative relationship between the two measures of abundance and body size found in the across-species analyses could not be confirmed in the phylogenetic contrasts analyses. The slopes of the body size–abundance relations are shallower than predicted by the energetic equivalence rule, even if only the upper bound slopes are considered and irrespective of the regression method used. This indicates that large snail species control a greater proportion of available resources than smaller species. Most of the macroecological patterns found in land snails are similar to those of other animal groups. An exception is the approximately log-normal distribution of log-transformed body sizes which may be a consequence of the better passive dispersal ability of smaller snails.