Patterns in the distribution of Melanesian land Mollusca

Abstract

Melanesia is important in any discussion concerned with the distribution of terrestrial Mollusca in the Pacific region, as a zone exhibiting an intermingling of faunas derived from different geographical areas. Along the chain of islands constituting Melanesia these faunal elements exhibit changing patterns consistent with island hopping across water gaps. Yet the numbers of species of Mollusca on these islands show a positive correlation with the size of the individual islands (figure 19) and not, as might be expected, with the distance of particular taxonomic groups from centres of dispersal. Variations in this pattern can be attributed to differences in the isolation of islands, ecological diversity and the paucity of collecting in many areas. It should be realized that the distributional patterns recorded for any particular taxon must reflect the frequency and density of collecting and the inadequacies of the systematics of the group, besides biological attributes of the taxon and the island. The limitations should not distract, however, from attempts to analyse the available information, instead they must serve as a guide to the difficulties involved.