Towards a biogeography of free-living soil nematodes. I. Changing species richness, diversity and densities with changing latitude

The species richness, densities and biomass of free-living soil nematodes are often higher at high latitudes than at lower latitudes. Nematodes consequently dominate some high latitude invertebrate faunas. The diverse and abundant micro-organisms at high latitudes support many nematodes, although adaptability and lack of competitors also contribute to nematode importance. Nematodes contribute little to tropical soil invertebrate faunas because many specialized competitors are present. However, unlike at high latitudes, nematodes which feed on higher plants are relatively important in tropical faunas. Nematodes are most diverse and abundant in temperate regions, where they experience partial ecological release due to the absence of tropical competitors. Higher plant feeding nematodes are particularly important in temperature regions, where man's agricultural practices favour their persistence and dispersal. The Antarctic nematode fauna has fewer species and lower densities than that of the Arctic. This is because the Antarctic offers fewer opportunities for dispersal, and has a harsher climate, which limit the flora and fauna. Increasing altitude resembles increasing latitude in its effect on nematode distribution and abundance.