ABSTRACT
Plant nematodes reproduce amphimictically or autokonously, never asexually. In species that have males, unbalanced sex ratios are common and show a general trend toward an increased proportion of males when a population is subjected to environmental stress, even when sex is genetically determined. A number of distribution functions have been used to describe horizontal distribution of nematode populations and can help reduce the risk involved in basing crop damage estimates on nematode population estimates. The publication Distribution of Plant Parasitic Nematode Species in North America was an attempt to collate the known occurrences up to 1984. Taxonomic problems further confuse the problems in studying wide distributions of plant parasitic nematodes. Techniques applied in population ecology can be applied to communities; community changes can result from normal cyclic patterns, and competition or a density-dependent factors, environmental constraints, and many other events.
