The distribution of plant parasitic nematodes is largely a result of dispersal capabilities, human activities and historical biogeographic processes. Given high-resolution taxonomic approaches like DNA barcoding, we can more precisely evaluate hypotheses intended to explain observed patterns of nematode distributions. Some commonly evoked, but seldom tested patterns include: cosmopolitan distributions, centers of origin, latitudinal gradients, and areas of diversity and endemicity. We have been able to evaluate some of these patterns and their associated processes by phylogenetic and phylogeographic analyses using mtDNA COI sequences. Nematodes in the families Pratylenchidae, Meloidogynidae, and Heteroderidae which have enhanced dispersal capabilities due to their feeding behavior and association with major agronomic crops generally exhibit weak distribution patterns characterized by multiple long distance dispersal events. Nematodes in the family Criconematidae which typically have limited dispersal capabilities and relatively few associations with agronomic crops, exhibit strong distribution patterns in North America consistent with the recolonization of plant communities following the retreat of the Wisconsin Glacier 18,000 years ago. One surprising pattern emerging from an analysis of Criconematidae, is that of biome conservatism, wherein species tend to retain their ancestral ecology over millions of years and shifts between biomes are rare. A better understanding of this process may help predict future nematode distribution in a dramatically changing climate.