Mitochondrial DNA diversity in nematodes.

The relatively small literature on mitochondrial DNA (mtDNA) diversity in nematode species is summarized here. Nematodes show a wide range of overall genetic diversities and population genetic structures. Species-wide levels of diversity correlate strongly with the breeding system and other life cycle features that control effective population size. Obligate outcrossers that parasitize mobile vertebrate hosts are the most diverse, species having hermaphroditic stages are less so, and species having asexual reproductive stages appear even less diverse. Nevertheless, these conclusions are preliminary because there exist so few data on DNA diversity in nematodes. What is needed are more comparative studies using similar sampling designs and the same DNA markers, including nuclear loci and further work with mtDNA.