Life cycle variation and the genetic structure of nematode populations

Few data are available on population genetic structure in nematode species, and little of the available data allows direct comparison of the genetic s tructures of species having different life cycles. Here we use mtDNA sequen ce data to describe the genetic structure of a heterorhabditid nematode, an d compare results to published data on other nematode species. Heterorhabdi tis marelatus is a parasite of soil-dwelling insects. Its life cycle and lo cal ecology should result in small effective population sizes and restricte d gene how. As predicted, H. marelatus shows much lower mtDNA diversity wit hin populations and over the species as a whole, and has a much more strong ly subdivided population structure, than parasites of mobile vertebrate hos ts. From data such as these we can begin to generalize about the effects of life cycle variation on genetic structure in different nematode species.