Authors

Discussion

We have been investigating the population genetics of Strongyloides ratti, a nematode that infects brown rats (Rattus norvegicus). Population genetic analysis can reveal a species’ population biology, and can be used to predict population-level responses to selection pressures. Nevertheless, very little is known about the population genetics of parasitic nematodes, especially those that infect wild animals

We have sequenced the whole genomes of individual S. ratti, sampled non-destructively from three wild rat populations. So far, results show strong genetic differentiation among S. ratti sampling sites. We detect a low level of gene flow among parasite populations, likely mediated by occasional long-range dispersal of rat hosts. We have serendipitously detected evidence of mitochondrial heteroplasmy in these parasite populations.

There is an uneven distribution of polymorphic sites within the S. ratti genome, possibly reflecting the action of selection. Loci putatively associated with the parasitic lifestyle have been detected in S. ratti. It will be interesting to see whether these genes share concerted patterns of selection, which could reflect ongoing adaptation of parasitic traits.

This work is revealing how genetic variation is distributed in S. ratti at three levels - within individual genomes, within populations, and among sampling sites.