Original Article

Heredity (2005) 94, 426–434. doi:10.1038/sj.hdy.6800623 Published online 26 January 2005 doi:6800623A/sj.bjp.0704832

Testing the hypothesis of recent population expansions in nematode parasites of human-associated hosts

D A Morrison1 and J Höglund1

1Department of Parasitology (SWEPAR), National Veterinary Institute and Swedish University of Agricultural Sciences, 751 89 Uppsala, Sweden

Correspondence: DA Morrison, Department of Parasitology (SWEPAR), National Veterinary Institute and Swedish University of Agricultural Sciences, 751 89 Uppsala, Sweden. E-mail: David.Morrison@vmm.slu.se

Received 25 February 2004; Accepted 18 October 2004; Published online 26 January 2005.

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Abstract

It has been predicted that parasites of human-associated organisms (eg humans, domestic pets, farm animals, agricultural and silvicultural plants) are more likely to show rapid recent population expansions than are parasites of other hosts. Here, we directly test the generality of this demographic prediction for species of parasitic nematodes that currently have mitochondrial sequence data available in the literature or the public-access genetic databases. Of the 23 host/parasite combinations analysed, there are seven human-associated parasite species with expanding populations and three without, and there are three non-human-associated parasite species with expanding populations and 10 without. This statistically significant pattern confirms the prediction. However, it is likely that the situation is more complicated than the simple hypothesis test suggests, and those species that do not fit the predicted general pattern provide interesting insights into other evolutionary processes that influence the historical population genetics of host–parasite relationships. These processes include the effects of postglacial migrations, evolutionary relationships and possibly life-history characteristics. Furthermore, the analysis highlights the limitations of this form of bioinformatic data-mining, in comparison to controlled experimental hypothesis tests.

Keywords:

demographic expansion, population growth, mitochondrial genes, nematoda, host–parasite relationships

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