Low Genetic Diversity in Wide-Spread Eurasian Liver Fluke <i>Opisthorchis felineus</i> Suggests Special Demographic History of This Trematode Species

<div><p></p><p><i>Opisthorchis felineus</i> or Siberian liver fluke is a trematode parasite (Opisthorchiidae) that infects the hepato-biliary system of humans and other mammals. Despite its public health significance, this wide-spread Eurasian species is one of the most poorly studied human liver flukes and nothing is known about its population genetic structure and demographic history. In this paper, we attempt to fill this gap for the first time and to explore the genetic diversity in <i>O. felineus</i> populations from Eastern Europe (Ukraine, European part of Russia), Northern Asia (Siberia) and Central Asia (Northern Kazakhstan). Analysis of marker DNA fragments from <i>O. felineus</i> mitochondrial <i>cytochrome c oxidase subunit 1</i> and <i>3</i> (<i>cox1, cox3</i>) and nuclear rDNA <i>internal transcribed spacer 1</i> (<i>ITS1</i>) sequences revealed that genetic diversity is very low across the large geographic range of this species. Microevolutionary processes in populations of trematodes may well be influenced by their peculiar biology. Nevertheless, we suggest that lack of population genetics structure observed in <i>O. felineus</i> can be primarily explained by the Pleistocene glacial events and subsequent sudden population growth from a very limited group of founders. Rapid range expansion of <i>O. felineus</i> through Asian and European territories after severe bottleneck points to a high dispersal potential of this trematode species.</p></div

Mismatch distribution curve for <i>O. felineus</i> haplotypes.

<p>Expected values under expanding population model and observed values are shown as solid green and dashed red lines, respectively (r – ruggedness index).</p

Diversity indices calculated from the nucleotide data sets for <i>cox1</i>, <i>cox3</i> and <i>ITS1</i>.

<p>Abbreviations are number of isolates examined (N), segregating sites (S), number of haplotypes (H), haplotype diversity (Hd) and nucleotide diversity (π).</p>*<p>- p<0.05.</p

The statistical parsimony networks of <i>cox1, ITS1</i> and <i>cox3</i> haplotypes.

<p>The sizes of haplotypes are proportional to the number of samples. Small black circles indicate un-sampled or extinct haplotypes.</p

Geographical localities where the specimens were collected.

<p>Lettered names of collection sites correspond to those in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0062453#pone-0062453-t001" target="_blank">Table 1</a>.</p

Neutrality indices calculated from the nucleotide datasets for <i>cox1</i>, <i>cox3</i> and <i>ITS1</i>.

*<p>- p<0.05.</p

Pairwise fixation indices (Fst values) between <i>O. felineus</i> populations calculated from the nucleotide datasets for c<i>ox1</i>/<i>cox3</i>/<i>ITS1</i>.

*<p>- p<0.05,</p>**<p>- 0.1>p>0.05.</p