Molecular methods reveal controls on nematode community structure and unexpectedly high nematode diversity, in Svalbard high Arctic tundra

Nematodes are among the most abundant metazoans in soils, but their true diversity and distribution patterns remain poorly investigated, especially in polar environments. Here, we studied three high Arctic tundra sites at Kongsford, NW Svalbard (78 degrees 55'N) to understand: (1) Whether there is detectable small-scale habitat variation, (2) What the predictors of diversity and community variation are, and (3) Whether molecular methodology reveals greater diversity than morphological studies. DNA was extracted using the Baermann funnel method, and PCR amplified for the 18S rRNA gene, followed by 454-pyrosequencing. Our samples revealed no difference in nematode OTU alpha-diversity between different tundra habitats. Similarly, we found no correlation between nematode alpha-diversity in individual samples and soil properties or vegetation coverage. However, beta-diversity was lower in the highly vegetated tundra than in the other tundra. There was no evidence of distinct nematode communities between individual 1 m(2) quadrats of different vegetation cover and soil parameters. Overall, the community composition of highly vegetated tundra clustered separately from less vegetated tundra. The phylogenetic community assembly analysis indicated that the variation of nematode community was deterministic. This suggests that-despite the 'extreme' environment-nematodes in the high Arctic tundra are still to some extent habitat specialized. This study also revealed a much greater overall nematode diversity than has been previously detected in Svalbard. The nematode OTU diversity in our samples was considerably higher than the total species previously reported. This suggests the potential of DNA-based methods to rapidly reveal the true diversity of metazoans.