Coexistence in Helminths of the Bank Vole Clethrionomys glareolus. I. Patterns of Co-Occurrence

We describe the patterns of co-occurrence in gastrointestinal helminths of the bank vole Clethrionomys glareolus at two localities in Finland, Pallasjarvi in western Lapland and Lammi in southern Finland. Four of 12 pairs of helminth species showed significant, but often inconsistent, positive co-occurrence patterns (presence - absence data). Similarly, the significant pairwise correlations in helminth abundance were rare (three of 10 pairs) and inconsistent. The rarity of significant overall associations among helminth species in the presence-absence data (two positive associations in seven data sets) and total absence in the density data support the idea of independent co-occurrence