Distribution of the triclad Polycelis felina in Aezkoa mountains : effect of streams biotic features

The study of freshwater invertebrates composing macrobenthos communities of stream habitats can be of great importance for both ecological and conservational purposes. In this paper we analyse the distribution of the triclad Polycelis fauna in western Pyrenees along the Aezkoa Mountains where forests and pastures prevail. We found a relatively wide distribution of the species that was affected mainly by stream biotic characteristics, in particular by fish occurrence and gammarid abundance. These factors in a poorly urbanised area can reflect the importance of the well-structured community for the presence of P felina and its role as a bioindicator.