Figure 1.
Distribution of three cryptic Gammarus fossarum species (types A, B and C) in Europe.
The Rhine drainage, which contains the contact zone between type A and type B, is shaded in grey. The small map on the top right indicates the position of the study area within Europe. The large map contains data from six previous publications (see text) and the present study. The method used for species identification is indicated (square = allozyme analysis; circle = sequencing), as the distinction between type B and C is not possible based on allozymes. For some sites, arrows indicate the flow direction of the sampled stream. The smaller map contains only the Swiss samples collected for this study and shows the exact species compositions of the samples in pie diagrams. Pie diagram size corresponds to sample size (n between 2 and 57 per population; total n = 1337). To prevent overlap of the pie diagrams, some positions are slightly shifted. The exact positions are shown in the large map.