Fig. 1.

Community composition and diversity of amphipods in 13 tributary streams of Lake Constance (light blue) in 2012 (a) and 2013 (b). Local amphipod community composition is given with pie-charts for each site sampled, starting at the stream outlet (lake site) towards increasing upstream distance (0, 50, 100, 500, 1000 and 5000 m sites respectively, arranged from North to South). Pie-charts give the relative proportion of amphipod species for each site. Gammarus roeseli and Dikerogammarus villosus are non-native species, while the three other species are natives. For clarity, position and river-line of the 13 tributary streams are slightly schematised and shifted