Fig. 4

Comparison of trophic level and littoral carbon in the diet in North American and Norwegian threespine sticklebacks. Mean (± SE) trophic position (Tpos) versus the proportion of littoral carbon in the diet (α) in twentyfive Norwegian freshwater stickleback populations (males and females pooled). The eight North American stickleback populations from Matthews et al. [20] are included for comparison of generalist to specialist populations. Here we have used the same ecological categorization of populations as in Matthews et al. [20], spanning limnetic, benthic and intermediate ecophenotypes. Two of the Norwegian populations are named for visual comparison of range in Tpos and α, namely the Einletvatn pond (limnetic ecophenotype) and Farstadvatn lake (benthic ecophenotype). In the top section, from left to right, are given head shape along the benthic-limnetic trophic axis (PC2 in Fig. 5) for Lake Einletvatn Pond, Lake Paxton-limnetic, Lake Paxton-benthic and Lake Farstadvatn. The depicted head shapes represents mean values from each of the populations