Latitudinal trends in Glu and Phe δ¹⁵N values compared with bulk δ¹⁵N.

<p>Bold solid line indicates regression for bulk δ¹⁵N values for all sites sampled (as in Fig. 1), thin solid lines indicate linear regressions for Glu (open circles) and Phe (filled circles) (δ¹⁵N_Glu = −0.270x+24.211, δ¹⁵N_Bulk = −0.313x+21.527, and δ¹⁵N_Phe = −0.329x+19.927). ANCOVA analysis indicates that all three share a common slope within error (effects test, <i>P</i><0.0050). Error bars for Glu and Phe indicate analytical standard deviation for CSI-AA performed on a composite sample for all individual mussels from each site (<i>see methods</i>).