Fig. 3. Changes in nitrogen isotope ratio (¹⁵N; ) in two tissues of Leptonycteris curasoae (A,C) and Glossophaga soricina (B,D) after the diet was changed at day one to plant products with a nitrogen isotope ratio that was more enriched in ¹⁵N by 9 ¹⁵N than the initial diet; mean values (± 1 S.D.) for blood are shown in A and B (open circles) and those for wing membrane in C and D (filled circles). Exponential regression functions were fitted to the data sets (solid line; see equations in the corresponding graphs). Broken lines give the expected regression lines calculated with the corresponding regression coefficients derived from the carbon isotope data set (Voigt et al., 2003b).