Fig. 2: The larger phylogenetic signal for all traits is consistent with a more constrained dietary niche in the Caribbean.

A Relative phylogenetic signal for the two regions and the full dataset (gray) as quantified by Pagel’s Lambda (λ) using a bootstrapped analysis for each trait whereby the points represent the mean and error bars indicate SD of all bootstrapped iterations. In all cases, values significantly differ across regions and also between regions and the full dataset. Bi–ii Comparisons of standardized δ¹³C and δ¹⁵N (n = 499 and 829 for Caribbean and Polynesia, respectively for both δ¹³C and δ¹⁵N) distributions between two regions. “ks” indicates Kolmogorov–Smirnov tests for differences in the shape of the two distributions. “**” indicates statistical significance at α = 0.05. Percentages indicate the percent of iteratively sampled communities in which statistical significance was confirmed. Biii Standard ellipse area estimated from standardized isotopic values generated from iterative resampling (without replacement) of individuals from the two regions. “**” indicates that in all iteratively sampled communities ellipse areas were larger in Polynesia than the Caribbean—note the comparison of niche width is only for relative size, not location of the ellipse. The convex hull was also estimated for each sampled community and for all iteratively sampled communities the convex hull was larger in Polynesia than in the Caribbean.