Complex evolution of angelfish ecological diversity.

Tracings of video images showing different jaw protrusion patterns in (A) Centropyge [Xiphypops] (ventral), vs. (B) Centropyge [Centropyge], and all other taxa (forward). Upper jaw structures (front facing up; scale bar, 5 mm) showing cartilage discs (black arrows) in the pygmy angelfish clade (Figure 1) and difference in jaw profile between (C) C. [Xiphypops] and Genicanthus (flat) vs. (D) Pygoplites and all other taxa (curved). In the character matrix, relative gut length (mean ±S.D.) is coded as a discrete variable, and presence/absence of hindgut chambers and gizzards is shown. Trophic niche predictions are indicated on the far right. Note the complete correspondence as morphological character-states are optimised to the phylogeny under squared-change parsimony (Mesquite v. 2.5): H, herbivore; OG, gracile omnivore; OR, robust omnivore; P, planktivore, S, spongivore. Herbivory evolved independently in Pomacanthus [Euxiphipops] and C. [Xiphypops], which differ from congeners by having three times higher relative gut indices, presence of a hindgut chamber, and no gizzard. Large-bodied spongivores have short guts with a gizzard and a hindgut chamber. Robust omnivores share a medium-length gizzard-bearing gut but no hindgut. A short unspecialised gut unites the gracile omnivores. The planktivore Genicanthus resembles gracile omnivores but has the shortest gut in the family.