Ecological shifts underlie parallels between ontogenetic and evolutionary allometries in parrotfishes

During ontogeny, animals often undergo significant shape and size changes, coinciding with ecological shifts. This is evident in parrotfishes (Eupercaria: Labridae), which experience notable ecological shifts during development, transitioning from carnivorous diets as larvae and juveniles to herbivorous and omnivorous diets as adults, using robust beaks and skulls for feeding on coral skeletons and other hard substrates. These ontogenetic shifts mirror their evolutionary history, as parrotfishes are known to have evolved from carnivorous wrasse ancestors. Parallel shifts at ontogenetic and phylogenetic levels may have resulted in similar evolutionary and ontogenetic allometric trajectories within parrotfishes. To test this hypothesis, using micro-CT scanning and 3D geometric morphometrics, we analyze the effects of size on the skull shape of the striped parrotfish Scarus iseri and compare its ontogenetic allometry to the evolutionary allometries of 57 parrotfishes and 162 non-parrotfish..., To investigate growth allometry, we examined the ontogenetic series of S. iseri, encompassing 54 individuals with a total length ranging from 1.75 to 33.5 cm. 
For skull shape comparison analyses among S. iseri, other parrotfishes, and non-parrotfishes wrasses, our sample of adults comprises 336 individuals (160 adult parrotfishes and 176 adult non-parrotfish wrasses) from 217 labrid fishes (Table S1). From this dataset, we compared the evolutionary allometry of Scarines reef clade (57 species) to ontogenetic allometry of S. iseri. The ontogenetic series of S. iseri was obtained through sampling carried out in Belize in 2023 (IACUC protocols: UT Austin/AUP-2021-00064 and SERC/10-15-15-SJB; Collection permits: BF000005-16 and BF0042-22) with additional individuals from the Field Museum of Natural History (FMNH). The remaining species were obtained through several museums (Table S1).
We assessed the three-dimensional skull shape of each labrid species through micro-computed tomography (μC..., , # Ecological shifts underlie parallels between ontogenetic and evolutionary allometries in the striped parrotfish

Continued methods

**(a)   Ontogenetic allometry of *Scarus iseri***

To analyze the shape variation of entire skull and individual bones of *S. iseri* across development, we applied Principal Component Analysis (PCA) using *gm.prcomp* function in *geomorph* package (Adams et al., 2022).

To estimate coefficients of ontogenetic allometry and test the effects of size on skull and bone shapes (superimposed coords), we used Analysis of Variance, fitting a model with one main effect, the factor “Size”, measured as ln-transformed CS (LCS). The ANOVA was performed using the *procD.lm* function in *geomorph* (Collyer and Adams, 2018; 2021). To better visualize these relationships, we predicted individual shapes using group-specific regression models, and the resulting shapes for all samples were plotted using a PCA. We plotted PC1 scores against size. Allometric axes were then plo...