In functional ecology, morphology is expected to reflect function, however, occasional decoupling of these two can be found. We did not find a relationship between feeding functional morphology and feeding modes of the American parrotfishes of the genera Scarus and Sparisoma. We explore some possible morpho-functional reasons for this phenomenon and reconsider the functional diversity within the scrapers. A phylogenetic tree including 50 species of parrotfishes, based on 12 genes, was reconstructed over which all analyses were performed. We found that although all Scarus species feed only by scraping, they are morpho-functionally more diverse compared to Sparisoma species, which have three different feeding modes (scraping, browsing and excavating) but appear to be morpho-functionally constrained. We quantified and compared the morpho-functional diversity within each genus using the disparity of the oral jaw feeding mechanics. An ecological convergence on scraping between all Scarus species and Sparisoma aurofrenatum was found. This result was supported by the ancestral feeding mode reconstruction and the absence of morpho-functional similarities between Scarus species and Sparisoma aurofrenatum. It is possible that different selective pressures or ecological conditions have shaped the differences both in the feeding ecology and the feeding morphology of these two genera. It is probable that key novel structures and muscular properties found in the jaw of Scarus species played an essential role in the morpho-functional diversification of this genus. Finally, there is the possibility that proposed feeding modes do not fully capture the complexity of their feeding ecology.

These files contain morphological quotients (values phylogenetical regressed against head length) of parrotfishes feeding traits. Raw morphological traits were obtained from photographs of the head of 15 species of parrotfishes of the New World. We also attached a file with all the corresponding feeding modes, maximum total length, and the phylogenetic tree we built to make all the analyses. Additionally, we have attached some R scripts we used to calculate the phylogenetical PCA and to calculate the morphological disparity.