Beaks promote rapid morphological diversification along distinct evolutionary trajectories in labrid fishes (Eupercaria: Labridae)

The upper and lower jaws of some wrasses (Eupercaria: Labridae) possess teeth that have been coalesced into a strong durable beak that they use to graze on hard coral skeletons, hard-shelled prey, and algae, allowing many of these species to function as important ecosystem engineers in their respective marine habitats. While the ecological impact of the beak is well-understood, questions remain about its evolutionary history and the effects of this innovation on the downstream patterns of morphological evolution.  Here we analyze 3D cranial shape data in a phylogenetic comparative framework and use paleoclimate modeling to reconstruct the evolution of the labrid beak across 205 species. We find that wrasses evolved beaks three times independently, once within odacines, and twice within parrotfishes in the Pacific and Atlantic Oceans. We find an increase in the rate of shape evolution in the Scarus+Chlorurus+Hipposcarus (SCH) clade of parrotfishes likely driven by the evolution of the in..., Shape Analyses
For the analysis of skull shapes, we used three-dimensional geometric morphometrics to quantify shape variation and diversity among our labrid dataset. We digitized the left side of each specimen with 79 landmarks and 118 semi-landmarks (Supplementary Table 1; Supplementary Figure 4) following the approach described in Larouche et al. (2022). Landmarks encompassed the skull, jaws, hyoid region, and pharyngeal jaws. The teleost fish skull exhibits immense biomechanical complexity, with highly kinetic, articulating elements (Westneat 2004; Hulsey et al. 2005). This kinesis poses a challenge to studies of shape change across the skull because preservational artifacts related to the relative positions of these individual elements can strongly bias any downstream analyses (Vidal‐García et al. 2018; Evans et al. 2019b). To account for this rotation and translation of mobile elements, we performed a local superimposition to standardize the position of the different skull element..., Analyses were run in R version 4.1.3 and BayesTraits Versions 3 and 4.