Meeting Abstract
Key innovations have periodically led to salient leaps in functional capacity, efficiency, and/or versatility. A series of modifications to the pharyngeal arches that resulted in a second functional set of jaws (i.e., the pharyngeal apparatus) are hypothesized to represent a major innovation that promoted diversification among cichlid fishes. Here, we test the degree of coevolution, or decoupling, among major functional aspects of pharyngognathy across a phylogeny of 97 Neotropical cichlids: pharyngeal bone shape, pharyngeal bone mass, and the mass of the musculature that operates the biting motion of the pharyngeal jaws. The masses of the lower pharyngeal jaw (LPJ) and muscular sling (MS) were correlated. In contrast, LPJ shape was not correlated with the masses of the LPJ or the MS; however, LPJ shape was correlated with body shape. LPJ and MS masses were variably constrained depending on LPJ shape. For example, species with narrowly-spaced LPJ lateral processes exhibited exclusively atrophied LPJ and MS masses. In contrast, species with widely-spaced LPJ lateral processes exhibited an array of LPJ and MS masses. The mass of pharyngeal bones and musculature are likely coevolved in association with the mechanistic generation of crushing force and subsequent tolerance of force-induced stress, whereas the shape of pharyngeal bones may be partly constrained by body shape. Modifications of LPJ size, shape, and associated musculature in concert is associated with the evolution of an array of trophic functions.
