Meeting Abstract
Examining functional diversity and its evolutionary patterns requires quantification of a particular trait as a metric for disparity between species. Biomechanical models for force and displacement are a common tool in such studies, especially in feeding systems, and have elucidated countess insights into development, community composition, and ecology. Such models of feeding biomechanics primarily rely on metrics of jaw skeletal morphology such as the jaw adductor mechanical advantage. To accurately characterize the performance of a jaw system, however, both the skeletal leverage/linkage system and muscular actuation must be considered. Characteristics such as operating length (i.e. constraints of the force-length relationship), fiber angle, and ratio of muscle fiber strain to muscle-tendon-unit strain have at least an equivalent impact on organismal performance (arguably more) as skeletal morphology. Recent studies of ray-finned fishes have demonstrated that the force-length relationship of skeletal muscle constrains predator performance across prey sizes, fiber angle varies significantly across species, and the amount of muscle strain necessary for mouth opening can vary throughout ontogeny. Here, we demonstrate yet more functional diversity in fish feeding musculature by showing that: 1) the gape corresponding to optimal muscle force varies with feeding ecology in closely-related salmon species; 2) adductor muscle fiber architecture varies across salmon species; and 3) jaw skeletal morphology and Muscle fiber length evolve independently across sympatric sculpin species. Collectively, these data suggest the necessity of examining muscle morphology and physiology as axes of variation in functional diversity.
