Organisms are composed of hierarchically arranged component parts that must work together to successfully achieve whole organism functions. In addition to integration among individual parts, some ecological demands require functional systems to work together in a type of inter-system performance integration. While performance can be measured by the ability to successfully accomplish ecologically relevant tasks, integration across performance traits can provide a deeper understanding of how these traits allow an organism to survive. The ability to move and the ability to consume food are essential to life, but during prey capture these two functions are typically integrated. Suction-feeding fishes have been used as a model of these interactions, but it is unclear how other ecologically relevant scenarios might reduce or change integration. To stimulate further research into these ideas, we highlight three contexts with the potential to result in changes in integration and underlying performance traits: (1) behavioral flexibility in aquatic feeding modes for capturing alternative prey types, (2) changes in the physical demands imposed by prey capture across environments, and (3) secondary adaptation for suction prey capture behaviors. These examples provide a broad scope of potential drivers of integration that are relevant to selection pressures experienced across vertebrate evolution. To demonstrate how these ideas can be applied and stimulate hypotheses, we provide observations from preliminary analyses of locally adapted populations of Trinidadian guppies (Poecilia reticulata) capturing prey using suction and biting feeding strategies and an Atlantic mudskipper (Periophthalmus barbarus) capturing prey above and below water. We also include a re-analysis of published data from two species of secondarily aquatic cetaceans, beluga whales (Delphinapterus leucas) and Pacific white-sided dolphins (Lagenorhynchus obliquidens), to examine the potential for secondary adaptation to affect integration in suction prey capture behaviors. Each of these examples support the broad importance of integration between locomotor and feeding performance but outline new ways that these relationships can be important when suction demands are reduced or altered. Future work in these areas will yield promising insights into vertebrate evolution and we hope to encourage further discussion on possible avenues of research on functional integration during prey capture.

In fishes, damage to important morphological structures such as fins through natural damage and anthropogenic factors can have cascading effects on prey capture performance and individual fitness. Bluegill sunfish (Lepomis macrochirus) are a common freshwater species in North America, are a model organism for performance studies, and often experience natural injuries. We opportunistically sampled two populations of fish in the lab to generate a hypothesis for the effect of sub-lethal fin damage resulting from capture technique on kinematic performance during prey capture in bluegill. We found no statistical differences in mean prey capture kinematics or predator accuracy, but damaged fish used more variable kinematics and more readily struck at non-prey items. We suggest that a reduction in stability and individual consistency occurs as a result of fin damage. This difference could have consequences for higher order ecological interactions such as competitive ability, despite a lack of apparent performance cost at the individual level, and deserves consideration in future studies of prey capture performance in fish.

Performance, the ability to complete an ecologically relevant task, serves as a link between underlying morphology and the maximum functional capacity and fitness of an individual. Performance can vary within species due to environmental context and the trait of interest, but this is less understood compared with variation across species. Trinidadian guppy (Poecilia reticulata) populations are separated by waterfall barriers that result in repeated selection for predator avoidance in high predation environments and resource competition in low predation environments. An array of locally adapted traits results from these shifts, however, the role of these local adaptations in prey capture performance traits remains unclear. We examined biting kinematics in replicate populations of adult female guppies collected from natural high and low predation habitats. We expected that competition in low predation populations would drive performance differences compared with fish from high predation populations. Using high-speed videos of fish feeding on an agar substrate, we did not find support for differences in jaw or approach kinematics between populations, suggesting a lack of local adaptation in our sample. To gain further insight, we examined four representative, whole-body morphometric traits previously shown to be divergent in guppies. Again, differences were not discovered in our sample, which may indicate limitations in the use of shape traits. We suggest that female guppies are kinematic generalists and that selection on prey capture may act on traits other than performance, such as feeding behaviors (e.g., consumption rates, kinematic integration, and prey preference).