Trophic consequences of differential performance: ontogeny of oral jaw‐crushing performance in the sheepshead, Archosargus probatocephalus (Teleostei, Sparidae)

Abstract

Studies in the field of ecomorphology aim to delineate the role of anatomy in determining an organism's ecological niche. Although an extensive literature exists correlating trophic morphology with biological role, surprisingly little research has investigated the causal relationship between morphological variation and differential feeding performance. This study examines the possible role of oral jaw‐crushing performance in moulding diet in an ontogenetic series of sheepshead, Archosargus probatocephalus (Sparidae: Teleostei). By comparing potential niche, as determined by anatomical predictions of force production, with realized niche, as determined by field studies investigating prey use in the natural environment, we were able to assess to what degree maximal capabilities affected resource use. Evidence strongly suggested that oral jaw‐crushing force was an important determinant of diet in these fishes. All oral jaw elements, as well as force produced by the adductor mandibulae complex, scaled with positive allometry, which was consistent with the increase in hard prey taken. There was a significant correlation between increased force production and increased durophagous habit. Lastly, the force used to feed in nature increased at the same rate as the predicted maximum force generated by the adductor mandibulae complex. Studies such as this one speak directly to the relationship between maximum functional potential and actual patterns of resource use.