TROPHIC CONSEQUENCES OF DIFFERENTIAL PERFORMANCE - ONTOGENY OF ORAL JAW-CRUSHING PERFORMANCE IN THE SHEEPSHEAD, ARCHOSARGUS-PROBATOCEPHALUS(TELEOSTEI, SPARIDAE)

Studies in the held of ecomorphology aim to delineate the role of anat omy in determining an organism's ecological niche. Although an extensi ve literature exists correlating trophic morphology with biological ro le, surprisingly little research has investigated the causal relations hip between morphological variation and differential feeding performan ce. This study examines the possible role of oral jaw-crushing perform ance in moulding diet in an ontogenetic series of sheepshead, Archosar gus probatocephalus (Sparidae: Teleostei). By comparing potential nich e, as determined by anatomical predictions of force production, with r ealized niche, as determined by field studies investigating prey use i n the natural environment, we were able to assess to what degree maxim al capabilities affected resource use. Evidence strongly suggested tha t oral jaw-crushing force was an important determinant of diet in thes e fishes. All oral jaw elements, as well as force produced by the addu ctor mandibulae complex, scaled with positive allometry, which was con sistent with the increase in hard prey taken. There was a significant correlation between increased force production and increased durophago us habit. Lastly, the force used to feed in nature increased at the sa me rate as the predicted maximum force generated by the adductor mandi bulae complex. Studies such as this one speak directly to the relation ship between maximum functional potential and actual patterns of resou rce use.