Geographic variation in lower pharyngeal jaw morphology in the Shiner Perch Cymatogaster aggregata (Embiotocidae, Teleostei)

Abstract

Correlations of feeding morphology with body morphology reflect ecological variation of a species and the geographic or ontogenetic scales over which it occurs. In this study, evidence was found for geographic variation in lower pharyngeal jaw (LPJ) morphology of Cymatogaster aggregata Gibbons (Embiotocidae, Teleostei) in the Pacific Northwest, U.S.A. Correlations of LPJ morphology with body morphology were more obvious in adulthood than the juvenile stage. Morphological patterns corresponded better with environmental variables and gut contents than geographic proximity, indicating that they were most likely caused by habitat differences. Qualitative common garden experiments indicated the nature and direction of plastic responses, and indicate a likely plastic origin to most naturally observed differences. Recognizing ecological patterns via morphology is an important first step in understanding how and when ecological mechanisms influence the functional role of an organism within its environment.