Ecomorphological patterns linking morphology and diet across three populations of pumpkinseed sunfish (<i>Lepomis</i><i> gibbosus</i>)

Abstract

Relationships between morphological traits and their ecological function frequently result in patterns that are consistently observed within taxa. Across fishes, the field of ecomorphology has identified a number of morphological traits linked to foraging tactic. Here we examined the links between morphology and diet in pumpkinseed sunfish (Lepomis gibbosus (L., 1758)) from three temperate freshwater lakes. We focused on morphological variation in pharyngeal jaw and gill raker structures, both involved with the processing of prey after capture, in relation to diet. Using stomach contents and stable isotope analysis, we established mean resource use estimates for both populations and individual fish. Among populations and individuals within lakes, we observed that pharyngeal jaw size and gill raker spacing increased with the consumption of littoral prey (e.g., hard-shelled snails) relative to pelagic prey (e.g., zooplankton), but the morphological changes were greater for the pharyngeal jaws. Overall, the relationships that we observed between morphology and foraging tactic were consistent with patterns observed in pumpkinseed and across other fishes. Individual-level diet variation associated with morphology may result in phenotypic diversity within populations that has multiple ecological and evolutionary implications for these populations.