Morphological plasticity of native and non-native pumpkinseed sunfish in response to habitat type

Background: Aquatic environments contain discrete habitats that vary in structural com-plexity and resource availability. Non-indigenous organisms that exhibit a high degree of phenotypic plasticity may be more successful at foraging and navigating, in and around the novel environments. Goal: To investigate differences in morphological plasticity in young-of-year fish from native Canadian and non-native Iberian populations. Organism: Pumpkinseed sunfish (Lepomis gibbosus). Methods: Fish were reared for 80 days in enclosures that restricted individuals to either the littoral or pelagic zone of an artificial pond, while still permitting the passage of prey. Inter- and intra-population differences were tested using analysis of covariance and discriminant function analysis, while differences in plasticity were tested through a multivariate analysis of variance of discriminant function scores. Results: Regardless of geographic origin, fish held under pelagic conditions exhibited sig-nificantly wider caudal fin bases, and longer dorsal and ventral caudal peduncle lengths. All populations developed longer gill rakers and shorter and narrower jaw structures when held under pelagic conditions. Iberian populations exhibited less phenotypic plasticity than native Canadian populations. All pumpkinseed populations held under pelagic conditions appear to exhibit similar morphological changes geared towards enhancing their ability to swim and forage in open-water habitat