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Ecology, 79(6), 1998, pp. 18471858 1998 by the Ecological Society of America
 

Summary: 1847
Ecology, 79(6), 1998, pp. 1847­1858
1998 by the Ecological Society of America
ONTOGENETIC REACTION NORMS OF PREDATOR-INDUCED DEFENSIVE
MORPHOLOGY IN DRAGONFLY LARVAE
GO¨ RAN ARNQVIST AND FRANK JOHANSSON1
Department of Animal Ecology, University of Umea°, S-901 87 Umea°, Sweden
Abstract. The study of phenotypic plasticity, one of the most important mechanisms
of phenotypic adaptation, is by tradition focused on differences in ontogenetically static
phenotypic expression in different environments. Ontogenetic reaction norms, in contrast,
describe how phenotypes unfold during growth in different environments. We studied the
ontogenetic reaction norms of the morphological shape of a series of defensive abdominal
spines in dragonfly larvae, both in the laboratory and in a number of natural populations.
In a laboratory rearing experiment, we demonstrated that these spines grew more solid and
elongated when waterborne environmental cues of fish predators were present: this is ev-
idence of phenotypic plasticity in defensive spine morphology. The ontogenetic reaction
norms of defensive spines were also found to differ in natural populations with and without
fish. A detailed analysis of the growth trajectories showed that this differentiation was
primarily due to ontogenetic acceleration in environments with fish, leading to relatively
exaggerated spine shape in these environments. However, while the ontogenetic trajectories

  

Source: Arnqvist, Göran - Department of Animal Ecology, Uppsala Universitet

 

Collections: Environmental Sciences and Ecology