Phenotypic plasticity can influence evolutionary change in a lineage, ranging from facilitation of population persistence in a novel environment to directing the patterns of evolutionary change. As the specific nature of plasticity can impact evolutionary consequences, it is essential to consider how plasticity is manifested if we are to understand the contribution of plasticity to phenotypic evolution. Most morphological traits are developmentally plastic, irreversible, and generally considered to be costly, at least when the resultant phenotype is mis-matched to the environment. At the other extreme, behavioral phenotypes are typically activational (modifiable on very short time scales), and not immediately costly as they are produced by constitutive neural networks. Although patterns of morphological and behavioral plasticity are often compared, patterns of plasticity of life history phenotypes are rarely considered. Here we review patterns of plasticity in these trait categories within and among populations, comprising the adaptive radiation of the threespine stickleback fish Gasterosteus aculeatus. We immediately found it necessary to consider the possibility of iterated development, the concept that behavioral and life history trajectories can be repeatedly reset on activational (usually behavior) or developmental (usually life history) time frames, offering fine tuning of the response to environmental context. Morphology in stickleback is primarily reset only in that developmental trajectories can be altered as environments change over the course of development. As anticipated, the boundaries between the trait categories are not clear and are likely to be linked by shared, underlying physiological and genetic systems.

Instances of aggressive chase over a 5-mo period were investigated in captive killer whales (Orcinus orca). Such episodes were found to be quite rare, occurring only eight times in 1,872 h of observation. A consistent vocal pattern was found to be associated with agonistic episodes that differed markedly from the pattern recorded during non-aggressive, time-matched control periods. In general, vocalizations associated with aggressive chase were characterized by amplitude and frequency modulated pulses of approximately 190 ms in duration. In addition, three specific call types were found to occur only during chase events. As a whole, these particular call types and associated features are offered as an acoustic signature of agonism in the killer whale. It is hoped that these sounds might aid researchers in interpreting heretofore enigmatic killer whale vocalizations recorded from wild populations.

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