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At the end of the 19th century, the suggestion was made by several scientists, including J. M. Baldwin, that behavioral responses to environmental change could both rescue populations from extinction (Baldwin Effect) and influence the course of subsequent evolution. Here we provide the historical and theoretical background for this argument and offer evidence of the importance of these ideas for understanding how animals (and other organisms that exhibit behavior) will respond to the rapid environmental changes caused by human activity. We offer examples from long-term research on the evolution of behavioral and other phenotypes in the adaptive radiation of the threespine stickleback fish (Gasterosteus aculeatus), a radiation in which it is possible to infer ancestral patterns of behavioral plasticity relative to the post-glacial freshwater radiation in northwestern North America, and to use patterns of parallelism and contemporary evolution to understand adaptive causes of responses to environmental modification. Our work offers insights into the complexity of cognitive responses to environmental change, and into the importance of examining multiple aspects of the phenotype simultaneously, if we are to understand how behavioral shifts contribute to the persistence of populations and to subsequent evolution. We conclude by discussing the origins of apparent novelties induced by environmental shifts, and the importance of accounting for geographic variation within species if we are to accurately anticipate the effects of anthropogenic environmental modification on the persistence and evolution of animals. [ABSTRACT FROM AUTHOR]

Freshwater threespine stickleback fall along a benthic (bottom feeding)–limnetic (plankton feeding) continuum of ecotypes. Although trophic and courtship behaviour are well-described, the full reproductive cycle has not been characterized in the ecotypes. We provide detailed in situ descriptions of the reproductive cycle of males in one population of each ecotype, and a less detailed description in one oceanic population likely to represent the ancestral form that gave rise to the post-glacial freshwater radiation in southern British Columbia. All populations exhibited typical patterns including: pre-spawning nest building, fanning (which peaked in intensity just before hatching of embryos), and gluing (which was most common from nest building through the early parental phase). These elements of behaviour may be fixed by the physiological requirements of the fry. Males in the benthic and oceanic populations interacted frequently with groups and solitary non-neighbours, reflecting the abundance of bottom-feeding adults. Interactions with groups did not occur in limnetic populations and those with solitary non-neighbours were rare. Interactions were common with neighbours in all populations, but in the limnetic population they were conspicuous and ritualized, rather than the simple chases observed in the other populations. Males in the limnetic population also attended to the nest more, in some cases producing a 3-cm mound of sediment following the completion of spawning and often placing rushes around the pit-nest. The general pattern was one in which males in the cannibalistic benthic and oceanic populations appeared to be constrained in their interactions with neighbours and their attention to the nest by the need for vigilance and nest defense, while limnetic males attended more to nests and neighbours, possibly exhibiting the optimal pattern of nest-directed activities for the fry. [ABSTRACT FROM AUTHOR]

If an ancestral stem group repeatedly colonizes similar environments, developmental plasticity specific to that group should consistently give rise to similar phenotypes. Parallel selection on those similar phenotypes could lead to the repeated evolution of characteristic ecotypes, a property common to many adaptive radiations. A key prediction of this "flexible stem" model of adaptive radiation is that patterns of phenotypic divergence in derived groups should mirror patterns of developmental plasticity in their common ancestor. The threespine stickleback radiation provides an excellent opportunity to test this prediction because the marine form is representative of the ancestral stem group, which has repeatedly given rise to several characteristic ecotypes. We examined plasticity of several aspects of shape and trophic morphology in response to diets characteristic of either the derived benthic ecotype or the limnetic ecotype. When marine fish were reared on alternative diets, plasticity of head and mouth shape paralleled phenotypic divergence between the derived ecotypes, supporting the flexible stem model. Benthic and limnetic fish exhibited patterns of plasticity similar to those of the marine population; however, some differences in population means were present, as well as subtle differences in shape plasticity in the benthic population, indicating a role for genetic accommodation in this system. [ABSTRACT FROM AUTHOR]