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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]

At the onset of adaptive differentiation caused by colonization of new environments, patterns of ancestral plasticity can influence trait expression, and thus determine which phenotypes are exposed to selection. This hypothesis can be evaluated in the postglacial adaptive radiation of threespine stickleback, Gasterosteus aculeatus, in northwestern North America. The very large oceanic populations that gave rise to the freshwater radiation are unlikely to have changed significantly since colonization was initiated, so the pattern of plasticity in oceanic fish can be used to infer the ancestral pattern. We demonstrate that courtship behaviour in oceanic sticklebacks is plastic and suggest that its expression is mediated by large cannibalistic foraging groups that attack and consume young in nests defended by males. We then demonstrate that, under laboratory conditions, males from two benthic (bottom-feeding) populations, where group cannibalism is common, zigzag less than males from a limnetic (plankton-feeding) population in which such groups do not form. The difference in courtship behaviour of these ecotypes parallels that seen in the field and the pattern of plasticity observed in oceanic fish. Ecotypic differences were also retained in laboratory-reared fish from one limnetic and one benthic population. Biting was a more common component of courtship in the laboratory than in the field, and males from freshwater populations bit more than those from the oceanic population, a difference that disappeared in laboratory-reared benthic and limnetic males. Our results suggest that ancestral plasticity may have influenced the subsequent evolution of some elements of courtship behaviour in the stickleback radiation. [Copyright &y& Elsevier]

Abstract: Recent adaptive radiations offer special insight into the processes that generate biodiversity. The loss of unique members of such radiations undermines their collective evolutionary potential, as well as the ability of scientists to compare divergent populations, thereby devaluing the entire radiation as a system of study. To illustrate our case, we consider the adaptive radiation of the threespine stickleback fish (Gasterosteus aculeatus) in light of anthropogenic threats. Specifically, we consider the effects of stocking with rainbow trout, Onchorynchus mykiss, on populations of stickleback in lakes of two types in the Cook Inlet Region of Alaska, USA: (1) those in which salmonids are native and (2) those historically devoid of predatory fish. Many populations in this second class exhibit reduced pelvic armor that is, in part, a consequence of the historical absence of piscine predators that prey upon stickleback. Long-term trapping data from 77 lakes show that stocking in lakes where trout are not native is associated with large fluctuations in stickleback abundance, relative to lakes in which trout are native, or to lakes in which trout are neither native nor stocked. Pelvic-reduced populations appear to be at most risk from stocking. We discuss how these populations have responded to, and may yet respond to such threats, and how the information we have on these populations can be used to identify evolutionarily significant units (ESUs: ), and certainly, distinct populations segments (DPSs: ) deemed worthy of protection under Section 3(15) of the 1973 US Endangered Species Act as amended in 1978. Finally, we consider relevance of our results to the conservation of other recent adaptive radiations. [Copyright &y& Elsevier]

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]