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Phenotypic plasticity is the capacity for an individual genotype to produce different phenotypes in response to environmental variation (1). Most traits are plastic, but the degree to which plasticity is adaptive or non-adaptive depends on whether environmentally induced phenotypes are closer or further away from the local optimum (2-4). Existing theories make conflicting predictions about whether plasticity constrains or facilitates adaptive evolution (4-12). Debate persists because few empirical studies have tested the relationship between initial plasticity and subsequent adaptive evolution in natural populations. Here we show that the direction of plasticity in gene expression is generally opposite to the direction of adaptive evolution. We experimentally transplanted Trinidadian guppies (Poecilia reticulata) adapted to living with cichlid predators to cichlid-free streams, and tested for evolutionary divergence in brain gene expression patterns after three to four generations. We find 135 transcripts that evolved parallel changes in expression within the replicated introduction populations. These changes are in the same direction exhibited in a native cichlid-free population, suggesting rapid adaptive evolution. We find 89% of these transcripts exhibited non-adaptive plastic changes in expression when the source population was reared in the absence of predators, as they are in the opposite direction to the evolved changes. By contrast, the remaining transcripts exhibiting adaptive plasticity show reduced population divergence. Furthermore, the most plastic transcripts in the source population evolved reduced plasticity in the introduction populations, suggesting strong selection against non-adaptive plasticity. These results support models predicting that adaptive plasticity constrains evolution (6-8), whereas non-adaptive plasticity potentiates evolution by increasing the strength of directional selection (11,12). The role of non-adaptive plasticity in evolution has received relatively little attention; however, our results suggest that it may be an important mechanism that predicts evolutionary responses to new environments., A long-standing problem in evolutionary biology is to understand the relationship between environmentally induced variation observed within a generation, and genetically-based evolutionary changes between generations (1-5). It has long been [...]

Evolutionary biologists have long sought to understand the relationship between microevolution (adaptation), which can be observed both in nature and in the laboratory, and macroevolution (speciation and the origin of the divisions of the taxonomic hierarchy above the species level, and the development of complex organs), which cannot be witnessed because it occurs over intervals that far exceed the human lifespan. The connection between these processes is also a major source of conflict between science and religious belief. Biologists often forget that Charles Darwin offered a way of resolving this issue, and his proposal is ripe for re-evaluation in the light of recent research., Charles Darwin and Alfred Russel Wallace based their insight that organisms evolve by natural selection on four principles (1,2): first, that organisms have 'individual variations' that are faithfully transmitted from [...]

Where the fish are greener? One of the trickiest problems in evolutionary biology is to explain how natural populations maintain an element of genetic diversity. Of all the proposed mechanisms, theory shows that frequency-dependent selection can be the most potent, yet there is only indirect evidence for its importance in natural populations. An experimental manipulation in natural populations of guppies now shows that there is a significant survival advantage for rare genotypes (exotic colouring in males) in natural populations of guppies. This is perhaps the best experimental evidence yet that frequency-dependent selection can be a potent mechanism maintaining genetic variation in natural populations. Results from an experimental manipulation showed a significant survival advantage for rare genotypes in natural populations of guppies, confirming that frequency-dependent selection can act as a potent mechanism in maintaining genetic variation in natural populations. The maintenance of genetic variation in traits under natural selection is a long-standing paradox in evolutionary biology.sup.1,2,3. Of the processes capable of maintaining variation, negative frequency-dependent selection (where rare types are favoured by selection) is the most powerful, at least in theory.sup.1; however, few experimental studies have confirmed that this process operates in nature. One of the most extreme, unexplained genetic polymorphisms is seen in the colour patterns of male guppies (Poecilia reticulata).sup.4,5. Here we manipulated the frequencies of males with different colour patterns in three natural populations to estimate survival rates, and found that rare phenotypes had a highly significant survival advantage compared to common phenotypes. Evidence from humans.sup.6,7 and other species.sup.8,9 implicates frequency-dependent survival in the maintenance of molecular, morphological and health-related polymorphisms. As a controlled manipulation in nature, this study provides unequivocal support for frequency-dependent survival--an evolutionary process capable of maintaining extreme polymorphism., Author(s): Robert Olendorf [sup.1] , F. Helen Rodd [sup.3] , David Punzalan [sup.3] , Anne E. Houde [sup.4] , Carla Hurt [sup.5] , David N. Reznick [sup.6] , Kimberly A. [...]

Author(s): David N. Reznick (corresponding author) [1]; Michael J. Bryant [1, 2]; Derek Roff [1]; Cameron K. Ghalambor [3]; Dionna E. Ghalambor [3] Classical theories [1, 2] for the evolution [...]

Author(s): David N. Reznick (corresponding author) [1]; Joseph Travis (corresponding author) [2] Adaptive evolution causes populations to evolve towards a body form that is best suited to the local environment. [...]

Author(s): Cameron K. Ghalambor; Kim L. Hoke; Emily W. Ruell; Eva K. Fischer; David N. Reznick; Kimberly A. Hughes Nature 525, 372375 (2015); doi:10.1038/nature15256 There are several errors in this [...]

Author(s): Cameron K. Ghalambor (corresponding author) [1, 2]; Kim L. Hoke [1, 2]; Emily W. Ruell [1]; Eva K. Fischer [1]; David N. Reznick [3]; Kimberly A. Hughes [4] REPLYING [...]