The study of phenotypic plasticity, the ability of a genotype to produce different phenotypes in response to environmental changes, has evolved significantly over the past few decades. Initially considered a nuisance in evolutionary studies, it is now a primary focus, with advancements in methods such as quantitative and molecular genetics, as well as modeling approaches. The article discusses major aspects of research on phenotypic plasticity, highlighting progress and areas requiring further attention. Key points include: 1. **From Nuisance to Paradigm**: Phenotypic plasticity is now recognized as crucial in understanding how organisms develop and interact with their environment. 2. **Genetic Variation and Heritability**: Extensive studies have shown genetic variation for plastic responses, but heritability estimates are challenging due to logistical and conceptual issues. 3. **Selection on Plasticity**: Natural selection can favor certain plastic responses, but understanding how and how often this occurs remains underexplored. 4. **Costs and Limits**: There are costs to maintaining plasticity, and limits to its adaptive potential, which are important for evolutionary theory. 5. **Genetic Correlations**: The role of genetic correlations in constraints is debated, with theoretical models suggesting they may not be informative. 6. **Mathematical Modeling**: Optimality, quantitative genetic, and gametic models have contributed to understanding the evolution of plasticity, with optimality models being particularly useful. 7. **Macroevolution by Plasticity**: Plasticity can facilitate macroevolution through genetic assimilation and phenotypic accommodation. The author suggests that while some areas, like the genetic basis of plasticity, have been settled, others, such as the costs and limits of plasticity, are areas of ongoing research. The field is moving towards more empirical studies of natural selection on plastic responses, which are logistically challenging but conceptually crucial.The study of phenotypic plasticity, the ability of a genotype to produce different phenotypes in response to environmental changes, has evolved significantly over the past few decades. Initially considered a nuisance in evolutionary studies, it is now a primary focus, with advancements in methods such as quantitative and molecular genetics, as well as modeling approaches. The article discusses major aspects of research on phenotypic plasticity, highlighting progress and areas requiring further attention. Key points include: 1. **From Nuisance to Paradigm**: Phenotypic plasticity is now recognized as crucial in understanding how organisms develop and interact with their environment. 2. **Genetic Variation and Heritability**: Extensive studies have shown genetic variation for plastic responses, but heritability estimates are challenging due to logistical and conceptual issues. 3. **Selection on Plasticity**: Natural selection can favor certain plastic responses, but understanding how and how often this occurs remains underexplored. 4. **Costs and Limits**: There are costs to maintaining plasticity, and limits to its adaptive potential, which are important for evolutionary theory. 5. **Genetic Correlations**: The role of genetic correlations in constraints is debated, with theoretical models suggesting they may not be informative. 6. **Mathematical Modeling**: Optimality, quantitative genetic, and gametic models have contributed to understanding the evolution of plasticity, with optimality models being particularly useful. 7. **Macroevolution by Plasticity**: Plasticity can facilitate macroevolution through genetic assimilation and phenotypic accommodation. The author suggests that while some areas, like the genetic basis of plasticity, have been settled, others, such as the costs and limits of plasticity, are areas of ongoing research. The field is moving towards more empirical studies of natural selection on plastic responses, which are logistically challenging but conceptually crucial.