Phenotypic Plasticity

             To study evolutionary process, it is important to consider the effects of the environment on the process of development. Phenotypic plasticity is the capability of genotypes to response to environmental alterations. Thus, they can modify their phenotypic expression with morphological or physiological adjustments. Some responses are unavoidable, for example, the decrease in growth under adverse conditions for the development. According to Scheiner (1993), variances in allelic expression across environments and changes in interactions among loci are likely the causes of plasticity in a genetic level.

             As it can be seen in the figure 1 (Scheiner, 1993), the environment influences evolutionary processes in two ways. Firstly, it determinates the fitness of an individual’s phenotype by natural selection. In the second way, it establishes the phenotype interacting with the developmental process. Thus, the environment may change the phenotypic expression of a genotype (phenotypic plasticity). Additionally, the figure shows three sources of phenotypic variation: the genome, the environment and random accidents of development. These random processes are due to internal events that causes change; it is distinct from the environmental interaction. Therefore, Scheiner supposes that different phenotypes may come from genetically identical individuals grown in identical environments.

               

Figure 1 (Schiner, 1993) 

                It is important to clarify that plasticity is specific to a trait instead of an entire genotype. Some traits may be plastic responding to certain environment, while another may not. There are labile and fixed traits. The labile ones get change as fast as the environment while some traits are fixed during development such as size following metamorphosis in holometabolous insects. (Scheiner, 1993)

                 Scientists try different measures to quantify the phenotypic plasticity. To know if the plasticity of a trait is adaptive, it is measured the relationship between the trait plasticity and fitness averaged across environments. Despite, the study of phenotypic responses across more than two environments may be complex. The interests in these analyses are to compare populations and to predict responses to selection. The probable processes of adaptation to environmental stress resulting from plasticity could provide predictions about species responses to the climate change. Therefore, these studies could be the key to ensure the stability of populations before global changes.  

                Given this information, do you think it is possible to predict species responses to selection? Could we predict the behaviour of populations before global change? What do you think about the importance of plasticity?

REFERENCE LIST

Scheiner, SM 1993, ‘Genetics and evolution of phenotype plasticity’, The Annual Review of Ecology, Evolution, and Systematics, no. 24, pp. 35-68.