Ecological and evolutionary implications of phenotypic plasticity

Phenotypic plasticity seems to be adaptive and inherited across generations. Therefore, it can play a significant role in population dynamics and evolution. However, our understanding of the importance of adaptive transgenerational plasticity across different environmental factors and taxa is still limited. For example, plasticity might be even more important in perennial species with long life cycles, respect to annual plants (Walter et al., 2016; Herman and Sultan, 2011). In perennial species, genetic adaptation through natural selection could be indeed too slow to keep pace with rapid environmental changes (but see Yin et al., 2019 for more frequent adaptive transgenerational effects in annual plants).

Phenotypic plasticity may be an adaptive strategy also for clonal plants, as it can allow them to colonize new environments even with low standing genetic diversity. It may be particularly relevant also across clonal generations since it can be mediated by epigenetic mechanisms, which seem to be better maintained across clonal than sexual generations. The transgenerational effects mediated by heritable environmentally-induced epigenetic changes can, therefore, enable a rapid adaptation to changing environments, which infers implications in the short-term microevolution of clonal plants (Latzel and Klimešová, 2010; Verhoeven and Preite, 2014; Dodd and Douhovnikoff, 2016).

Notably, transgenerational plasticity gives rise to adaptive heritable variation precisely when required, as opposed to randomly occurring genetic variation (Verhoeven et al., 2010). Furthermore, particular environmental stress can induce the same adaptive phenotype in various offspring individuals in a population at the same time, as opposed to a phenotype based on genetic variation, which is shared only by part of the population. Consequently, populations can undergo rapid and extensive phenotypic adaptation based on transgenerational plasticity even in the absence of changes in the DNA sequence (Jablonka and Raz, 2009).

Transgenerational plasticity might be relevant also for understanding the ecological impacts of climate change, including global temperature and moisture changes predicted to arise very rapidly due to human activities (IPCC, 2014). Since adaptive transgenerational plasticity can be established even within one generation, it can shortly buffer populations against the immediate effects of climate change and provide time for genetic adaptation or genetic assimilation to act in the long run (Chevin, Lande, & Mace, 2010; Kopp & Matuszewski, 2014). For more details, refer to "Chapter 4: Epigenetics in evolution". In conclusion, our understanding of plant phenotypic plasticity has drastically improved in the last decades. Many phenotypic responses seem to be affected by epigenetic mechanisms, and they seem to facilitate plant adaptation to environmental changes. However, a vast majority of these phenotypic responses seem to be genotype-, species- and taxa-specific, which makes it hard to draw general conclusions on the role of epigenetically-driven phenotypic plasticity in plant adaptation. But then again, it is the nature of local adaptation that the effects are specific to the specific local environment and the genetic properties of the local population. There is thus the need to explore epigenetically-driven phenotypic responses across several genotypes, non-model plant species and taxa.