Genetic and epigenetic variation in natural populations across large spatial scales

Bárbara Díez Rodríguez

Summary

Genetic diversity can be defined as any measure that quantifies the magnitude of genetic variability within a population. In the last two decades, it has been shown to have a strong impact on populations, communities, and entire ecosystems (Rapp & Wendel, 2005; Kagiya et al., 2017). For example, genetic diversity reduces the rate at which species diversity declines in experimental grassland communities (Booth & Grime, 2003), increases species richness, and influences community composition in arthropod communities (Johnson et al., 2005; Witham et al., 2008; Robinson et al., 2012). The genetic diversity of dominant plant species can also affect nutrient flux, for instance, via litter decomposition processes (Bandau et al., 2016). On the other hand, phenotypic plasticity is defined as the ability of one genotype to produce more than one phenotype when exposed to different environments (Kelly et al., 2012). Intraspecific trait variability is a direct result of phenotypic plasticity and contributes to amplify the functional diversity of plant communities, a key component of biodiversity with important implications for species coexistence and ecosystem functioning (Medrano et al., 2014). Therefore, genetic diversity is the baseline for phenotypic diversity on which evolutionary processes like natural selection acts (Hughes et al., 2008). However, in recent years it became evident that epigenetic variation can play a role in phenotypic plasticity (Bossdorf et al., 2008; Heer et al., 2018), and several studies have suggested that epigenetic variation can create functional diversity in populations (Latzel et al., 2013). For example, epigenetic mechanisms play a role in allelopathy, and epigenetic changes might be more determinant than genetic variability in the success of plant invasions (Pérez et al., 2012; Hoffman, 2015; Slotkin, 2016). Furthermore, as explained in previous chapters, epigenetic variation can also have a role in how plants respond to environmental stress conditions (Kinosita & Seki, 2015). Although epimutations may arise spontaneously, a significant fraction of all epigenetic variation found within a population has a genetic and environmental basis (Kawakatsu et al., 2016). It is thus reasonable to assume that epigenetic variation can also influence populations and communities, and processes at the ecosystem or landscape levels.

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