The genetic diversity of plant species and populations is generally considered the chief determinant of evolutionary change, with reduced diversity posing a threat to their long-term survival. Epigenetic diversity is now recognized as another layer of heritable variation with potential adaptive consequences. Epigenetic variation results from DNA methylation and modified chromatin state and are often inherited over generations in plant populations. One defining feature that sets epigenetic variation apart from genetic variation is the capacity to exhibit modifications in response to environmental factors. This suggests that epigenetic diversity could sometimes alleviate loss of genetic diversity and provide an “evolutionary backup” mechanism for wild plants faced by environmental stress.
In their new study in AoBP, Medrano et al. investigate this hypothesis by comparing the genetic and epigenetic diversity of seven cogeneric species pairs in south-eastern Spain. Each pair comprised one endemic species with a restricted range occupying stressful environments and one with a widespread distribution occupying more favourable habitats. All populations studied exhibited moderate to high levels of genetic polymorphism. However, contrary to expectations, populations of restricted endemic and widespread species did not differ in average genetic or epigenetic diversity in the study region. These results suggest that higher epigenetic diversity could alleviate the loss of genetic diversity in some populations of endemic plants, but other plant features are essential to fully understanding the relationship between genetic and epigenetic diversities. The authors suggest that further work should focus on the effects that other intrinsic plant traits (e.g. lifeform) and population features (e.g. size, isolation) may have in comparative multispecies patterns of genetic and epigenetic co-variation in this Mediterranean hotspot region or elsewhere.
This articles was published as part of the AoBP Special Issue entitled The Ecology And Genetics Of Population Differentiation In Plants.
Mónica Medrano is a researcher in Plant Sciences currently working at Doñana Biological Station from the Spanish National Research Council, whose research is motivated by the fundamental question of understanding how plants interact with and adapt to their biotic and abiotic environment. In her earlier career she tried to answer questions related to floral evolution, sexual reproductive strategies, and how certain floral traits influence mating systems in flowering plants. She has addressed also issues related to population genetics and conservation of endemic plants. More recently, she have been involved in a line of research that aims to elucidate the role of epigenetic processes in natural populations and communities, and evaluate the importance of epigenetics in micro- and macro-evolutionary processes in Angiosperms.