Anyone who has studied biology at school or beyond will possibly remember that high diversity is believed to be an asset to any ecosystem, and to increase its productivity and resistance to disturbance. However, most studies of the effects of high diversity on ecosystems focus on diversity between species rather than diversity within the same species. Despite this, some studies have indicated that trait diversity within the same species (intraspecific diversity) also support high productivity and resilience of ecosystems.
It is unclear to what extent intraspecific trait diversity that benefits ecosystem productivity and resilience arises from genetic-driven diversity, or phenotypic diversity driven by environmental differences. Underpinning the latter may be epigenetics, reversible modifications of DNA that can be passed through generations. Puy and colleagues in their recent paper in Annals of Botany design a two-generation experiment using Arabidopsis thaliana to test the extent to which genetic diversity and environment-driven differences contribute to intraspecific diversity. They also consider how this may impact possible ecosystem resilience and productivity.
The authors use progeny populations of Arabidopsis plants of different genetic ecotypes. The parents were grown in either constant or variable environmental conditions. The progeny were then cultivated either as monocultures or mixtures in the next generation. Puy and colleagues find that mixed populations derived from parents grown in different environmental conditions have higher phenotypic diversity. A series of experiments confirm that this is effect is trans-generational (i.e. is inherited from the parent plants). Moreover, when chemical treatment was used to remove one particular type of epigenetic modification, the trait diversity of the mixed progeny populations was lost. This supports previous predictions that heritable phenotypic diversity driven by environmental differences is epigenetics-based, and may also be a substantial contributor to intraspecific diversity in ecosystems.
The authors also find that mixed populations with their epigenetic modifications reduced were less productive than monoculture populations, indicating that extreme loss of heritable environmentally-induced effects is detrimental to productivity in mixed communities. However, there was no effect to be found on productivity in genetically-diverse populations or populations of mixed environmental heritage that had not been treated to remove epigenetic modifications.
Whilst genetic and heritable environment-driven diversity may therefore not play a substantial role in productivity in these relatively short-term experiments using Arabidopsis plants, Puy and colleagues’ results do support a role for heritable epigenetic modification in environmentally-induced diverse traits that are important for productivity in mixed communities. As the authors speculate: ‘This aspect might be of particular importance in facing rapid environmental change since transgenerational effects have been increasingly recognized as determinants of successful adaptation of plants to novel climate’.