Evidence for rapid evolution in a grassland biodiversity experiment

In long-term grassland biodiversity experiments positive effects of biodiversity on plant productivity commonly increase with time. It has been shown that such increased biodiversity effects persist even if plants are transferred into a common environment. Thus, we hypothesized that community diversity had acted as a selective agent, which resulted in the emergence of plant monoculture and mixture types. To test our hypothesis, we grew offspring from plants that were exposed for eleven years to a monoculture or mixture environment in a biodiversity experiment (Jena Experiment) under controlled greenhouse conditions in monocultures or two-species mixtures. We used epiGBS, a genotyping-by-sequencing approach combined with bisulfite conversion to provide integrative genetic and epigenetic data. We observed significant genetic and epigenetic divergence according to selection history in three out of five perennial grassland species, namely Galium mollugo, Prunella vulgaris and Veronica chamaedrys. For a fourth species, Lathyrus pratensis, we found mixed evidence and a fifth one, Plantago lanceolata, did not exhibit any divergence. In addition, current diversity levels in the greenhouse also had weak effects on epigenetic variation. Our results suggest that selection of genetic variants, and possibly epigenetic variants, caused the rapid emergence of monoculture and mixture types within plant species in the Jena Experiment. However, given the limited genome coverage, it remains unclear how much of the epigenetic divergence was independent of the genetic divergence.