2013 – 2017: PhD thesis on community evolution in grasslands
My doctoral research in the group of Professor Bernhard Schmid at the University of Zurich (Switzerland) focused on the positive relationship between plant biodiversity and ecosystem functioning in a grassland biodiversity experiment (The Jena Experiment). I am especially interested in the mechanisms that might strengthen this relationship. I investigated how community evolution in plant communities can increase ecosystem functioning (i.e. community productivity) and ecosystem stability in response to a natural flooding event. In common garden experiments, I assessed whether selection in response to community diversity can alter community performance and plant functional traits in newly assembled test assemblages. In addition, I explored the role of below-ground community composition on plant biomass production and how co-evolution between soil organisms (e.g. AMF) and their associated plants alters ecosystem functioning.
Community Evolution increases Ecosystem Functioning and Stability (pdf)
For my first PhD chapter, we tested effects of community evolution on primary productivity in 48 different plant communities of 1, 2, 4 or 8 grassland species growin within the Jena Experiment. We found that productivity was increased if communities were assembled from plants that had previously been growing together for 8 years compared with communities assembled from plants without a common history. The observed positive effect of community evolution on productivity was independent of the presence of co-selected soil organisms but restricted to low diversity; mixtures of 8 species were not affected. We conclude that to preserve well-functioning ecosystems we need to protect interacting species in a community context.This research has recently been published in Ecology Letters.
In a second paper we tested wtheter community evolution also increased stability and resilience in these same communities in the Jena Experiment. We therefore assessed stability during unperturbed period and also resistance, resilience and recovery in response to a natural flooding event. This manuscript is in preparation and will be submitted soon.
Previously it was shown that differential selection in monoculture and mixed species grassland communities could lead to the rapid emergence of monoculture and mixture phenotypes (Zuppinger-Dingley et al, 2014).
For my PhD, we conducted a similar experiment showing that community diversity as selective environment can alter plant performance and functional traits. The manuscript can be found here on bioRxiv.
Underlying mechanisms for such rapid phenotypic responses are however still unclear. We hypothesize that in biodiversity experiments pre-adapted genotypes or epigenetic variants could be sorted out from the standing genetic or epigenetic variation.
To test if biodiversity acted as a selective environment, we grew offspring from plants that were exposed for twelve years to a monocultures or mixture environment under controlled greenhouse conditions. Using epiGBS, a genotyping by sequencing approach combined with bisulphite conversion to provide integrative genetic and epigenetic data, we showed that plants with a monoculture or mixture background were genetically distinct. Our data reveals a strong correlation between genetic and epigenetic variation and suggest genetic variation as driving force of most epigenetic variation. This pattern was consistently observed across different plant species. These results suggest that, in perennial grassland species, selection of genetic variation underlies the rapid emergence of monoculture and mixture types.
The corresponding manuscript is available on BioRxiv.
You can also find more information about this project in the following poster (presented at the 40th New Phytologist Symposium in Vienna, Austria).
Poster: Evidence for Rapid Evolution in Grasslands (pdf)
In a projectled by my PhD colleague Dr. Terhi Hahl we assessed in greenhouse experiments whether soil community history and plant selection history interact.
In two experiments we looked 1) at interactions between plants and mutualistic soil organisms (arbuscular mycorrhizal fungi) and 2) at soil microbial composition in response to plant diversity legacy effects.
The manuscript about the AMF experiment can be found here on BioRxiv.