Do global change drivers affect evolutionary niche shifts in response to diversity-related plant-soil feedbacks?
Grasslands are among the most important ecosystems worldwide covering large land areas and hosting a huge number of species. However, during the last decades, diversity in grasslands has dramatically decreased in Central Europe due land use changes (intensification, abandonment) and climate change factors.
Recent meta-analyses across grassland biodiversity experiments have shown that biodiversity stabilizes ecosystem productivity and productivity-related services against climate events such as periods of drought (Isbell et al. 2015) and that complementarity among species is important to regulate grassland productivity, regardless of the influence of global change drivers such as drought or nutrient input (Craven et al. 2016).
However, little is known about the consequences of declining diversity for micro-evolutionary trajectories of the persisting species and their adaptive abilities to maintain various ecosystem services and processes, if for instance species interactions may be disrupted due to the loss of a diverse neighborhood. Experimental research has shown that the effects of diversity on ecosystem functions, such as primary productivity, intensify over time (Reich et al. 2012).
Only recently, however, it has been shown that changes in species diversity alters the selective environment that plants experience and this may in part explain the intensifying role of biodiversity through time as communities adapt to novel biotic interactions and environmental scenarios (Zuppinger-Dingley et al. 2014). Specifically, the selection pressure for greater niche complementarity among species is thought to be high in diverse plant communities (Zuppinger- Dingley et al. 2014).
However, interspecific selection for complementarity may trade-off with the selection for pathogen defense (Viola et al. 2010). Resultantly, the loss of plant diversity may change the selective environment to favor individuals that are able to minimize the accumulation of pathogens that is known to occur in plant monocultures (Schnitzer et al. 2011, Eisenhauer 2012, Kulmatiski et al. 2012, Maron et al. 2011).
However, it remains unclear (1) how rapid and pervasive local adaptations and microevolutionary niche shifts are in response to changing local species diversity, and (2) whether such diversity-related micro-evolutionary niche shifts affect the response of these species to global change drivers, such as drought and increased nitrogen deposition.
The promotion project will study how plant species are selected for i) specific antagonistic and mutualistic interactions with their historical soil biota (positive and negative plant-soil feedbacks) and ii) adaptive responses to the impact of global change drivers (drought, nitrogen deposition). We will test the following hypotheses:
(1) Species interactions with soil biota depend on their shared plant diversity and environmental histories, such that species are better adapted to their respective diversity environment. Species performance is weaker if individuals were transplanted in a different soil-environment.
(2) The effects of global change drivers on species performances are lower for individuals transplanted in their respective soil-environment than for species transplanted in different soil environment. In general, global change drivers have a stronger influence on performance of individuals growing in species-low communities than on individuals growing in species-high communities.