EvoPlast - Evolution of plant phenotypic plasticity in response to grassland management
Final Report Abstract
In my DFG project EvoPlast I explored the ability of plants to respond plastically, i.e. with immediate growth or physiological responses, to changing environmental conditions in the context of managed grasslands. In particular, I and my PhD student looked at whether populations from different grasslands varied in their ability to regrow after damage (mowing and grazing) and in their ability to make use of the sudden availability of plenty of nutrients (fertilization). Furthermore, we hypothesized that the strength of plant responses to these management activities correlated positively with landuse intensity; if farmers mow or fertilize more often, plants would evolve the ability to plastically respond to them in such a way that it helps to retain or increase fitness. We tested this hypothesis using three common grassland species which we sampled from dozens of grasslands varying strongly in management intensity. We grew offspring in two so-called common garden experiments and applied a fertilization treatment and a clipping treatment to half the plants respectively. By growing plants in common environmental conditions, genetically based variation in plastic responses can be revealed and this variation can be correlated with known land-use intensity values from the sites of origin. Although our common garden experiments revealed ample evidence for genetically based variation in the strength of regrowth ability and opportunistic responses to fertilization, this variation was hardly ever correlated with land-use intensity. The scarce relationships we found could be well explained from an eco-evolutionary viewpoint, e.g. mowing intensity and predictability drove some of the few relationships, which makes sense since mowing is clearly the most constant and spatially homogeneous land-use activity compared to grazing and fertilization. However, given the absence of relationships in most analyses, the overall conclusion from our experiments could be that land-use intensity is – against expectation – not a strong driver of ecologically relevant phenotypic plasticity in traits thought to be affected by land use. An alternative explanation could be that multiple environmental factors, including factors that we did not consider in our plasticity experiments, such as insect herbivore pressure or soil biota at the sites of origin, could interact with the assessed land-use practices and co-affect the evolutionary outcome of selection on the strength of plasticity. That plant populations can evolve in response to insect herbivory and soil biota became clear from a plant-soil feedback study we conducted within the framework of a collaboration, which is one of the few published studies looking at intraspecific variation in plant-soil feedback to this date. Plant-soil feedback means that plants grow better or worse when grown on their own soil compared to other soils, and at an intraspecific level implies that different plant populations respond differently to the soils they grow in. We found that plants grew better on foreign soil, and thus suggests that local soil adapts to local plants, to the detriment of the plant partner. Interestingly, this response was only observed under inclusion of natural insect herbivores, indicating that the level of realism in experimental settings is important for the outcome of studies. Another important finding from our fertilization experiment is that plants showing strong responses to fertilization were less able to retain nutrients under poor soil nutrient levels and vice versa. This result translates very well to the evolution of the plant strategies of acquisition versus conservation, which has been explored extensively among species but that only recently is being explored also at the intraspecific level. Finally, we measured the concentration of non-structural carbohydrates (NSC) in the roots of Plantago lanceolata (which can function as energy reserve for regrowth in spring or after damage) and we observed relationships with mowing intensity as well as temporal variation in mowing intensity at the sites of origin. This suggests that low mowing frequency and/or high predictability in mowing activity drives the evolution towards higher NSC storage and may allow plants to regrow after infrequent events of biomass removal or after the recurring annual mowing event. When mowing frequency is high or variable from year to year, plants do not evolve high NSC content, potentially because it is better to invest in aboveground tissue directly. To summarize, we found ample variation in plasticity of ecologically relevant traits in three grassland species in response to common land-use practices. However, this was mostly unrelated to land-use intensity, prompting the question what else drives this variation in plasticity.
Publications
- (2017) Evolution of plant phenotypic plasticity in response to grassland management. 27th annual meeting of the Plant Population Biology Specialist Group of the Ecological Society of Germany, Austria and Switzerland in Halle, Germany
Kirschbaum A, Scheepens JF
- (2019) Evolution of plant phenotypic plasticity in response to grassland management. Biennial Meeting of the European Society for Evolutionary Biology, in Turku, Finland
Kirschbaum A, Hoch G, Bossdorf O, Scheepens JF
- (2019) Evolution of plant phenotypic plasticity to grassland management. 27th Annual Meeting of the Plant Population Biology Specialist Group of the Ecological Society of Germany, Austria and Switzerland in Warsaw, Poland
Kirschbaum A, Bossdorf O, Scheepens JF
- Plant-soil feedbacks play a minor role in explaining intraspecific phenotypic variance under natural conditions. Frontiers in Ecology and Evolution 7:422
Kirchhoff L, Kirschbaum A, Joshi J, Bossdorf O, Scheepens JF, Heinze J
(See online at https://doi.org/10.3389/fevo.2019.00422) - (2021) Genetic variation in non-structural carbohydrates in Plantago lanceolata is related to mowing intensity but not to regrowth ability. EcoEvoRxiv
Kirschbaum A, Hoch G, Bossdorf O, Scheepens JF
(See online at https://doi.org/10.32942/osf.io/2q9aj) - (2021) Variation in regrowth ability in relation to landuse intensity in three common grassland herbs. Journal of Plant Ecology 14:438-450
Kirschbaum A, Bossdorf O, Scheepens JF
(See online at https://doi.org/10.1093/jpe/rtab001)
