Genome size and ploidy influence angiosperm species' biomass under nitrogen and phosphorus limitation

Angiosperm genome sizes (GS) range c. 2400‐fold, and as nucleic acids are amongst the most phosphorus‐ (P) and nitrogen (N)‐demanding cellular biomolecules, we test the hypothesis that a key influence on plant biomass and species composition is the interaction between N and P availability and plant GS. We analysed the impact of different nutrient regimes on above‐ground biomass of angiosperm species with different GS, ploidy level and Grime's C‐S‐R (competitive, stress‐tolerant, ruderal) plant strategies growing at the Park Grass Experiment (Rothamsted, UK), established in 1856. The biomass‐weighted mean GS of species growing on plots with the addition of both N and P fertilizer were significantly higher than that of plants growing on control plots and plots with either N or P. The plants on these N + P plots are dominated by polyploids with large GS and a competitive plant strategy. The results are consistent with our hypothesis that large genomes are costly to build and maintain under N and P limitation. Hence GS and ploidy are significant traits affecting biomass growth under different nutrient regimes, influencing plant community composition and ecosystem dynamics. We propose that GS is a critical factor needed in models that bridge the knowledge gap between biodiversity and ecosystem functioning.