Increased ploidy of Butomus umbellatus in introduced populations is not associated with higher phenotypic plasticity to N and P

Authors: HARMS, NATHAN - Us Army Corp Of Engineers (USACE); CRONIN, JAMES - Louisiana State University; Gaskin, John

Submitted to: AoBP (Annals of Botany PLANTS)
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/19/2021
Publication Date: 7/20/2021
Citation: Harms, N.E., Cronin, J.T., Gaskin, J.F. 2021. Increased ploidy of Butomus umbellatus in introduced populations is not associated with higher phenotypic plasticity to N and P. AoBP (Annals of Botany PLANTS). 13(4). Article plab045. https://doi.org/10.1093/aobpla/plab045.
DOI: https://doi.org/10.1093/aobpla/plab045

Interpretive Summary: An invasion can contain diverse genotypes. Nutrient enrichment (e.g., nitrogen (N) or phosphorus (P)) has been shown to favor some invaders over others. While increased ploidy is predicted to positively correlate with phenotypic plasticity, support for this relationship is mixed. Sediment N or P enrichment may contribute to invasiveness if a species (or genotype) has high plasticity to a range of resource levels. However, the ways in which ploidy, plasticity, and available N or P interact is unknown for most species despite the potential to explain the spread and subsequent impacts by invaders with multiple introduced lineages. We conducted a common garden experiment, in which ten populations (diploid and triploid ploidies) of the Eurasian invasive plant, Butomus umbellatus, were grown under different N or P nutrient levels (4, 40, 200, 400 mg/L N; 0.4, 4, 40 mg/L P). We measured reaction norms for biomass accumulation, vegetative reproduction, and tissue chemistry. Contrary to our expectation, triploid B. umbellatus plants were not more plastic to N or P overall. Diploid plants produced, on average, 300% more aboveground biomass and 250% more reproductive biomass at high [N] and 200% more aboveground biomass and 250% more reproductive biomass across [P]. In contrast, triploid plants produced 30% and 150% more underground biomass than diploid plants, in response to N and P, respectively. Tissue chemistry in response to N or P was similar between cytotypes for tissue C and P but tissue N was higher and C:N lower in triploid than diploid plants. Diploid plants outperformed triploid plants at all levels of P and all but the lowest N in biomass measures except underground biomass, which highlights the potential invasiveness of the diploid cytotype, especially in high-nutrient environments.

Technical Abstract: Separate introductions or post-introduction evolution in invasive species may generate multiple genotypes or result in varying ploidies that differ in their response (phenotype) to a range of environments. In particular, nutrient enrichment (e.g., N or P) has been shown to favor some invaders over others. While increased ploidy is predicted to positively correlate with phenotypic plasticity, support for this relationship is mixed. Sediment N or P enrichment may contribute to invasiveness if a species (or genotype) has high plasticity to a range of resource levels. However, the ways in which ploidy, plasticity, and available N or P interact is unknown for most species despite the potential to explain the spread and subsequent impacts by invaders with multiple introduced lineages. We conducted a common garden experiment, in which ten populations (diploid and triploid cytotypes) of the Eurasian invasive plant, Butomus umbellatus, were grown under different N or P nutrient levels (4, 40, 200, 400 mg/L N; 0.4, 4, 40 mg/L P). We measured reaction norms for biomass accumulation, vegetative reproduction, and tissue chemistry. Contrary to our expectation, triploid B. umbellatus plants were not more plastic to N or P overall. Diploid plants produced, on average, 300% more aboveground biomass and 250% more reproductive biomass at high [N] and 200% more aboveground biomass and 250% more reproductive biomass across [P]. In contrast, triploid plants produced 30% and 150% more underground biomass than diploid plants, in response to N and P, respectively. Tissue chemistry in response to N or P was similar between cytotypes for tissue C and P but tissue N was higher and C:N lower in triploid than diploid plants. Diploid plants outperformed triploid plants at all levels of P and all but the lowest N in biomass measures except underground biomass, which highlights the potential invasiveness of the diploid cytotype, especially in high-nutrient environments.