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

• Published in: AoB PLANTS
• Main Authors: Harms, Nathan E, Cronin, James T, Gaskin, John F
• Other Authors: López, Lúa, U.S. Army Engineer Research and Development Center Aquatic Plant Control Research Program
• Format: Article in Journal/Newspaper
• Language: English
• Published: Oxford University Press (OUP) 2021
• Subjects: Butomus umbellatus
• Online Access: http://dx.doi.org/10.1093/aobpla/plab045; http://academic.oup.com/aobpla/advance-article-pdf/doi/10.1093/aobpla/plab045/39120757/plab045.pdf; http://academic.oup.com/aobpla/article-pdf/13/4/plab045/39650984/plab045.pdf

Abstract Separate introductions or post-introduction evolution may lead to multiple invader genotypes or cytotypes that differ in growth rates, biomass or chemical profile responses (phenotype) to a range of environments. If the invader has high trait plasticity to a range of resource levels, then sediment N or P enrichment may enhance invasiveness. However, the ways in which ploidy, plasticity, and available N or P interact are unknown for most species despite the potential to explain spread and impacts by invaders with multiple introduced lineages. We conducted a common garden experiment with four triploid and six diploid populations of Butomus umbellatus, collected from across its invasive range in the USA. Plants were grown under different N or P nutrient levels (4, 40, 200, 400 mg L−1 N; 0.4, 4, 40 mg L−1 P) and we measured reaction norms for biomass, clonal reproduction and tissue chemistry. Contrary to our expectation, triploid B. umbellatus plants were less plastic to variation in N or P than diploid B. umbellatus in most measured traits. Diploid plants produced 172 % more reproductive biomass and 57 % more total biomass across levels of N, and 158 % more reproductive biomass and 33 % more total biomass across P than triploid plants. Triploid plants had lower shoot:root ratios and produced 30 % and 150 % more root biomass than diploid plants in response to increases in N and P, respectively. Tissue chemistry differed between cytotypes but plasticity was similar; N was 8 % higher and C:N ratio was 30 % lower in triploid than diploid plants across levels of N and plant parts, and N was 22 % higher and C:N ratio 27 % lower across levels of P and plant parts. Our results highlight differences in nutrient response between cytotypes of a widespread invader, and we call for additional field studies to better understand the interaction of nutrients and ploidy during invasion.