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ARS Home » Pacific West Area » Albany, California » Western Regional Research Center » Invasive Species and Pollinator Health » Research » Publications at this Location » Publication #323449
Title: Trait responses of invasive aquatic macrophyte congeners: colonizing diploid outperforms polyploid

Author
item Grewell, Brenda
item Skaer Thomason, Meghan
item Futrell, Caryn
item IANNUCCI, MARIA - John Carroll University
item DRENOVSKY, REBECCA - John Carroll University

Submitted to: AoB Plants
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/13/2016
Publication Date: 2/26/2016
Citation: Grewell, B.J., Skaer Thomason, M.J., Futrell, C.J., Iannucci, M., Drenovsky, R. 2016. Trait responses of invasive aquatic Ludwigia congeners (Onagraceae): effects of ploidy and resource availability. AoB Plants. 8:plw014. doi :10.1093/aobpla/plw014.

Interpretive Summary: Understanding functional traits underlying colonization and niche breadth of invasive plants is key to developing sustainable management solutions to curtail invasions at the establishment phase, when efforts are often most effective. The aim of this experimental study was to evaluate how two invasive congeners differing in ploidy (numbers of chromosomes in cells) respond to high and low resource availability following establishment from asexual fragments. Because polyploids are expected to have wider niche breadths than diploid ancestors, we predicted that a decaploid species (Ludwigia hexapetala; chromosomes 2n=80) would have superior ability to maximize resource uptake and use, and out-perform a diploid congener (Ludwigia peploides subsp. montevidensis; chromosomes 2n = 16) when colonizing environments with contrasting light and nutrient availability. A mesocosm experiment was designed to test the main and interactive effects of ploidy (diploid, decaploid) and soil nutrient availability (low, high) nested within light environments (shade, sun) of the two invasive aquatic plant congeners. Counter to our predictions, the diploid congener out-performed the decaploid in the early stage of growth. Although growth was similar and low in the cytotypes at low nutrient availability, the diploid species had much higher growth rate and biomass accumulation than the polyploid with nutrient enrichment, irrespective of light environment. This result suggests reductions in nutrient loads to aquatic environments may be more effective towards controlling the diploid congener than the decaploid. Our results also revealed extreme differences in time to anthesis between the cytotypes. The rapid growth and earlier flowering of the diploid congener relative to the decaploid congener represents alternate strategies for establishment and success. This temporal growth pattern suggests managers should target L. p. subsp. montevidensis for control early in the growing season. In contrast, the measured trait responses of L. hexapetala suggest its greater invasive spread and eventual displacement of native species is supported by a more long-term investment in growth, as early investment in shoot extension and rooting node production may support both asexual dispersal and foraging for heterogeneous resources. The unexpected outcomes from this experiment highlight the importance of multifactor manipulative experiments, as they provided a more mechanistic understanding of potentially interacting factors.

Technical Abstract: Understanding traits underlying colonization and niche breadth of invasive plants is key to developing sustainable management solutions to curtail invasions at the establishment phase, when efforts are often most effective. The aim of this study was to evaluate how two invasive congeners differing in ploidy respond to high and low resource availability following establishment from asexual fragments. Because polyploids are expected to have wider niche breadths than diploid ancestors, we predicted that a decaploid species would have superior ability to maximize resource uptake and use, and out-perform a diploid congener when colonizing environments with contrasting light and nutrient availability. A mesocosm experiment was designed to test the main and interactive effects of ploidy (diploid, decaploid) and soil nutrient availability (low, high) nested within light environments (shade, sun) of two invasive aquatic plant congeners. Counter to our predictions, the diploid congener out-performed the decaploid in the early stage of growth. Although growth was similar and low in the cytotypes at low nutrient availability, the diploid species had much higher growth rate and biomass accumulation than the polyploid with nutrient enrichment, irrespective of light environment. Our results also revealed extreme differences in time to anthesis between the cytotypes. The rapid growth and earlier flowering of the diploid congener relative to the decaploid congener represents alternate strategies for establishment and success. The unexpected outcomes from this experiment highlight the importance of multifactor manipulative experiments, as they provided a more mechanistic understanding of potentially interacting factors.