Resprouting potential of rhizome fragments from invasive macrophyte reveals superior colonization ability of the diploid congener

Authors: Grewell, Brenda; Futrell, Caryn; IANNUCCI, MARIA - John Carroll University; DRENOVSKY, REBECCA - John Carroll University

Submitted to: AoB Plants
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/6/2019
Publication Date: 10/22/2019
Citation: Grewell, B.J., Futrell, C.J., Iannucci, M., Drenovsky, R.E. 2019. Resprouting potential of rhizome fragments from invasive macrophyte reveals superior colonization ability of the diploid congener. AoB Plants. 11(6). https://doi.org/10.1093/aobpla/plz071.
DOI: https://doi.org/10.1093/aobpla/plz071

Interpretive Summary: Aquatic emergent Ludwigia species from a polyploid complex are among the world’s worst invasive aquatic plants. These perennial floating-leaved species respond to disturbance through fragmentation of either asexual shoot or rhizome fragments, and spread rapidly by hydrochorous dispersal. While recruitment of clonal aquatic plant species from shoot fragmentation is well documented, regeneration from rhizome bud banks is common yet often overlooked. Two aquatic mesocosm experiments were conducted to compare trait responses of Ludwigia congeners differing in ploidy (diploid, decaploid), grown from clonal fragments (shoot, rhizome) under contrasting soil nutrient availability (low, high). In this establishment stage of growth, the expectation that the decaploid would produce more biomass than diploid congener from either shoot or rhizome fragments was not supported. Both cytotypes were most responsive to nutrient availability when sprouted from rhizomes. Polyploid rhizomes had twice the nonstructural carbohydrate reserves than diploids at the start of the experiment, yet the diploids were more efficient in utilizing stored reserves for biomass production. Diploid rhizomes produced much higher total biomass with increased nutrient availability than polyploid plants from either fragment type, irrespective of nutrient availability. However, the primary shoot length of the polyploid exceeded that of the diploid under high nutrient availability suggesting greater spatial foraging potential. Our experiments suggest the diploid species has a superior ability to maximize resource uptake, use and allocation across contrasting resource gradients when regenerated from clonal fragments. Management strategies to prevent bank erosion and other disturbances that could produce and mobilize rhizome fragments are warranted. Biocontrol organisms that directly deplete below ground storage reserves or significantly reduce translocation of carbon to below ground storage organs could potentially enhance integrated management strategies. The highly invasive decaploid L. hexapetala invests heavily in shoot elongation that can enhance foraging ability for limited resources in heterogeneous environments. For these polyploids, management options such as mechanical removal or biocontrol agents that reduce shoot biomass improve management. Management strategies should prioritize rapid response to newly colonizing diploid invaders, and reductions in nutrient loads to aquatic environments may be more effective toward controlling establishment of the diploid congener than the decaploid.

Technical Abstract: Aquatic emergent Ludwigia species from a polyploid complex are among the world’s worst invasive aquatic plants. These perennial floating-leaved species respond to disturbance through fragmentation of either asexual shoot or rhizome fragments, and spread rapidly by hydrochorous dispersal. While recruitment of clonal aquatic plant species from shoot fragmentation is well documented, regeneration from rhizome bud banks is common yet often overlooked. Aquatic mesocosm experiments were conducted to compare trait responses of Ludwigia congeners differing in ploidy (diploid, decaploid), grown from clonal fragments (shoot, rhizome) under contrasting soil nutrient availability (low, high). In this establishment stage of growth, the expectation that the decaploid would produce more biomass than diploid congener from either shoot or rhizome fragments was not supported. Both cytotypes were most responsive to nutrient availability when sprouted from rhizomes. Polyploid rhizomes had twice the nonstructural carbohydrate reserves than diploids at the start of the experiment, yet the diploids were more efficient in utilizing stored reserves for biomass production. Diploid rhizomes produced much higher total biomass with increased nutrient availability than polyploid plants from either fragment type, irrespective of nutrient availability. However, the primary shoot length of the polyploid exceeded that of the diploid under high nutrient availability suggesting greater spatial foraging potential. Our experiments suggest the diploid species has a superior ability to maximize resource uptake, use and allocation across contrasting resource gradients when regenerated from clonal fragments. Management strategies should prioritize rapid response to newly colonizing diploid invaders, and reductions in nutrient loads to aquatic environments may be more effective toward controlling establishment of the diploid congener than the decaploid.