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Abstract Detail


Grewell, Brenda J. [1], Drenovsky, Rebecca [2], Skaer Thomason, Meghan J. [1], Futrell, Caryn J. [1], Iannucci, Maria [2].

Colonization ability of invasive Ludwigia congeners across resource gradients: diploid outperforms polyploid.

Understanding functional traits that underlie the colonization and niche breadth of invasive plants is key to developing sustainable management strategies to curtail invasions at the establishment phase. Emergent perennial Ludwigia species are among the world’s worst invasive aquatic plants, spreading rapidly by hydrochorous dispersal of asexual stolon or rhizome fragments. In a mesocosm experiment under static shallow water conditions, we evaluated the trait responses of two invasive Ludwigia congeners differing in ploidy (diploid, decaploid), when established as stolon ramets with contrasting soil nutrient availability (low, high) nested within light environments (shade, sun). Because polyploids are expected to have wider niche breadths than diploid ancestors, we predicted the decaploid species would have superior ability to maximize resource uptake and use, and out-perform a diploid congener. 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. Additional aquatic mesocosm experiments were conducted to compare the trait responses of standardized stolon and rhizome fragments differing in ploidy (diploid, decaploid) and subjected to 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 stolon 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. Overall, our experiments suggest the diploid species has a superior ability to maximize resource uptake, use and allocation across contrasting resource gradients in the early, colonizing phase of growth. 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.

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1 - USDA-ARS Exotic & Invasive Weeds Research Unit, Dept of Plant Sciences MS-4, University of California Davis, One Shields Avenue, Davis, CA, 95616, USA
2 - John Carroll University, Biology Department, 1 John Carroll Blvd, University Heights, OH, 44118, USA

aquatic plants
functional trait
invasion biology
invasive plants

Presentation Type: Oral Paper
Session: 22, Ecology Section: Invasive Species
Location: 103/Savannah International Trade and Convention Center
Date: Tuesday, August 2nd, 2016
Time: 8:30 AM
Number: 22002
Abstract ID:350
Candidate for Awards:None

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