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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 #309093

Research Project: Aquatic and Riparian Weed Management to Protect U.S. Water Resources in the Far West United States

Location: Invasive Species and Pollinator Health

Title: Clonal integration in Ludwigia hexapetala under different light regimes

Author
item Glover, Rachel - John Carroll University
item Drenovsky, Rebecca - John Carroll University
item Futrell, Caryn
item Grewell, Brenda

Submitted to: Aquatic Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/16/2015
Publication Date: 1/20/2015
Citation: Glover, R., Drenovsky, R., Futrell, C.J., Grewell, B.J. 2015. Clonal integration in Ludwigia hexapetala under different light regimes. Aquatic Botany. 122:40-46.

Interpretive Summary: Improved understanding of the mechanisms underlying the ability of invasive plant species to establish and spread in novel environments is needed. The majority of plant species that invade natural aquatic and riparian habitats have a modular growth form known as “clonality”. These plants can reproduce asexually from fragments, spread quickly in flowing water, and establish new populations downstream. Clonal integration, through which connected ramets of clonal plants can share water, carbon compounds, and nutrients may contribute to their invasiveness. Physiological integration among ramets of invasive plant species may support their colonization and spread in novel aquatic environments where growth-limiting resources such as light are spatially heterogeneous. Under contrasting light conditions, we investigated the influence of clonal integration on the growth, biomass allocation and morphology of Ludwigia hexapetala, an emergent floating-leaved macrophyte highly invasive in a range of wetland habitat types. In aquatic mesocosms, stolons, connected ramets and severed ramets of parent and daughter plants were exposed to homogeneous or heterogeneous combinations of sun or 80% shade and growth responses were assessed. Morphological traits of all ramets were strongly influenced by light environment, and low light availability decreased plant growth regardless of integration status. Allocation patterns varied with light regime; shaded plants increased aboveground biomass while sun plants allocated more resources to below ground growth. Daughter ramets integrated with parents produced more biomass suggesting a fitness advantage through integration. However, parent ramet performance declined with stoloniferous integration; integrated parents produced fewer ramets and allocated more resources to belowground biomass. For most response variables measured, there was no significant interactive effect between light treatment and integration though parents growing in the shade attached to a daughter in the sun increased root mass ratio. The ability to establish and spread into new environments is a key trait of invasive plants, and physiological integration of resources may improve the establishment of juvenile ramets across variable light environments during early colonization. Physiological integration in patchy light environments may contribute to the invasiveness of Ludwigia hexapetala. Results suggest restoration of riverine habitats to increase shade may be a useful component of an integrated weed management strategy.

Technical Abstract: Physiological integration among ramets of invasive plant species may support their colonization and spread in novel aquatic environments where growth-limiting resources are spatially heterogeneous. Under contrasting light conditions, we investigated how clonal integration influences growth, biomass allocation and morphology of Ludwigia hexapetala, an emergent floating-leaved macrophyte highly invasive in a range of wetland habitat types. In aquatic mesocosms, stolons of offspring ramets were either connected or severed from parent plants, with the pairs exposed to homogenous or heterogeneous combinations of sun or 80% shade. Morphological traits of all ramets were strongly influenced by light environment, and low light availability decreased plant growth, regardless of integration status. Allocation patterns varied with light regime; shaded plants increased aboveground biomass while sun plants allocated more resources to belowground growth. Offspring ramets integrated with parents produced more biomass, suggesting a fitness advantage through integration. However, parent ramet performance declined with stoloniferous integration; integrated parents produced fewer ramets and allocated more resources to belowground biomass. For most response variables measured, there was no significant interactive effect between light treatment and integration, though parents growing in the shade attached to an offspring in the sun increased root mass ratio. The ability to establish and spread into new environments is a key trait of invasive plants, and physiological integration of resources may improve the establishment of juvenile ramets across variable light environments during early colonization. Physiological integration in patchy light environments may contribute to the invasiveness of Ludwigia hexapetala.