Integrating Science and Management for Optimal Prevention and Control of Invasive Nymphoides in Florida

Science Center Objects

Two invasive species of floating hearts, Nymphoides cristata and N. indica, are actively managed in Florida. A rare native species, N. humboldtiana, has been found in Florida and verified by molecular methods; this species is nearly indistinguishable from N. indica.

Nymphoides: (a) N. humboldtiana (native) and (b) N. indica (invasive)

Easily confused Nymphoides of Florida including (a) N. humboldtiana (native) and (b) N. indica (invasive). Photos by Allain (USGS) and Tippery (UW Whitewater) respectively. Nymphoides indica seeds have bumps (reticules). (Credit: Allain (USGS), Tippery (UW Whitewater). Public domain.)

The Science Issue and Relevance: Two invasive species of floating hearts, Nymphoides cristata and N. indica, are actively managed in Florida. A rare native species, N. humboldtiana, has been found in Florida and verified by molecular methods; this species is nearly indistinguishable from N. indica. This study uses greenhouse experiments to assess carbon assimilation and other physiological responses to management strategies for the invasive floating heart species.

Methodology for Addressing the Issue: Mechanisms of plant oxygenation and CO2 uptake are studied in bell jars using an environmental gas monitor. The three Nymphoides species have different responses to CO2 deprivation, a technique that simulates the cutting of leaves, which is commonly used in aquatic plant management. The technique also provides information on the performance of these Nymphoides species in enhanced CO2 environments. N. humboldtiana depletes CO2 more rapidly than N. indica in greenhouse studies using experimental bell jars. However, both species deplete carbon rapidly, and therefore differ from N. cristata in their carbon uptake. Previous experiments show that the two exotic species (N. cristata and N. indica) respond differently to common invasive plant management strategies. Nymphoides indica dies when cut underwater, while N. cristata grows back rapidly.

Future Steps: The goal of this study is to determine if carbon uptake or other physiological strategies suggest new control strategies for N. cristata should be implemented. Life history dynamics and matrix modeling studies will be conducted when adult regeneration occurs in the greenhouse studies. This study will determine differences in leaf morphology to help managers differentiate between these species in the field, without relying on DNA analysis. Also, these studies will assess threats posed by invasive species control techniques on the rare native species, N. humboldtiana.

Related Projects: Nymphoides humboldtiana (Menyanthaceae) in Florida (USA) verified by DNA data; Morphology and genetics of Lythrum salicaria from latitudinal gradients of the Northern Hemisphere grown in cold and hot common gardens.