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The Nonindigenous Occurrences section of the NAS species profiles has a new structure. The section is now dynamically updated from the NAS database to ensure that it contains the most current and accurate information. Occurrences are summarized in Table 1, alphabetically by state, with years of earliest and most recent observations, and the tally and names of drainages where the species was observed. The table contains hyperlinks to collections tables of specimens based on the states, years, and drainages selected. References to specimens that were not obtained through sighting reports and personal communications are found through the hyperlink in the Table 1 caption or through the individual specimens linked in the collections tables.

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Common name: duck-lettuce

Synonyms and Other Names: Stratiotes alismoides L., ducklettuce, duck lettuce

Taxonomy: available through www.itis.gov

Identification:

Habit: Ottelia alismoides is an annual or perennial herb, rooted, and completely submersed (Godfrey and Wooten 1979; Cook and Urmi-König 1984).

Stem/Roots: stem small and corm-like, occasionally forked, with fibrous roots (Cook and Urmi-König 1984).

Leaves: juvenile leaves somewhat linear, becoming oblanceolate, ovate or broadly cordate with maturity (Godfrey and Wooten 1979). Largest leaves from 11 to 16 cm long, their bases tapering to meet the petioles. Petioles of varying lengths (potentially up to 50 cm). Lower margins of leaves and edges of petioles often shallowly serrated to sharply toothed (Cook and Urmi-König 1984). Conspicuous longitudinal ribbing and cross-ribbing on the upper surface of the leaves gives a quilted effect (Cook et al. 1984).

Flowers: wrapped within spathes, cylindrical structures 2-4 cm long, composed of green bracts that are ornamented with 3 or more ruffled wings. Spathes born on long, angled stalks that become spiraled after flowering. Sepals and short-lived petals of male flowers exert from the tip of the spathe just above the water surface. Spathes containing female and/or bisexual flowers are self-fertile and remain submersed. Petals white, pink, blue or purple, often tinged with yellow at the base (Cook and Urmi-König 1984).

Fruit/Seeds: fleshy, encapsulated fruits contain as many as 2000 seeds (Cook and Urmi-König 1984).

Look-alikes: Alisma spp. (water plantain), Cryptocoryne spp. (water trumpet), Echinodorus spp. (burhead), Sagittaria spp. (arrowhead). Conspicuous cross-ribbing on the submersed leaves, and ruffled wings on flower bracts help distinguish this species (Cook et al. 1984; Cook and Urmi-König 1984).

Size: petioles and leaves combined up to 70 cm long (Cook and Urmi-König 1984)

Native Range: Tropical and warmer areas of Asia and Australia (Cook and Urmi-König 1984).

Alaska	Hawaii	Puerto Rico & Virgin Islands	Guam Saipan

Hydrologic Unit Codes (HUCs) Explained
Interactive maps: Point Distribution Maps

Ecology: Occurs along lake shorelines, marsh ponds, irrigation ditches and stream margins in water ranging from 5 cm to 1 m deep, occasionally floating if uprooted (Cook and Urmi-König 1984). Ottelia alismoides can tolerate moderate water level fluctuations, but fluctuations greater than 0.75 m may decrease viability (Yu and Yu 2009). It will act as an annual in ephemeral ponds and ditches, as O. allismoides does not have perrenating organs such as turions (Cook and Urmi-König 1984). In waters deeper than 0.8 m, the submerged flowers do not open (cleistogamous) and will self-fertilize if bisexual (Cook and Urmi-König 1984).

Seeds may remain viable for up to four years (Kaul 1978). Cook noted that fish prefer to eat the seeds, but it is unknown how this affects germination (Cook and Urmi-König 1984). Seeds will germinate in 25-30 °C, and germination may be influenced by light availability and burial depth, but substratum (mud or sand) and oxygen availability had no significant effect (Yin et al. 2013).

Means of Introduction: Propagules likely hitchhiked to North America with rice seed (Dike 1969). Migratory waterfowl are suspected to have transported propagules of O. alismoides to Big Cane Conservation Area in Butler County, Missouri (Yatskievych and Raveill 2001).

Status: Eradicated in California (Turner 1980); unknown status in Arkansas, Florida, Louisiana, Missouri, and Texas.

Impact of Introduction: The impacts of this species are currently unknown, as no studies have been done to determine how it has affected ecosystems in the invaded range. The absence of data does not equate to lack of effects. It does, however, mean that research is required to evaluate effects before conclusions can be made.

Remarks: Ottelia alismoides is a federally listed noxious weed in the United States (USDA 2016), while it is listed as threatened in its native range of China (Jiang and Kadono 2001; Yu and Yu 2009; Yin et al. 2013).

Ottelia alismoides requires constant water levels; its vegetation does not tolerate drying out. Unlike most other aquatic plants, this species lacks specialized organs for vegetative reproduction and reproduces solely by seed. Seed production is infallible because plants are autogamous and have a high reproduction allocation (Jiang and Kadono 2001; Cook and Urmi-König 1984). Dehiscent fruits release a floating, spongy mass containing seeds that eventually fall to the substrate (Cook and Urmi-König 1984). The floating mass released from the capsule has been observed to be consumed by fish, however it is not known if this affects seed germination or if fish are aiding in seed dispersal (Cook and Urmi-König 1984; Cook 1996).

*Special thanks to Northeast Louisiana University (NLU) Herbarium for loan of their Ottelia alismoides specimens.

Populations in Louisiana are believed to remain localized; a long established colony at Lake Chicot is still only about 18 m² in size (C. Dugas, pers. comm.). Where introduced to ricefields and agricultural irrigation ditches outside of the United States, Ottelia alismoides is not considered a serious weed (Cook 1996).

References: (click for full references)

Brown, L.E., and K.N. Gandhi. 1989. Notes on the flora of Texas with additions, range extensions and one correction. Phytologia 67(5):394-399.

Conner, W., C. Sasser, and N. Barker. 1986. Floristics of the Barataria Basin Wetlands, Louisiana. Castanea 51(2):111-128.

Cook, C.D.K. 1996. Aquatic Plant Book. SPB Academic Publishing, Amsterdam/New York. 228 pp.

Cook, C.D.K., J. Symoens and K. Urmi-König. 1984. A revision of the genus Ottelia (Hydrocharitaceae) I. Generic considerations. Aquatic Botany 18(3):263-274.

Cook, C.D.K., and K. Urmi-König. 1984. A revision of the genus Ottelia (Hydrocharitaceae). 2. The species of Eurasia, Australasia and America. Aquatic Botany 20(1-2):131-177.

Dike, D.H. 1969. Contribution to the biology of Ottelia alismoides (Hydrocharitaceae). Unpublished M.S. thesis. University of Southwestern Louisiana, Lafayette, LA.

Gentry, J.L. (director and curator). 2013. University of Arkansas Herbarium (UARK). University of Arkansas, Fayetteville, AR.

Godfrey, R.K. and J.W. Wooten. 1979. Aquatic and Wetland Plants of Southeastern United States, Monocotyledons. University of Georgia, Athens, GA. 712 pp.

Jiang, M. and Y. Kadono. 2001. Growth and reproductive characteristics of an aquatic macrophyte Ottelia alismoides (L.) Pers. (Hydrocharitaceae). Ecological Research 16: 687-695.

Kaul, R.B. 1978. Morphology of germination and establishment of aquatic seedlings in Alismataceae and Hydrocharitaceae. Aquatic Botany 5:139-147.

Marsico, T. (curator). 2013. Arkansas State University Herbarium (STAR). Arkansas State University, Jonesboro, AR. http://herbarium.astate.edu/.

Mast, A. (director), and K. Pearson (curator). 2014. Robert K. Godfrey Herbarium (FSU). Florida State University, Tallahassee, FL. http://herbarium.bio.fsu.edu/.

Perkins, K.D. (manager). 2015. University of Florida Herbarium (FLAS). University of Florida / Florida Museum of Natural History, Gainesville, FL. https://www.flmnh.ufl.edu/herbarium/.

Sasek, T. (curator), and D. Bell. 2007. University of Louisiana at Monroe Herbarium (NLU). University of Louisiana at Monroe, Monroe, LA. http://www.ulm.edu/herbarium/.

Solomon, J. (curator). 2015. Missouri Botanical Garden Herbarium (MO). Missouri Botanical Garden, St. Louis, MO. http://www.tropicos.org.

Thomas, R.D., and C.M. Allen. 1993. Atlas of the Vascular Flora of Louisiana. Vol I: Ferns and Fern Allies, Conifers, and Monocotyledons. Volume 1. Moran Colorgraphic Printing, Baton Rouge, LA.

Turner, C.E. 1980. Noteworthy collections: Ottelia alismoides. Madrono 27(4):177.

United States Department of Agriculture (USDA). 2016. Federal Noxious Weed List. United States Department of Agriculture. https://www.aphis.usda.gov/plant_health/plant_pest_info/weeds/downloads/weedlist.pdf.

Urbatsch, L.E. 2016. Shirley C. Tucker Herbarium (LSU). Louisiana State University, Baton Rouge, LA. http://www.herbarium.lsu.edu/plants.

Valentine, J.M. 1976. Plant succession after saw-grass mortality in southwestern Louisiana. Proceedings of the 13th Annual Conference. SE Assoc. Fish and Wildlife Agencies, 24-27 October 1976, Jackson, MS:634-640.

Yatskievych and Raveill. 2001. Additions and non-native angiosperms in Missouri, SIDA 19(3):706-708.

Yin, L., R. Zhang, Z. Xie, C. Wang, and W. Li. 2013. The effect of temperature, substrate, light, oxygen availability and burial depth on Ottelia alismoides seed germination. Aquatic Botany 111:50-53.

Yu, L., and D. Yu. 2009. Responses of the threatened aquatic plant Ottelia alismoides to water level fl uctuations. Fundamental and Applied Limnology 174(4):295-300.

Other Resources:
US Fish and Wildlife Service Ecological Risk Screening Summary for Ottelia alismoides

Author: Pfingsten, I.A.

This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.