Invasive Species Assessment Protocol: U.S. National Assessments Alternanthera sessilis ELEMENT NATIONAL ID: 235065 SCIENTIFIC NAME: Alternanthera sessilis COMMON NAME: I-RANK REVIEW DATE: 2006-04-13 EVALUATOR: Tomaino, A. I-RANK: Low/Insignificant I-RANK REASONS SUMMARY: An agricultural weed that invades disturbed wet areas in tropical and subtropical areas of the U.S. It is rare or occasional in scattered counties from eastern Texas to South Carolina but more common in Hawaii. Very little information was found about its impacts on native species habitats in the U.S. It is still available for sale. SUBRANK I - ECOLOGICAL IMPACT: Low/Insignificant SUBRANK II - CURRENT DISTRIBUTION/ABUNDANCE: Low SUBRANK III - TREND IN DISTRIBUTION/ABUNDANCE: High/Low SUBRANK IV - MANAGEMENT DIFFICULTY: Medium/Insignificant NON-NATIVE THROUGHOUT NATION NATIVE RANGE: China, Taiwan, Bhutan, India, Nepal, Cambodia, Laos, Myanmar, Thailand, Vietnam, Indonesia, Malaysia, Philippines (USDA 2005). SCREENING QUESTIONS S-1. ESTABLISHED OUTSIDE CULTIVATION AS A NON-NATIVE? YES COMMENTS: Established outside cultivation in the U.S. (Kartesz 1999). S-2. PRESENT IN CONSERVATION AREAS OR OTHER NATIVE SPECIES HABITATS? Yes COMMENTS: Occurs in wet disturbed areas (FNA 2003). SECTION I. ECOLOGICAL IMPACT 1. IMPACT ON ECOSYSTEM PROCESSES AND SYSTEM-WIDE PARAMETERS C/D - LOW SIGNIFICANCE/INSIGNIFICANT COMMENTS: No mention of changes in abiotic ecosystem processes or system-wide parameters found in the literature; assumption is that any alterations are not high or moderate. Data are from NatureServe's central databases as of June 29, 2006 Copyright © 2006 NatureServe 2. IMPACT ON ECOLOGICAL COMMUNITY STRUCTURE C/D - LOW SIGNIFICANCE/INSIGNIFICANT COMMENTS: Herbaceous annual or perennial with procumbent stems (FNA 2003). Up to 1 m tall (Scher 2004). No mention of impacts on ecological community structure found in the literature; assumption is that any impacts are not high or moderate. 3. IMPACT ON ECOLOGICAL COMMUNITY COMPOSITION C - LOW SIGNIFICANCE COMMENTS: No mention of impacts on ecological community composition found in the literature; assumption is that impacts are not high or moderate. 4. IMPACT ON INDIVIDUAL NATIVE PLANT OR ANIMAL SPECIES C/D - LOW SIGNIFICANCE/INSIGNIFICANT COMMENTS: No mention of impacts on ecological community composition found in the literature; assumption is that any impacts are not high or moderate. 5. CONSERVATION SIGNIFICANCE OF THE COMMUNITIES AND NATIVE SPECIES THREATENED B/D - MODERATE SIGNIFICNACE/INSIGNIFICANT COMMENTS: Occurs in wet disturbed areas (FNA 2003). It is a common weed in Hawaii (Wagner et al. 1999) so presumeably impacts some elements of conservation significance there. No mention of threats to elements of conservation significance found in the literature; assumption is that it is not often threatening elements of conservation significance. SECTION II. CURRENT DISTRIBUTION AND ABUNDANCE 6. CURRENT RANGE SIZE IN NATION C - LOW SIGNIFICANCE COMMENTS: Established in scattered counties from eastern Texas to South Carolina and on most of the islands of Hawaii; also reported from Maryland (J. Kartesz, unpublished data). 7. PROPORTION OF CURRENT RANGE WHERE THE SPECIES IS NEGATIVELY IMPACTING BIODIVERSITY B/C - MODERATE/LOW SIGNIFICANCE COMMENTS: It is a common weed in Hawaii and was first collected there in 1935 (Wagner et al. 1999). No mention of negative impacts on biodiversity found in the literature; assumption is that impacts occur in <50% of the species' current generalized range. 8. PROPORTION OF NATION'S BIOGEOGRAPHIC UNITS INVADED C - LOW SIGNIFICANCE COMMENTS: Inferred from distribution as currently understood (J. Kartesz, unpublished data; TNC 2001). Data are from NatureServe's central databases as of June 29, 2006 Copyright © 2006 NatureServe 9. DIVERSITY OF HABITATS OR ECOLOGICAL SYSTEMS INVADED IN NATION C - LOW SIGNIFICANCE COMMENTS: Damp shady areas, swamps, pond margins, shallow ditches, roadsides, low-lying waste places, damp pastures, cultivated areas (Scher 2004). It prefers wet conditions but occurs in both wetlands and uplands (Scher 2004). In Georgia and South Carolina, rare in disturbed wet muck on the coastal plain (Weakley 2006). In Florida, occasional on wet disturbed sites (Wunderlin and Hansen 2003). SECTION III. TREND IN DISTRIBUTION AND ABUNDANCE 10. CURRENT TREND IN TOTAL RANGE WITHIN NATION A/B - HIGH/MODERATE SIGNIFICANCE COMMENTS: It is still available for sale. Occurs in disturbed areas; assumption is that disturbed areas are not declining and therefore this species' total range is not declining. 11. PROPORTION OF POTENTIAL RANGE CURRENTLY OCCUPIED A - HIGH SIGNIFICANCE COMMENTS: Inferred from USDA (1990) and J. Kartesz, unpublished data. Apparently confined to tropical and subtropical areas. 12. LONG-DISTANCE DISPERSAL POTENTIAL WITHIN NATION A/B - HIGH/MODERATE SIGNIFICANCE COMMENTS: Alternanthera sessilis can be purchased as a water garden plant (Maki and Galatowitsch 2004). It is sold on the internet as an aquarium plant. Its seeds are also wind and water dispersed (Scher 2004). 13. LOCAL RANGE EXPANSION OR CHANGE IN ABUNDANCE A/C - HIGH/LOW SIGNIFICANCE COMMENTS: Occurs in disturbed areas; assumption is that disturbed areas are not decreasing or remaining stable and therefore this species' local range is not decreasing or remaining stable. 14. INHERENT ABILITY TO INVADE CONSERVATION AREAS AND OTHER NATIVE SPECIES HABITATS C - LOW SIGNIFICANCE COMMENTS: No mention of invasion of undisturbed habitats found in the literature. Occurs in wet disturbed areas (FNA 2003). In Georgia and South Carolina, rare in disturbed wet muck on the coastal plain (Weakley 2006). In Florida, occasional on wet disturbed sites (Wunderlin and Hansen 2003). 15. SIMILAR HABITATS INVADED ELSEWHERE C - LOW SIGNIFICANCE Data are from NatureServe's central databases as of June 29, 2006 Copyright © 2006 NatureServe COMMENTS: Wet disturbed areas in Mexico, West Indies, Central America, South America, Africa (FNA 2003). In New Guinea, "a plant of damp places; ditches, wet headlands, roadsides; sometimes a weed of plantations, particularly at altitudes of 1500 m or higher. From near sea level to over 2000m" (Henty & Pritchard 1975 cited by PIER 2005). In Tonga, "occasional as a waste area weed" (Yuncker 1959 cited by PIER 2005). 16. REPRODUCTIVE CHARACTERISTICS B/C - MODERATE/LOW SIGNIFICANCE COMMENTS: Spreads by seeds which are wind and water dispersed and by rooting at stem nodes (Scher 2004). SECTION IV. MANAGEMENT DIFFICULTY 17. GENERAL MANAGEMENT DIFFICULTY B/D - MODERATE SIGNIFICNACE/INSIGNIFICANT COMMENTS: No mention of control requiring a major long-term investment found in the literature; assumption is that a major long-term investment is not required. 18. MINIMUM TIME COMMITMENT B/D - MODERATE SIGNIFICNACE/INSIGNIFICANT COMMENTS: No mention of control requiring more than 10 years found in the literature; assumption is that control requires less than 10 years. 19. IMPACTS OF MANAGEMENT ON NATIVE SPECIES U - UNKNOWN COMMENTS: 20. ACCESSIBILITY OF INVADED AREAS C/D - LOW SIGNIFICANCE/INSIGNIFICANT COMMENTS: Classified as a noxious weed; assumption is accessibility problems are not severe or substantial. REFERENCES: Flora of North America Editorial Committee. 2003. Flora of North America North of Mexico, Volume 4, Magnoliophyta: Caryophyllidae, Part 1. Oxford University Press, New York. Kartesz, J.T. 1999. A synonymized checklist and atlas with biological attributes for the vascular flora of the United States, Canada, and Greenland. First edition. In: Kartesz, J.T., and C.A. Meacham. Synthesis of the North American Flora, Version 1.0. North Carolina Botanical Garden, Chapel Hill, N.C. Data are from NatureServe's central databases as of June 29, 2006 Copyright © 2006 NatureServe Maki, K. C., and S. M. Galatowitsch. 2004. Incidental Movement of Aquatic Organisms in Water Garden Sales. Abstract. In: Minnesota Water 2004: Policy and Planning to Ensure Minnesota's Water Supplies, March 23-24, 2004. East Bank Campus of the University of Minnesota. Online. Available: http://wrc.coafes.umn.edu/Water2004/Water2004_abstracts.html (accessed 4 January 2006). Pacific Island Ecosystems at Risk (PIER). 2005. December 19 last update. Alternanthera sessilis. United States Department of Agriculture Forest Service Institute of Pacific Island Forestry. Online. Available: http://www.hear.org/pier/species/sonchus_arvensis.htm (accessed 2006). Scher, J. 2004. Federal Noxious Weed disseminules of the U.S. Center for Plant Health Science and Technology, Plant Protection and Quarantine, Animal and Plant Health Inspection Service, U. S. Department of Agriculture. Online. Available: http://www.lucidcentral.org/keys/v3/FNW/ (Accessed 2006). The Nature Conservancy. 2001. Map: TNC Ecoregions of the United States. Modification of Bailey Ecoregions. Online <ftp://ftp.tnc.org/data/national/usa/tnc_us_eco2001.zip>. Accessed May 2003. USDA, ARS, National Genetic Resources Program. 2005. December 9 last update. Germplasm Resources Information Network (GRIN) Online Database. National Germplasm Resources Laboratory, Beltsville, Maryland. Available: http://www.ars-grin.gov2/cgi-bin/npgs/html/index.pl (Accessed 2006). USDA Agricultural Research Service. 1990. USDA Plants Hardiness Zone Map. Misc. Publ. Number 1475. Wagner, W.L., D.R. Herbst, and S.H. Sohmer. 1999. Manual of the flowering plants of Hawaii. Revised edition. Volumes 1 and 2. Univ. Hawaii Press and Bishop Museum Press, Honolulu. 1919 pp. Weakley, A. S. 2006. Flora of the Carolinas,