Weed Risk Assessment for Ipomoea United States biflora (L.) Pers. (Convolvulaceae) – Department of Bell vine Agriculture Animal and Plant Health Inspection Service February 18, 2015 Version 1 Ipomoea biflora (sources: left and bottom right: Bart Wursten; top right: Encyclopedia of Life (Encyclopedia of Life, 2014) Agency Contact: Plant Epidemiology and Risk Analysis Laboratory Center for Plant Health Science and Technology Plant Protection and Quarantine Animal and Plant Health Inspection Service United States Department of Agriculture 1730 Varsity Drive, Suite 300 Raleigh, NC 27606 Weed Risk Assessment for Ipomoea biflora Introduction Plant Protection and Quarantine (PPQ) regulates noxious weeds under the authority of the Plant Protection Act (7 U.S.C. § 7701-7786, 2000) and the Federal Seed Act (7 U.S.C. § 1581-1610, 1939). A noxious weed is defined as “any plant or plant product that can directly or indirectly injure or cause damage to crops (including nursery stock or plant products), livestock, poultry, or other interests of agriculture, irrigation, navigation, the natural resources of the United States, the public health, or the environment” (7 U.S.C. § 7701-7786, 2000). We use weed risk assessment (WRA)— specifically, the PPQ WRA model (Koop et al., 2012)—to evaluate the risk potential of plants, including those newly detected in the United States, those proposed for import, and those emerging as weeds elsewhere in the world. Because the PPQ WRA model is geographically and climatically neutral, it can be used to evaluate the baseline invasive/weed potential of any plant species for the entire United States or for any area within it. As part of this analysis, we use a stochastic simulation to evaluate how much the uncertainty associated with the analysis affects the model outcomes. We also use GIS overlays to evaluate those areas of the United States that may be suitable for the establishment of the plant. For more information on the PPQ WRA process, please refer to the document, Background information on the PPQ Weed Risk Assessment, which is available upon request. Ipomoea biflora (L.) Pers. – Bell vine Species Family: Convolvulaceae Information Synonyms: The taxonomy of this species may be unsettled; floras for Africa, Asia, and Malesia recognize two species; I. plebeia and I. sinensis. However, Chinese specimens called I. biflora are similar to what has been called I. plebeia in African and Malesian floras. The epithet biflora is well established in the Chinese literature and the authors describe it as a highly variable taxon (Fang and Staples, 1995). Aniseia biflora (L.) Choisy, A. calycina (Roxburgh) Choisy, Convolvulus biflorus L., C. hardwickii Spreng., C. plebeius (R. Br.) Spreng., C. ser Spreng., C. sinensis Desr., Ipomoea calycina Benth. Ex C.B. Clarke, I. hardwickii (Spreng.) Hemsl., I. plebeia R. Br., I. sinensis (Desr.) Choisy, I. timorensis Blume (Fang and Staples, 1995; The Plant List, 2013). Most sources for Africa and Australia used in this assessment refer to the synonym I. plebeia (Brisbane City Council, 2014; Graham, 2006; Hyde et al., 2014; NGRP, 2014; Sugar Research Australia, 2010). Common names: Bell vine (Sugar Research Australia, 2010), bellvine (Graham, 2006; NGRP, 2014). Botanical description: Ipomoea biflora is a twining or scandent annual herbaceous vine that grows 1 to 2 m tall. It is found in woodlands, grasslands, scrub, and ruderal habitats (Hyde et al., 2014); valleys, mountain slopes, and other dry habitats (Fang and Staples, 1995); and agricultural fields (Chivinge, 1988; Graham, 2006; Sugar Research Ver. 1 February 18, 2015 1 Weed Risk Assessment for Ipomoea biflora Australia, 2010). Initiation: APHIS received a market access request from South Africa for corn seeds for planting in the United States (South Africa DAFF, 2012). During the development of that commodity pest risk analysis, I. biflora was identified as a weed of potential concern to the United States. The PPQ Weeds Cross Functional Working Group decided to evaluate this species with a weed risk assessment. Foreign distribution: Ipomoea biflora is reported to be native to southern Africa and Asia, the Ryukyu Islands of Japan, and Australia (Fang and Staples, 1995; NGRP, 2014; Van Ooststroom and Hoogland, 1953). Its continent of origin is unclear. Ipomoea plebeia subsp. africana is reported as native to Africa, while subsp. plebeia is native to Australia and Malaysia (Hyde et al., 2014; Hyland et al., 2010); however, some sources describe the taxon I. biflora as native to all of these countries (Brisbane City Council, 2014; NGRP, 2014}). It is also known to occur in Papua New Guinea, and its nativity there is also unclear (Esso Highlands Limited, 2010). We found no evidence that it has been introduced elsewhere in the world. U.S. distribution and status: Ipomoea biflora is not known to occur as a weed or a cultivated plant in the United States or its territories (e.g., Kartesz, 2014; NGRP, 2014; NRCS, 2014). WRA area1: Entire United States, including territories. 1. Ipomoea biflora analysis Establishment/Spread Ipomoea biflora is an annual vine (Fang and Staples, 1995) that produces Potential viable seeds (DAFF, 2010; Johnson, 2006) and is a frequent seed contaminant of wheat and corn (DAFF, 2010; Emerald Grain, 2013). It inhabits several climate types and tolerates extreme precipitation (Fang and Staples, 1995; GBIF, 2014). Its score was reduced because it is not spread by wind, water, or birds or other animals, it is easily destroyed during cultivation, and its seedbank does not persist in agricultural sites (Graham, 2006). We had high uncertainty for this risk element due to a lack of information about the species’ life history. Risk score = 3 Uncertainty index = 0.24 Impact Potential In its current range, I. biflora is primarily a weed of cotton (Graham, 2006), wheat (Emerald Grain, 2013), sugar cane (Sugar Research Australia, 2010), and corn (Mashingaidze, 2004). It is a seed contaminant in Australia (DAFF, 2010; Emerald Grain, 2013). It can damage farm equipment (Graham, 2006) and its seeds are reportedly toxic to livestock (DAFF, 2010). Otherwise, we found no evidence that I. biflora negatively impacts natural systems or urban 1 “WRA area” is the area in relation to which the weed risk assessment is conducted [definition modified from that for “PRA area”] (IPPC, 2012). Ver. 1 February 18, 2015 2 Weed Risk Assessment for Ipomoea biflora and suburban areas. We had high uncertainty for this risk element due to a lack of information about its biology and ecology. Risk score = 2.1 Uncertainty index = 0.24 Geographic Potential Based on three climatic variables, we estimate that about 39 percent of the United States is suitable for the establishment of I. biflora (Fig. 1). This predicted distribution is based on the species’ known distribution elsewhere in the world and includes point-referenced localities and areas of occurrence. The map for I. biflora represents the joint distribution of Plant Hardiness Zones 7- 13, areas with nearly 0-100+ inches of annual precipitation, and the following Köppen-Geiger climate classes: tropical rainforest, tropical savanna, steppe, desert, Mediterranean, and humid subtropical. Our determination was based on georeferenced records from Africa, Asia, and Australia (GBIF, 2014), which were representative of reported occurrences in the literature. The area estimated as suitable in the United States likely represents a conservative estimate as it only uses three climatic variables. Other environmental variables, such as soil and habitat type, may further limit the areas in which this species is likely to establish. The adaptive potential of I. biflora may be high based on the broad range of environmental conditions it inhabits. These include grasslands, dry thickets, and areas with a pronounced dry season (Van Ooststroom and Hoogland, 1953); open forests, vine thickets, and monsoon forests (Hyland et al., 2010); mountain slopes, roadsides, (Fang and Staples, 1995), pastures, gardens, disturbed sites, and waste areas (Brisbane City Council, 2014). Additionally, it is a weed of dryland cropping areas (Osten et al., 2007). Entry Potential We found no evidence that I. biflora is present in the United States. This species does not appear to be cultivated. It is known to be a corn and wheat seed contaminant (DAFF, 2010; Emerald Grain, 2013), and this may be its only likely pathway for introduction into the United States. We had average uncertainty for this risk element. Risk score = 0.1 Uncertainty index = 0.15 Ver. 1 February 18, 2015 3 Weed Risk Assessment for Ipomoea biflora Figure 1. Predicted distribution of Ipomoea biflora in the United States. Map insets for Alaska, Hawaii, and Puerto Rico are not to scale. 2. Results and Conclusion Model Probabilities: P(Major Invader) = 10.9% P(Minor Invader) = 69.3% P(Non-Invader) = 19.8% Risk Result = Evaluate Further Secondary Screening = Evaluate Further Ver. 1 February 18, 2015 4 Weed Risk Assessment for Ipomoea biflora Figure 2. Ipomoea biflora risk score (black box) relative to the risk scores of species used to develop and validate the PPQ WRA model (other symbols). See Appendix A for the complete assessment. Figure 3. Model simulation results (N=5,000) for uncertainty around the risk score for Ipomoea biflora. The blue “+” symbol represents the medians of the simulated outcomes. The smallest box contains 50 percent of the outcomes, the second 95 percent, and the largest 99 percent. Ver. 1 February 18, 2015 5 Weed Risk Assessment for Ipomoea biflora 3. Discussion The result of the weed risk assessment for Ipomoea biflora is Evaluate Further, and the result of the secondary screening is also Evaluate Further (Fig. 2). Our conclusion was supported by the results of the uncertainty simulation (Fig. 3). Ipomoea biflora is a weed of agriculture in its known range and does not appear to have been introduced to areas outside of its native range. This lack of information about its behavior in new locations causes a high level of uncertainty about the risk of its introduction.