Weed Risk Assessment for Hygrophila United States corymbosa (Blume) Lindau Department of (Acanthaceae) – Temple plant Agriculture Animal and Plant Health Inspection Service January 27, 2015 Version 1 . Photographs illustrating different forms of Hygrophila corymbosa (source: Ševčík, 2012). 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 Hygrophila corymbosa 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. Hygrophila corymbosa (Blume) Lindau – Temple plant Species Family: Acanthaceae Information Synonyms: Nomaphila corymbosa Blume. Common names: Temple plant (Mukherjee, 2011), staghorn (Gann et al., 2014), giant hygro (GBIF, 2014), starhorn (NRCS, 2014). Botanical description: Hygrophila corymbosa is a herbaceous aquatic plant that can grow either emerged or fully submerged. It has opposite leaves that are 8-10 cm long and 3-5 cm wide. The entire plant is covered with glandular hairs. Hygrophila corymbosa plants are highly variable and many different varieties exist (Kasselmann, 2003; Paffrath, 1979). Initiation: PPQ received a market access request for Hygrophila corymbosa, H. difformis, H. pinnatifida, and H. polysperma aquatic plants for propagation from the Ministry of Food, Agriculture and Fisheries of the Danish Plant Directorate (MFAF, 2009). These Hygrophila species are not native to the United States (NGRP, 2014) and may pose a threat to the United States. For example, H. polysperma is regulated as a U.S. Federal Noxious Weed (NRCS, 2014). Thus, the PERAL weed team initiated a weed risk assessment for H. corymbosa. Foreign distribution: This species is native to India (Paffrath, 1979) and southeast Asia (Windeløv, 2004) and introduced to and naturalized in Taiwan (Wu et al., 2010). It is cultivated in Europe (Windeløv, 2004). U.S. distribution and status: Hygrophila corymbosa has been cultivated in Ver. 1 January 27, 2015 1 Weed Risk Assessment for Hygrophila corymbosa aquariums in the United States since the 1970s (Rataj and Horeman, 1977). This species has recently naturalized in Florida in Hillsborough (USF Herbarium, 2014) and Broward counties (Gann et al., 2014; Kartesz, 2014) but is currently not regulated at the state or Federal level. WRA area1: Entire United States, including territories. 1. Hygrophila corymbosa analysis Establishment/Spread Hygrophila corymbosa is an aquatic plant that can grow either submerged or Potential emerged (Paffrath, 1979). This species has naturalized in Taiwan (Wu et al., 2010), and in Hillsborough (USF Herbarium, 2014) and Broward counties in Florida (Gann et al., 2014; Kartesz, 2014). Like other Hygrophila species, H. corymbosa easily re-roots from broken off plants or side-shoots and cut vegetative pieces (Aqualand, 2011; Paffrath, 1979). One aquarist on an aquatic plant message board noted that he or she had dumped waste aquarium water containing H. corymbosa cuttings into his or her yard and the plants then rooted and began growing emerged (Aquatic Plant Central, 2006). We had very high uncertainty here due to the lack of information on the biology of this species; we answered several questions with general information about the genus Hygrophila. Risk score = 13 Uncertainty index = 0.33 Impact Potential We found no information that H. corymbosa has caused negative impacts where it has naturalized. However, that may be because H. corymbosa has only very recently naturalized in new areas (Taiwan, Florida; see above). We answered most questions in this risk element as ‘unknown,’ resulting in an extremely high amount of uncertainty for this risk element. Risk score = 1.2 Uncertainty index = 0.62 Geographic Potential Based on three climatic variables, we estimate that about 10 percent of the United States is suitable for the establishment of H. corymbosa (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 H. corymbosa represents the joint distribution of Plant Hardiness Zones 9-13, areas with 0-100+ inches of annual precipitation, and the following Köppen-Geiger climate classes: tropical rainforest, tropical savanna, steppe, humid subtropical, and marine west coast. If grown submerged, H. corymbosa might be suitable for areas with <20 inches of precipitation, but we had high uncertainty about this. We had greater than average uncertainty for this section because we had very little geo-referenced point source data to use for this species. 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 January 27, 2015 2 Weed Risk Assessment for Hygrophila corymbosa The estimated area is likely 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. In Florida, H. corymbosa occurs in disturbed wetlands such as banks and canals (Gann et al., 2014). Entry Potential We did not assess the entry potential of H. corymbosa because it is already present in the United States (Kartesz, 2014; NRCS, 2014; USF Herbarium, 2014). Figure 1. Predicted distribution of H. corymbosa in the United States. Map insets for Alaska, Hawaii, and Puerto Rico are not to scale. 2. Results Model Probabilities: P(Major Invader) = 41.3% P(Minor Invader) = 54.5% P(Non-Invader) = 4.1% Risk Result = High Risk Secondary Screening = Not Applicable Ver. 1 January 27, 2015 3 Weed Risk Assessment for Hygrophila corymbosa .. Figure 2. Hygrophila corymbosa 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 H. corymbosa. 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 January 27, 2015 4 Weed Risk Assessment for Hygrophila corymbosa 3. Discussion The result of the weed risk assessment for H. corymbosa is High Risk. Hygrophila corymbosa received this result because it shares many establishment and spread traits with other known U.S. major invaders (Fig. 2). Even though our overall uncertainty for this risk assessment was very high, 86 percent of our simulated risk scores received a score of High Risk (Fig. 3). The Texas Parks and Wildlife Department conducted weed risk assessments for several Hygrophila species using a version of the Australian Weed Risk Assessment (Pheloung et al., 1999) modified for aquatic plants (Chilton, 2014). Hygrophila corymbosa received a score of 12 (Cook- Hildreth, 2014), well above the “reject” rating given to species with a score of 6 or higher. We found no evidence that H. corymbosa has had any negative impacts, but that may be because it has only very recently become naturalized in Taiwan (Wu et al., 2010) and Florida (Kartesz, 2014; USF Herbarium, 2014). Consequently, we have no information about the behavior of this species in those new areas. Hygrophila corymbosa is available for sale as a cultivated aquatic plant in aquariums and in outdoor ponds (Paffrath, 1979; Stokes et al., 2004; Windeløv, 2004). 4. Literature Cited 7 U.S.C. § 1581-1610. 1939. The Federal Seed Act, Title 7 United States Code § 1581-1610. 7 U.S.C. § 7701-7786. 2000. Plant Protection Act, Title 7 United States Code § 7701-7786. Amritphale, D., A. Gutch, and A. I. Hsiao. 1993. Acidification, growth promoter and red light effects on germination of skotodormant seeds of Hygrophila auriculata. Environmental and Experimental Botany 33(4):471-477. Aqualand. 2011. Temple Plant. Aqualand's inside scoop on Hygrophila corymbosa. Aqualand Fact Sheet. AqualandPetsPlus.com. Last accessed September 17, 2014, http://aqualandpetsplus.com/Plant,%20Temple%20Plant.htm. Aquatic Plant Central. 2006. Question about Hygrophila corymbosa "angustifolia" Aquatic Plant Central, General Interest Forums, General Aquarium Plants Discussions. Last accessed November 6, 2013, http://www.aquaticplantcentral.com/forumapc/general- aquarium-plants-discussions/14143-question-about-hygrophila- corymbosa-angustifolia.html. Champion, P. D., and J. S. Clayton. 2000. Border control for potential aquatic weeds. Stage 1. Weed risk model. Science for Conservation 141:1-48. Chandran, R. P., S. Manju, M. V. Vysakhi, P. K.