This document summarizes a study that evaluated the risk of plant species introduced into botanical gardens becoming invasive weeds using a Weed Risk Assessment (WRA). The study analyzed data on plant introductions at two botanical gardens to compare risk scores between conservation species and horticultural introductions. It found conservation species had significantly lower and less variable risk scores than horticultural species. No species scored above the threshold for high risk of invasiveness. The study concludes the WRA is an effective tool for evaluating managed relocations of plant species into botanical gardens, especially when uncertainty exists about a species' risk of becoming invasive.

1. Weed risk assessment for botanical garden plant introductions:balancing the risks and benefits of ex situ conservation Hong Liu: Fairchild Tropical Botanic Garden Florida International University Chad Husby: Montgomery Botanical Center Sarah Reichard: University of Washington

2. Cultivation of food (ca. 12,000 BC) Cultivation of ornamental plants (1400 BC?) What are gardens for? Historically:

3. International Research and Conservation Fieldwork Paraguay Panama Trinidad and Tobago

4. Cycas micronesica Asian cycad scale arrived in Guam: 2003 As of 2007, less than 25% of C. micronesica population is left

6. Corypha taliera

7. Conservation through Cultivation Propagation of rare species ex situ can contribute substantially to conservation efforts Exchange of horticultural expertise and technology from such efforts can greatly enhance both in situ and ex situ conservation but…should we be cautious about introducing and propagating some rare species ex situ?

8. What are the risks of ex situ conservation introductions and other managed relocations (MR)? May behave as an invasive species or introduce associated pests or pathogens (Ricciardi and Simberloff, 2008)

9. Example of an endangered species that has become problematic ex situ Monterey pine (Pinus radiata): A rare declining species - 3 small California coastal populations - 2 island populations in Mexico Very popular plantation and landscape species Naturalized and invasive in southern hemisphere and northern California http://www.craigpine.co.nz/Seedlings.jpg

10. Botanical garden introductions 14 species of exotic mangroves introduced to Fairchild Tropical Botanic Garden (1940s-1980s) Most were hard to grow over the long term - often the case with plant introductions http://www.flickr.com/photos/edgley_cesar/3366002009/sizes/l/

11. Botanical garden introductions One escaped: Lumnitzera racemosa -showing weedy tendencies (Forquerean et al. 2009) http://ecobird.tncg.gov.tw/ecobird/warehouse/B00/971021030.jpg

12. Another barely persisted, but is not a problem:Bruguiera gymnorhizza http://www.efloras.org/gallery_image.aspx?flora_id=600&gallery_id=1091&image_id=1476 http://www.flickr.com/photos/ilmare77/3224619063/sizes/l/

13. Can we predict which species are a real risk? A priori approach: Not native = too risky Automatically “guilty” based on geographic origin location during a recent period of earth’s history Data driven approach Weed Risk Assessment Give species a multifaceted hearing – no a priori condemnation based on geographic origin Photo by Mike Bush

14. Why Managed Relocations (MR)? In situ conservation not always feasible Climate change may make this the only choice for many rare species Other types of habitat destruction and degradation – e.g. .deforestation, flooding, pollution

15. What is a weed? A “weed” does not exist objectively Concept of a weed flows from a combination of: Biological characteristics Ecological context History Human context

16. Australian WRA 49 Questions: Climate/distribution Domestication Weed elsewhere Undesirable traits for humans Plant type Reproduction Dispersal Persistence attributes <1 = not a pest 1-6 evaluate further > 6 = a pest

17. Sample Questions: Reproduction 6.01 Evidence of substantial reproduction failure in the native habitat 6.02 Produces viable seed 6.03 Hybridizes naturally 6.04 Self-compatible or apomictic 6.05 Require specialist pollinators 6.06 Reproduction by vegetatative fragmentation 6.07 Minimum generative time (years)

18. General Applicability Tested in New Zealand, Hawaii, Pacific Islands, Czech Republic, Bonin Islands, Florida Across sites 90% accurate in predicting invaders, 70% accurate with non-invaders Gordon et al. 2008

19. Casuarina vs. Gymnostoma:Pacific island WRA Casuarina equisetifolia: score = 21, High Risk Casuarina glauca: score = 20, High Risk Casuarina cunninghamiana: score = 12, High Risk Gymnostoma papuanum: score = 0, Low Risk

20. Gymnostoma papuanum in Hawaii Photo by Dr. J.B. Friday

21. Gymnostoma australianum http://swampythings.files.wordpress.com/2009/04/gymnostoma-australiana-11.jpg http://www.flickr.com/photos/tony_rodd/3719761173/

22. Testing the WRA for Managed Relocations in Botanical Gardens Data from ex situ introduced species in botanical gardens: Fairchild Tropical Botanic Garden (FTBG) Montgomery Botanic Center (MBC) Address two questions: Do threatened species have lower weed risk than non-threatened horticulturally introduced species? Can the WRA pick out the high risk species among the FTBG introductions?

23. Using the WRA for Botanic Garden Introductions Conservation species (22 spp.) Ex situ conservation from Caribbean, tropical America, Asia, etc. General horticultural species (22 spp.) Sale species promoted by FTBG to the general gardening public from 1955-1979 Matched with ex situ conservation species by habit (e.g., tree/shrub, palm, etc.)

24. Implementing the WRA Species evaluated using Florida WRA, risk scores calculated (1<not a problem, 1-6 evaluate further, >6 a problem) Data from FTBG/MBC records, internet and published sources, and field observations 3 evaluators, then checked for consistency

25. Weed risk scores T test Unequal variances p = 0.018

27. Diospyros maritimaa high-scoring horticultural introduction species Collected by David Fairchild from El Templo Island, Philippines Introduced into the Fairchild Garden in 1940 after Cheng-Ho Expedition Seedlings found recently in Matheson Hammock park, next to the Fairchild Tropical Botanic Garden Photo by Edward Beckwith Photo by Dr. Carl Lewis

28. Highest scoring: Sesbania punicea

29. Examples of low scoring species Croton fishlockii, Endemic to St. John Island (The US Virgin Islands) Buxus vahlii, Endemic to Puerto Rico; Virgin Islands (U.K.) - Anegada

30. Using the WRA for Garden Introductions Scores of conservation species varied significantly less than horticultural introduction species The conservation scores were substantially lower than the cut off point determining non-invasiveness Scores for both groups were low

31. General recommendation We recommend implementation of the Modified Australia Weed Risk Assessment Protocol as one of the tools to evaluate managed relocation Candidates: …especially when there is prior concern or uncertainty about the risks posed by a plant species

32. Acknowledgements Staff of FTBG (Mary Collins and Marilyn Griffiths) and MBC (Arantza Strader) are acknowledged for their help in providing data on the evaluated species. Jason Downing (Florida International University) helped with scoring, supported by Montgomery Botanical Center fellowship