Ron Vanderhoff

Acacia longifolia Risk Assessment

Common names: Sydney golden wattle

Acacia longifolia -- California

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Evaluation Summary
Acacia longifolia (Sydney golden wattle) is a plant native to eastern Australia that has become invasive in several areas worldwide, including California. The plant is a shrubby tree that can form thickets that may be problematic. Though the seeds are not adapted for long-distance dispersal, they are plentiful and have some dormancy that allows the plant to form massive seedbanks, making long-term control difficult unless early eradication is possible.
General Evaluation Information
Date of Evaluation: 
January 1, 2020
Evaluation Time (hrs): 
3 Hours
Evaluation Status: 
Submitted
Plant Information
Plant Material: 
If the plant is a cultivar, and if the cultivar's behavior differs from its parent's (behavior), explain how: 
Regional Information
Region Name: 
Climate Matching Map
These maps were built using a toolkit created in collaboration between GreenInfo Network, PlantRight, Cal-IPC, and Agricultural Sustainability Institute at UC Davis.
Climate Matching Maps PDF: 
AttachmentSize
PDF icon Matching_Results.pdf515.31 KB
Invasive History and Climate Matching
1. Has the species (or cultivar or variety, if applicable; applies to subsequent "species" questions) become naturalized where it is not native?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
Very High
Answer / Justification: 
Yes, the species has naturalized in South Africa, Australia (Western Australia), New Zealand, Europe (France), the southwestern US, and South America (Brazil, Argentina, Uruguay). [USDA GRIN]
Reference(s): 
2. Is the species (or cultivar or variety) noted as being naturalized in the US or world in a similar climate?
Yes or No: 
Yes
Points: 
2
Confidence Level: 
Very High
Answer / Justification: 
The following areas where the species has naturalized are similar to the climate of the focal area (California, USA): USA (California), South Africa, Southern Europe (Spain, Portugal, southern France, Italy), Western Australia (disjunct from native range). (GBIF) The following areas where the species has naturalized are dissimilar in climate: New Zealand (North Island), South America (east coast of Argentina, Uruguay, Colombia)
Reference(s): 
3. Is the species (or cultivar or variety) noted as being invasive in the U.S. or world?
Yes or No: 
Yes
Points: 
2
Confidence Level: 
Very High
Answer / Justification: 
The species has "become invasive in other parts of Australia (Victoria, New South Wales), in New Zealand, South Africa, Spain, Portugal and Brazil." (Global Invasive Species Database) Several published scientific papers list the species as invasive. (Marchant et al. 2008, Rodríguez-Echeverría et al. 2009)
Reference(s): 
4. Is the species (or cultivar or variety) noted as being invasive in the US or world in a similar climate?
Yes or No: 
Yes
Points: 
3
Confidence Level: 
Very High
Answer / Justification: 
The species has "become invasive in other parts of Australia (Victoria, New South Wales), in New Zealand, South Africa, Spain, Portugal and Brazil." Areas in Australia (New South Wales), South Africa, Spain and Portugal are similar in climate to the focal area. (Global Invasive Species Database) Several published scientific papers list the species as invasive in the Mediterranean in areas that are similar in climate. (Marchant et al. 2008, Rodríguez-Echeverría et al. 2009)
Reference(s): 
5. Are other species of the same genus (or closely related genera) invasive in a similar climate?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
Very High
Answer / Justification: 
Acacia paradoxica is on the California noxious weed list (CDFA) 3 other Acacias are on the California Invasive Plant Council Inventory as of this writing (January 2020) (Cal-IPC, 2020)
6. Is the species (or cultivar or variety) found predominately in a climate matching the region of concern?
Yes or No: 
Yes
Points: 
2
Confidence Level: 
Medium
Answer / Justification: 
The following areas where the species occurs are similar to the climate of the focal area (California, USA) and make up more than 50% of the range: USA (California), South Africa, Southern Europe (Spain, Portugal, southern France, Italy), most of the Southeastern Australia (native range), central Australia, Western Australia (disjunct from native range), a small area in central Japan. (GBIF) The following areas where the species has naturalized are dissimilar in climate: New Zealand (North Island), South America (east coast of Argentina, Uruguay, Colombia),
Reference(s): 
Impact on Native Plants and Animals
7. Does this plant displace native plants and dominate (overtop or smother) the plant community in areas where it has established?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
High
Answer / Justification: 
Noted as one of the most aggressive invasive species in dunes in Portugal, causing significant ecological impacts (Marchante et al. 2008). The species was also noted changing the native species composition in Portugal, shading out native species (Marchante et al. 2003).
Reference(s): 
8. Is the plant noted as promoting fire and/or changing fire regimes?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
Medium
Answer / Justification: 
Noted as being invasive and "often associated to fire events" in Portugal (Marchante et al. 2008). The seeds are stimulated by fire (Marchante et al. 2003). "In terms of changes in fire regimes, the presence of A. longifolia (especially thickets) increases the risk and intensity of fires." (Global Invasive Species Database)
Reference(s): 
9. Is the plant a health risk to humans or animals/fish? Has the species been noted as impacting grazing systems?
Yes or No: 
No
Points: 
0
Confidence Level: 
High
Answer / Justification: 
Toxicity listed as none [USDA Plants Conservation Plant Characteristics]. No significant information found on the FDA poisonous plants database. Not listed in the Canadian Poisonous Plants Information System - Canadian Biodiversity Information Facility (CBIF).
Reference(s): 
10. Does the plant produce impenetrable thickets, blocking or slowing movement of animals, livestock, or humans?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
High
Answer / Justification: 
Plants grow fairly wide (San Marcos Growers). The species is noted to form thickets, growing wide on many stems (Global Invasive Species Database).
Reference(s): 
Reproductive Strategies
11. Does this species (or cultivar or variety) reproduce and spread vegetatively?
Yes or No: 
No
Points: 
0
Confidence Level: 
Medium
Answer / Justification: 
No mention of reproducing vegetatively despite a lot of information about formation of thickets. All sources indicate reproduction by seed.
Reference(s): 
12. If naturally detached fragments from this plant are capable of producing new plants, is this a common method of reproduction for the plant?
Yes or No: 
No
Points: 
0
Confidence Level: 
Low
Answer / Justification: 
No information found to indicate this. The species could fragment, but it is not documented as a common reproductive method.
Reference(s): 
13. Does the species (or cultivar or variety) commonly produce viable seed?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
Very High
Answer / Justification: 
Indicated that the species may be propagated by seed [USDA Plants Conservation Plant Characteristics] Kew indicates that 50 year old seed is 12% viable [Kew Seed Information Database]
Reference(s): 
14. Does this plant produce copious viable seeds each year (> 1000)?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
High
Answer / Justification: 
Fruit/seed listed as copious (USDA Plants Conservation Plant Characteristics) "Acacia longifolia produces large quantities of seeds annually (up to 11,500 per tree), which are thought to be viable for 50 years. In Portugal often more than 90% of the seeds are viable (E. Marchante, pers. comm.)." (Global Invasive Species Database). "Acacia longifolia plants in long‐invaded and recently invaded areas produced similar amounts of seeds (average under the canopy, 12000 seeds · m–2) each season..." (Marchante et al. 2010)
Reference(s): 
15. Is there significant germination (>25%) of seeds the next growing season, with no requirement of an infrequent environmental condition for seeds to germinate (i.e. fire) or long dormancy period?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
Medium
Answer / Justification: 
Some informal information indicating very high germination in the field in Portugal. (GISD) Some research indicating high viability (95%), but some dormancy. This research also indicates that the species is fire sensitive as opposed to requiring fire (Auld & O'Connell 1991).
Reference(s): 
16. Does this plant produce viable seed within the first three years (for an herbaceous species) to five years (for a woody species) after germination?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
Medium
Answer / Justification: 
The trees reach sexual maturity at 2-3 years. (Global Invasive Species Database)
Reference(s): 
17. Does this plant continuously produce seed for >3 months each year or does seed production occur more than once a year?
Yes or No: 
No
Points: 
0
Confidence Level: 
High
Answer / Justification: 
Calflora lists flowering for 3 months in the summer. [Calflora]
Reference(s): 
Dispersal
18. Are the plant’s propagules frequently dispersed long distance (>100 m) by mammals or birds or via domestic animals?
Yes or No: 
No
Points: 
0
Confidence Level: 
Medium
Answer / Justification: 
Published study of the species in Portugal indicates that the seed has a hard seed coat, ants may disperse the seeds only short distances and that most seeds fall within a short distance of the parent plant.
Reference(s): 
19. Are the plant’s propagules frequently dispersed long distance (>100 m) by wind or water?
Yes or No: 
No
Points: 
0
Confidence Level: 
Medium
Answer / Justification: 
No adaptation for this type of dispersal listed. In fact, published literature indicates the formation of a very dense, localized and persistent seed bank by the hard-coated seeds.
Reference(s): 
20. Are the plant’s propagules frequently dispersed via contaminated seed (agriculture or wildflower packets), equipment, vehicles, boats or clothing/shoes?
Yes or No: 
No
Points: 
0
Confidence Level: 
Low
Answer / Justification: 
No evidence of special mechanism for dispersal this way. Not commonly a contaminant.
Reference(s): 
Evaluation Notes
Notes: 
Total PRE Score

  • < 13 : Low Potential Risk
  • 13 - 15 : Moderate Potential Risk
  • > 15 : High Potential Risk

PRE Score: 
18
Number of questions answered: 
20
Screener Confidence (%): 
75.0
PRE Content Access and Privacy
Evaluation visibility: 
Private - accessible only to organization members

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