Onopordum illyricum Risk – California Invasive Plant Council

Created by: Ramona Robison
Created on: Monday, Aug 8th, 2016

Evaluation Summary

Summary:

General Evaluation Information

Date of Evaluation:

August 8, 2016

Evaluation Time (hrs):

3 Hours

Evaluation Status:

Completed

Plant Information

Plant:

Onopordum illyricum

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:

California

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.

Link to Climate Matching Map:

Climate Matching Maps PDF:

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:

Confidence Level:

High

Answer / Justification:

Naturalized in California. Present in 2 counties according to Calflora. Also naturalized in Australia.

Reference(s):

Calflora (2015). Calflora.

GBIF (0). Global Biodiversity Information Facility (GBIF).

Queensland Government (2011). Weeds of Australia Biosecurity Queensland Edition.

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:

Confidence Level:

High

Answer / Justification:

Naturalized in California. Present in 2 counties according to Calflora. Also naturalized in Australia in areas which match California's climate.

Reference(s):

Calflora (2015). Calflora.

GBIF (0). Global Biodiversity Information Facility (GBIF).

-IPC, C. (2016). Cal-IPC global map of climate areas matching California.

3. Is the species (or cultivar or variety) noted as being invasive in the U.S. or world?

Yes or No:

Yes

Points:

Confidence Level:

High

Answer / Justification:

Considered invasive in Australia, details included in an Invasiveness Assessment and Impact Assessment prepared by the Victoria State Government.

Reference(s):

Department of Environment, Victoria Primary Industries (2015). Agriculture Victoria (VRO).

Victoria Dept. of Environment and Primary Industries (2015). Victorian Invasive Plants.

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:

Confidence Level:

High

Answer / Justification:

Considered invasive in Australia, details included in an Invasiveness Assessment and Impact Assessment prepared by the Victoria State Government. Is present in New South Wales in areas with climates which match California.

Reference(s):

Department of Environment, Victoria Primary Industries (2015). Agriculture Victoria (VRO).

Victoria Dept. of Environment and Primary Industries (2015). Victorian Invasive Plants.

-IPC, C. (2016). Cal-IPC global map of climate areas matching California.

GBIF (0). Global Biodiversity Information Facility (GBIF).

5. Are other species of the same genus (or closely related genera) invasive in a similar climate?

Yes or No:

Yes

Points:

Confidence Level:

High

Answer / Justification:

Onopordum acanthium is also considered invasive in Australia in areas which match California's climate.

Reference(s):

GBIF (0). Global Biodiversity Information Facility (GBIF).

-IPC, C. (2016). Cal-IPC global map of climate areas matching California.

Queensland Government (2011). Weeds of Australia Biosecurity Queensland Edition.

6. Is the species (or cultivar or variety) found predominately in a climate matching the region of concern?

Yes or No:

Yes

Points:

Confidence Level:

High

Answer / Justification:

O. illyricum points in GBIF for its native distribution in southern Europe as well as some of the points for Australia match California's climate.

Reference(s):

-IPC, C. (2016). Cal-IPC global map of climate areas matching California.

GBIF (0). Global Biodiversity Information Facility (GBIF).

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:

Confidence Level:

Medium

Answer / Justification:

“Even when plants die, they usually remain standing for a long period of time and, by keeping the area bare of other vegetation, can maintain a niche for recruitment of the next generation.”

Reference(s):

Victoria Dept. of Environment and Primary Industries (2015). Victorian Invasive Plants.

8. Is the plant noted as promoting fire and/or changing fire regimes?

Yes or No:

Yes

Points:

Confidence Level:

Medium

Answer / Justification:

Stems can persist into the next season with spiny phyllaries and receptacles attached. In dense patches, this dry matter may introduce a minor change to the frequency of fire risk.

Reference(s):

Victoria Dept. of Environment and Primary Industries (2015). Victorian Invasive Plants.

9. Is the plant a health risk to humans or animals/fish? Has the species been noted as impacting grazing systems?

Yes or No:

Yes

Points:

Confidence Level:

Medium

Answer / Justification:

O. illyricum impacts grazing systems because it is spiny. Illyrian thistle tends not to be grazed by stock because of its dense spines. However, if the weed is grazed, the spines can cause damage, particularly around the mouths and eyes of animals.

Reference(s):

Department of Environment, Victoria Primary Industries (2015). Agriculture Victoria (VRO).

10. Does the plant produce impenetrable thickets, blocking or slowing movement of animals, livestock, or humans?

Yes or No:

Yes

Points:

Confidence Level:

High

Answer / Justification:

“Dense patches pose a physical barrier to humans.” The spiny nature of the plant is an annoyance to humans.

Reference(s):

Victoria Dept. of Environment and Primary Industries (2015). Victorian Invasive Plants.

Reproductive Strategies

11. Does this species (or cultivar or variety) reproduce and spread vegetatively?

Yes or No:

Points:

Confidence Level:

High

Answer / Justification:

Illyrian thistle's only method of dispersal is by seed which is equipped with a pappus of fine hairs and is spread by both wind and water.

Reference(s):

Department of Environment, Victoria Primary Industries (2015). Agriculture Victoria (VRO).

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:

Points:

Confidence Level:

High

Answer / Justification:

Illyrian thistle's only method of dispersal is by seed which is equipped with a pappus of fine hairs and is spread by both wind and water.

Reference(s):

Department of Environment, Victoria Primary Industries (2015). Agriculture Victoria (VRO).

13. Does the species (or cultivar or variety) commonly produce viable seed?

Yes or No:

Yes

Points:

Confidence Level:

High

Answer / Justification:

Illyrian thistle's only method of dispersal is by seed which is equipped with a pappus of fine hairs and is spread by both wind and water.

Reference(s):

Department of Environment, Victoria Primary Industries (2015). Agriculture Victoria (VRO).

Rees, M.., Sheppard A.., Briese D.., & Mangel M.. (1999). Evolution of size-dependent flowering in Onopordum illyricum: A quantitative assessment of the role of stochastic selection pressures. American Naturalist. 154, 628–651.

14. Does this plant produce copious viable seeds each year (> 1000)?

Yes or No:

Yes

Points:

Confidence Level:

Medium

Answer / Justification:

“A heavy seeder” 5 flower heads per plant x 200 seeds per flower = 1,000 seeds per plant (Estimate using pic. & illustrations)

Reference(s):

Victoria Dept. of Environment and Primary Industries (2015). Victorian Invasive Plants.

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:

Points:

Confidence Level:

High

Answer / Justification:

Illyrian thistle seeds have an initial short-term innate dormancy, following which the majority of seeds acquire induced dormancy, rendering them incapable of immediate germination.

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:

Confidence Level:

High

Answer / Justification:

Some O. illyricum plants flower in the first year, others in the second year.

Reference(s):

Victoria Dept. of Environment and Primary Industries (2015). Victorian Invasive Plants.

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:

Points:

Confidence Level:

Medium

Answer / Justification:

In Austraila, Illyrian thistle flowers for three months and produces seed for 3 months.

Reference(s):

Department of Environment, Victoria Primary Industries (2015). Agriculture Victoria (VRO).

Dispersal

18. Are the plant’s propagules frequently dispersed long distance (>100 m) by mammals or birds or via domestic animals?

Yes or No:

Yes

Points:

Confidence Level:

High

Answer / Justification:

The pappus of the seed attaches to wool, vehicles, clothing, etc. or it can be a contaminant in hay.

Reference(s):

Victoria Dept. of Environment and Primary Industries (2015). Victorian Invasive Plants.

19. Are the plant’s propagules frequently dispersed long distance (>100 m) by wind or water?

Yes or No:

Yes

Points:

Confidence Level:

High

Answer / Justification:

Illyrian thistle's only method of dispersal is by seed which is equipped with a pappus of fine hairs and is spread by both wind and water.

Reference(s):

Department of Environment, Victoria Primary Industries (2015). Agriculture Victoria (VRO).

20. Are the plant’s propagules frequently dispersed via contaminated seed (agriculture or wildflower packets), equipment, vehicles, boats or clothing/shoes?

Yes or No:

Yes

Points:

Confidence Level:

High

Answer / Justification:

The pappus of the seed attaches to wool, vehicles, clothing, etc or it can be a contaminant in hay.

Reference(s):

Victoria Dept. of Environment and Primary Industries (2015). Victorian Invasive Plants.

Evaluation Notes

Queensland Government: http://keyserver.lucidcentral.org/weeds/data/media/Html/onopordum_acanth...

GBIF: http://www.gbif.org/species/3094910