Acacia baileyana Risk – California Invasive Plant Council

Created by: Ramona Robison
Created on: Wednesday, Jun 1st, 2016

Evaluation Summary

Summary:

General Evaluation Information

Date of Evaluation:

June 1, 2016

Evaluation Time (hrs):

2 Hours

Evaluation Status:

Completed

Plant Information

Plant:

Acacia baileyana

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

Does this plant grow in the wild in the region under consideration?:

Yes

Is this plant currently being sold in region under consideration?:

Yes

Is this plant on any invasive species list in region under consideration?:

Has any Weed Risk Assessment (WRA) been conducted on this plant for region in question?:

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:

Very High

Answer / Justification:

Naturalized in California. Present in 18 counties according to Calflora. Native of Australia but widely introduced and naturalized in tropical and subtropical regions of the world. There are many points in GBIF.

Reference(s):

Jepson Flora Project (2014). Jepson eFlora.

Calflora (2015). Calflora.

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

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:

Very High

Answer / Justification:

Naturalized in California. Present in 18 counties according to Calflora. There are many points in GBIF, including areas of South Africa, New Zealand and Europe that are similar to California.

Reference(s):

Jepson Flora Project (2014). Jepson eFlora.

Calflora (2015). Calflora.

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

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

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:

Very High

Answer / Justification:

Invasive in South Africa. In South Africa, "Bailey’s wattle competes with indigenous species in forested area and along river banks, and has the potential to replace these species." In Australia outside its native range "it has become a weed of open woodlands, heathlands, grasslands, forest plantations, roadsides, disturbed sites, waste areas and watercourses (i.e. riparian vegetation) in the temperate and sub-tropical regions of Australia."

Reference(s):

[Anonymous] (2012). Invasive Species South Africa.

Castro-Díez, P.., Langendoen T.., Poorter L.., & Saldaña-López A.. (2011). Predicting Acacia invasive success in South Africa on the basis of functional traits, native climatic niche and human use. Biodiversity and Conservation. 20(12),

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

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:

Very High

Answer / Justification:

In South Africa, invades forested areas and along river banks. A regulated weed in South Africa and a problem in Western Cape, Eastern Cape, KwaZulu-Natal, Free State, Mpumalanga and Gauteng.

Reference(s):

[Anonymous] (2012). Invasive Species South Africa.

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

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

Yes or No:

Yes

Points:

Confidence Level:

Very High

Answer / Justification:

There are many species of Acacia listed in Randall 2012. Some are also invasive in California, including A. dealbata and A. melanoxylon.

Reference(s):

Randall, R. (2012). A Global Compendium of Weeds. 2nd Edition..

Calflora (2015). Calflora.

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:

Based on locations in GBIF, it occurs in areas of South Africa, New Zealand and Europe that are similar to California. Map: http://www.gbif.org/species/2981303. According to Donaldson, et al. (2014) A. baileyana may also be able to occupy locations with climates which do not match its native range climate.

Reference(s):

Donaldson, J. E., Chang H.., Richardson D. M., Webber B.L.., & Wilson J.. R. U. (2014). Invasion trajectory of alien trees: the role of introduction pathway and planting history. Global Change Biology. 20(5), 1527-1537.

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

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

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:

High

Answer / Justification:

In South Africa, "Bailey’s wattle competes with indigenous species in forested area and along river banks, and has the potential to replace these species." In Australia A. baileyana can displace other wattles (Acacia spp.) that are native to a particular area, and can also form dense stands that shade out other native plants.

Reference(s):

[Anonymous] (2012). Invasive Species South Africa.

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

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

Yes or No:

Yes

Points:

Confidence Level:

High

Answer / Justification:

In fynbos they [invasive Acacias] change plant community structure and increase flammability through increased fuel loads. In fynbos they also increase soil erosion due to water repellancy induced by very intense fires in dense stands (Richardson and Kluge 2008). "Acacias often tend to become dominant species after fire and it is usually assumed that the heat of the fire softens or cracks the seed coat, thus permitting germination if suitable rains fall (Cananagh 1980)."

Reference(s):

Cananagh, A.K.. (1980). A REVIEW OF SOME ASPECTS OF THE GERMINATION OF ACACIAS. Proceedings of the Royal Society of Victoria. 91(1-2), 161–180.

Richardson, D. M., & Kluge R. L. (2008). Seed banks of invasive Australian Acacia species in South Africa: Role in invasiveness and options for management. Perspectives in Plant Ecology, Evolution and Systematics. 10(3), 161–177.

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

Yes or No:

Points:

Confidence Level:

Medium

Answer / Justification:

No mention of toxicity in references. Pods are grazed on by African mammals and seedlings have been found in the dung of impalas, elephants, dik-diks, and gazelles, and in goat dung in abandoned goat enclosures (Cananagh 1980). When grazing was removed in Australia, Acacia plants recovered.

Reference(s):

Cananagh, A.K.. (1980). A REVIEW OF SOME ASPECTS OF THE GERMINATION OF ACACIAS. Proceedings of the Royal Society of Victoria. 91(1-2), 161–180.

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

Yes or No:

Yes

Points:

Confidence Level:

Medium

Answer / Justification:

Dense stands of acacias, mainly A. cyclops and A. saligna, form impenetrable stands over thousands of hectares in lowlands of the fynbos biome (Richardson and Kluge 2008).

Reference(s):

Reproductive Strategies

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

Yes or No:

Points:

Confidence Level:

Medium

Answer / Justification:

Mostly propagated by seed, but can be propagated from semi-hardwood cuttings (Dave's Garden)

Reference(s):

Dave's Garden (2015). Dave's Garden.

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:

Answer / Justification:

Mostly propagated by seed, but can be propagated from semi-hardwood cuttings (Dave's Garden)

Reference(s):

Dave's Garden (2015). Dave's Garden.

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

Yes or No:

Yes

Points:

Confidence Level:

Very High

Answer / Justification:

Maximum flower production for a 2-year-old plant was over 300,000, resulting in more than 8,000 seeds (Morgan 2002).

Reference(s):

Morgan, A., Carthew S. M., & Sedgley M. (2002). Breeding system, reproductive efficiency and weed potential of A. baileyana. Australian Jounal of Botany. 50(3), 357–364.

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

Yes or No:

Yes

Points:

Confidence Level:

Very High

Answer / Justification:

In Australia, for populations naturalized from horticultural escapes, "both forms [studied] were outcrossing, highly self-incompatible, grew very rapidly and flowered by two years of age. For open, natural pollination, final pod set was low-less than 0.41%. However, seed production was high due to the high number of flowers present. Maximum flower production for a 2-year-old plant was over 300,000, resulting in more than 8,000 seeds (Morgan 2002a). In another study Morgan (2002b) used digital imagery to estimate seed production per tree. They found that "Average pod set for the 10 trees was 0.12%, and average seeds per pod was 4.0. Nevertheless, because of the large number of flowers, the average seed production was over 19,500."

Reference(s):

Morgan, A., Carthew S. M., & Sedgley M. (2002). Breeding system, reproductive efficiency and weed potential of A. baileyana. Australian Jounal of Botany. 50(3), 357–364.

Morgan, A. (2002). Using digital image analysis to estimate flower numbers of Cootamundra wattle (Acacia baileyana F. Muell.) and hence determine seed production and weed potential.. (Adams, P., Kolesik P., Sedgley M., Carthew S., & Haskard K., Ed.).Plant Protection Quarterly. 17(4), 162–167.

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:

Confidence Level:

High

Answer / Justification:

Seed bank dynamics are discussed in Richardson and Kluge (2008). A. baileyana is in a group of Acacias with seed banks characterized as "persistent." A small proportion of the seeds germinate or decay within the first three months and the majority persist thereafter. Seed turnover is slow and there is rapid accumulation.

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:

Very High

Answer / Justification:

Reference(s):

Morgan, A., Carthew S. M., & Sedgley M. (2002). Breeding system, reproductive efficiency and weed potential of A. baileyana. Australian Jounal of Botany. 50(3), 357–364.

17. Does this plant produce seed for >3 months each year or does seed production occur more than once a year?

Yes or No:

Yes

Points:

Confidence Level:

High

Answer / Justification:

A. baileyana has a flowering length of 4 months in Africa (Castro-Diez 2011) and 3 months in New Zealand (Wandrag 2015). In California it is reported to flower for 3 months a year (Calflora).

Reference(s):

Wandrag, E.. M., Sheppard A.. W., Duncan R.. P., & Hulme P.. E. (2015). Pollinators and predators at home and away: do they determine invasion success for Australian Acacia in New Zealand?. (W. Kissling, D., Ed.).Journal of Biogeography. 42, 619–629.

Calflora (2015). Calflora.

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:

Seeds can be dispersed in animal dung. Pods are grazed on by African mammals and seedlings have been found in the dung of impalas, elephants, dik-diks, and gazelles, and in goat dung in abandoned goat enclosures (Cananagh 1980).

Reference(s):

Cananagh, A.K.. (1980). A REVIEW OF SOME ASPECTS OF THE GERMINATION OF ACACIAS. Proceedings of the Royal Society of Victoria. 91(1-2), 161–180.

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:

Seeds may be dispersed short distances when the pods split open explosively in hot weather, and by ants that collect the seeds and take them to their nests. The relatively light and papery pods may also be spread some distance by wind and water (Queensland Government).

Reference(s):

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

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:

Medium

Answer / Justification:

As this species is commonly cultivated, one of the main means of dispersal is in dumped garden waste. Longer distance dispersal can also occur when contaminated soil or mud is transported by vehicles (Queensland Government).

Reference(s):

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

Evaluation Notes

South Africa: http://www.invasives.org.za/component/k2/item/193-bailey-s-wattle

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

Reviewed by Barbara Castro.

Total PRE Score