Plant Assessment Form
More Carduus pycnocephalus resources
Carduus pycnocephalus
Common Names: Italian thistle
Evaluated on: 5/22/04
List committee review date: 08/07/2005
Re-evaluation date:
Evaluator(s)
John J. Knapp/ Invasive Plant Program Manager
Catalina Island Conservancy
P.O. Box 2739 Avalon, CA 90704
(310) 510-1299
jknapp@catalinaconservancy.org
Joseph DiTomaso
University of California-Davis
Dept. Plant Sci., Mail Stop 4, Davis, CA 95616
530-754-8715
jmditomaso@ucdavis.edu
List committee members
Carla Bossard
John Randall
Carri Pirosko
Dan Gluesenkamp
Gina Skurka
Brianna Richardson
General Comments
No general comments for this species
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|
Overall Score ?
Plant scoring matrix
Based on letter scores from Sections 1 through 3 below
| Impact | Invasiveness | Distribution | | |
| A | A B | Any | High | No Alert |
| A | C D | Any | Moderate | Alert |
| B | A B | A B | Moderate | No Alert |
| B | A B | C D | Moderate | Alert |
| B | C D | Any | Limited | No Alert |
| C | A | A B | Moderate | No Alert |
| C | A | C D | Limited | No Alert |
| C | B | A | Moderate | No Alert |
| C | B | B D | Limited | No Alert |
| C | C | Any | Limited | No Alert |
| D | Any | Any | Not Listed | No Alert |
Moderate
|
Alert Status ?
Plant scoring matrix
Based on letter scores from Sections 1 through 3 below
| Impact | Invasiveness | Distribution | Alert |
| A | A or B | C or D | Alert |
| B | A or B | C or D | Alert |
No Alert
|
Documentation ?
The total documentation score is the average
of Documentation scores given in Table 2.
| Reviewed Scientific Publication | 4 points |
| Other Published Material | 3 points |
| Observational | 2 points |
| Anecdotal | 1 points |
| Unknown or No Information | 0 points |
3 out of 5 |
|
|
Score |
Documentation |
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| 1.1 |
?Impact on abiotic ecosystem processes
Consider the impact on the natural range and variation of abiotic ecosystem processes and system-wide parameters in ways that significantly diminish the ability of native species to survive and reproduce. Alterations that determine the types of communities that can exist in a given area are of greatest concern. Examples of abiotic processes include:
- fire occurrence, frequency, and intensity;
- geomorphological changes such as erosion and sedimentation rates;
- hydrological regimes, including soil water table;
- nutrient and mineral dynamics, including salinity, alkalinity, and pH;
- light availability (e.g. when an aquatic invader covers an entire water body that would otherwise be open).
Select the one letter below that best describes this species' most severe impact on an abiotic ecosystem process:
A. Severe, possibly irreversible, alteration or disruption of an ecosystem process.
B. Moderate alteration of an ecosystem process.
C. Minor alteration of an ecosystem process.
D. Negligible perceived impact on an ecosystem process.
U. Unknown.
|
C. Minor |
Other Published Material |
Impact?
| Section 1 Scoring Matrix |
|---|
| Q 1.1 | Q 1.2 | Q 1.3 | Q 1.4 | Score |
| A | A | Any | Any | A |
| A | B | A,B | Any | A |
| A | B | C,D,U | Any | B |
| A | C,D,U | Any | Any | B |
| B | A | A | Any | A |
| B | A | B | A | A |
| B | A | B,C | B-D,U | B |
| B | A | C,D,U | A | A |
| B | A | C,D,U | B-D,U | B |
| B | B | A | A | A |
| B | C,D,U | A | A | B |
| B | B-D | A | B-D,U | B |
| B | B-D | B-D,U | Any | B |
| B | D,U | C,D,U | A-B | B |
| B | D,U | C,D,U | C,D,U | C |
| C-D,U | A | A | Any | A |
| C | B | A | Any | B |
| C | A,B | B-D,U | Any | B |
| C | C,D,U | Any | Any | C |
| D | A,B | B | Any | B |
| D | A,B | C,D,U | Any | C |
| D | C | Any | Any | C |
| D | D,U | Any | Any | D |
| U | A | B,C | Any | B |
| U | B,C | A,B | Any | B |
| U | B,C | C,D,U | Any | C |
| U | U | Any | Any | U |
Four-part score
CABD
Total Score
B
|
| 1.2 |
?Impact on plant community
Consider the cumulative ecological impact of this species to the plant communities it invades. Give more weight to changes in plant composition, structure, and interactions that involve rare or keystone species or rare community types. Examples of severe impacts include:
- formation of stands dominated (>75% cover) by the species;
- occlusion (>75% cover) of a native canopy, including a water surface, that eliminates or degrades layers below;
- significant reduction or extirpation of populations of one or more native species.
Examples of impacts usually less than severe include:
- reduction in propagule dispersal, seedling recruitment, or survivorship of native species;
- creation of a new structural layer, including substantial thatch or litter, without elimination or replacement of a pre-existing layer;
- change in density or depth of a structural layer;
- change in horizontal distribution patterns or fragmentation of a native community;
- creation of a vector or intermediate host of pests or pathogens that infect native plant species.
Select the one letter below that best describes this species' impact on community composition, structure and interactions:
A. Severe alteration of plant community composition, structure, or interactions.
B. Moderate alteration of plant community composition.
C. Minor alteration of community composition.
D. Negligible impact known; causes no perceivable change in community composition, structure, or interactions.
U. Unknown.
|
A. Severe |
Other Published Material |
| 1.3 |
?Impact on higher trophic levels
Consider the cumulative impact of this species on the animals, fungi, microbes, and other organisms in the communities that it invades. Although a non-native species may provide resources for one or a few native species (e.g. by providing food, nesting sites, etc.), the ranking should be based on the species' net impact on all native species. Give more weight to changes in composition and interactions involving rare or keystone species or rare community types.
Examples of severe impacts include:
- extirpation or endangerment of an existing native species or population;
- elimination or significant reduction in native species' nesting or foraging sites, cover, or other critical resources (i.e., native species habitat), including migratory corridors.
Examples of impacts that are usually less than severe include:
- minor reduction in nesting or foraging sites, cover, etc. for native animals;
- minor reduction in habitat connectivity or migratory corridors;
- interference with native pollinators;
- injurious components, such as awns or spines that damage the mouth and gut of native wildlife species, or production of anti-digestive or acutely toxic chemical that can poison native wildlife species.
Select the one letter below that best describes this species' impact on community composition and interactions:
A. Severe alteration of higher trophic populations, communities, or interactions.
B. Moderate alteration of higher trophic level populations, communities, or interactions.
C. Minor alteration of higher trophic level populations, communities or interactions.
D. Negligible impact; causes no perceivable change in higher trophic level populations, communities, or interactions.
E. Unknown.
|
B. Moderate |
Other Published Material |
| 1.4 |
?Impact on genetic integrity
Consider whether the species can hybridize with and influence the proportion of individuals with non-native genes within populations of native species. Mechanisms and possible outcomes include:
- production of fertile or sterile hybrids that can outcompete the native species;
- production of sterile hybrids that lower the reproductive output of the native species.
Select the one letter below that best describes this species' impact on genetic integrity:
A. Severe (high proportion of individuals).
B. Moderate (medium proportion of individuals).
C. Minor (low proportion of individuals).
D. No known hybridization.
U. Unknown.
|
D. None |
Other Published Material |
|
| 2.1 |
?Role of anthropogenic and natural disturbance in establishment
Assess dependence on disturbance, both human and natural, for establishment of this species in wildlands. Examples of anthropogenic disturbances include:
- grazing, browsing, and rooting by domestic livestock and feral animals;
- altered fire regimes, including fire suppression;
- cultivation;
- silvicultural practices;
- altered hydrology due to dams, diversions, irrigation, etc.;
- roads and trails;
- construction;
- nutrient loading from fertilizers, runoff, etc.
Examples of natural disturbance include:
- wildfire;
- floods;
- landslides;
- windthrow;
- native animal activities such as burrowing, grazing, or browsing.
Select the first letter in the sequence below that describes the ability of this species to invade wildlands:
A. Severe invasive potential: this species can establish independent of any known natural or anthropogenic disturbance.
B. Moderate invasive potential: this species may occasionally establish in undisturbed areas but can readily establish in areas with natural disturbances.
C. Low invasive potential: this species requires anthropogenic disturbance to establish.
D. No perceptible invasive potential: this species does not establish in wildlands (though it may persist from former cultivation).
U. Unknown.
|
B. Moderate |
Other Published Material |
Invasiveness?
| Section 2 Scoring Matrix |
| Total points | Score |
| 17-21 | A |
| 11-16 | B |
| 5-10 | C |
| 0-4 | D |
| More than two U's | U |
Total Points
12
Total Score
B
|
| 2.2 |
?Local rate of spread with no management
Assess rate of spread in existing localized infestations where the proportion of available habitat invaded is still small when no management measures are implemented.
Select the one letter below that best describes the rate of spread:
A. Increases rapidly (doubling in <10 years)
B. Increases, but less rapidly
C. Stable
D. Declining
U. Unknown
|
B. Increases less rapidly |
Other Published Material |
| 2.3 |
?Recent trend in total area infested within state
Assess the overall trend in the total area infested by this species statewide. Include current management efforts in this assessment and note them.
Select the one letter below that best describes the current trend:
A. Increasing rapidly (doubling in total range statewide in <10 years)
B. Increasing, but less rapidly
C. Stable
D. Declining
U. Unknown
|
B. Increasing less rapidly |
Other Published Material |
| 2.4 |
?Innate reproductive potential
(see Worksheet A)
Assess the innate reproductive potential of this species. Worksheet A is provided for computing the score.
|
B. Moderate |
Other Published Material |
| 2.5 |
?Potential for human-caused dispersal
Assess whether this species is currently spread: or has high potential to be spread: by direct or indirect human activity. Such activity may enable the species to overcome natural barriers to dispersal that would not be crossed otherwise, or it may simply increase the natural dispersal of the species. Possible mechanisms for dispersal include:
- commercial sales for use in agriculture, ornamental horticulture, or aquariums;
- use as forage, erosion control, or revegetation;
- presence as a contaminant (seeds or propagules) in bulk seed, hay, feed, soil, packing materials, etc.;
- spread along transportation corridors such as highways, railroads, trails, or canals;
- transport on boats or boat trailers.
Select the one letter below that best describes human-caused dispersal and spread:
A. High: there are numerous opportunities for dispersal to new areas.
B. Moderate: human dispersal occurs, but not at a high level.
C. Low: human dispersal is infrequent or inefficient.
D. Does not occur.
U. Unknown.
|
B. Moderate |
Other Published Material |
| 2.6 |
? Potential for natural long-distance dispersal
We have chosen 1 km as the threshold of "long-distance." Assess whether this species is frequently spread, or has high potential to be spread, by animals or abiotic mechanisms that can move seed, roots, stems, or other propagules this far. The following are examples of such natural long-distance dispersal mechanisms:
- the species' fruit or seed is commonly consumed by birds or other animals that travel long distances;
- the species' fruits or seeds are sticky or burred and cling to feathers or hair of animals;
- the species has buoyant fruits, seeds, or other propagules that are dispersed by flowing water;
- the species has light propagules that promote long-distance wind dispersal;
- The species, or parts of it, can detach and disperse seeds as they are blown long distances (e.g., tumbleweed).
Select the one letter below that best describes natural long-distance dispersal and spread:
A. Frequent long-distance dispersal by animals or abiotic mechanisms.
B. Occasional long-distance dispersal by animals or abiotic mechanisms.
C. Rare dispersal more than 1 km by animals or abiotic mechanisms.
D. No dispersal of more than 1 km by animals or abiotic mechanisms.
U. Unknown.
|
C. Rare |
Other Published Material |
| 2.7 |
?Other regions invaded
Assess whether this species has invaded ecological types in other states or countries outside its native range that are analogous to ecological types not yet invaded in your state (see Worksheets B, C, and D for California, Arizona, and Nevada, respectively, in Part IV for lists of ecological types). This information is useful in predicting the likelihood of further spread within your state.
Select the one letter below that best describes the species' invasiveness in other states or countries, outside its native range.
A. This species has invaded 3 or more ecological types elsewhere that exist in your state and are as yet not invaded by this species (e.g. it has invaded Mediterranean grasslands, savanna, and maquis in southern Europe, which are analogous to California grasslands, savanna, and chaparral, respectively).
B. Invades 1 or 2 ecological types that exist but are not yet invaded in your state.
C. Invades elsewhere but only in ecological types that it has already invaded in the state.
D. Not known as an escape anywhere else.
U. Unknown.
|
C. Already invaded |
Other Published Material |
|
| 3.1 |
?Ecological amplitude/Range
(see Worksheet C)
Refer to Worksheet C and select the one letter below that indicates the number of different ecological types that this species invades.
A. Widespread: the species invades at least three major types or at least six minor types.
B. Moderate: the species invades two major types or five minor types.
C. Limited: the species invades only one major type and two to four minor types.
D. Narrow: the species invades only one minor type.
U. Unknown.
|
A. Widespread |
Other Published Material |
Distribution?
| Section 3 Scoring Matrix |
| Q 3.1 | Q 3.2 | Score |
| A | A, B | A |
| A | C,D,U | B |
| B | A | A |
| B | B,C | B |
| B | D | C |
| C | A,B | B |
| C | C,D | C |
| D | A | B |
| D | B,C | C |
| D | D | D |
| A,B | U | C |
| C,D | U | D |
| U | U | U |
Total Score
A
|
| 3.2 |
?Distribution/Peak frequency
(see Worksheet C)
To assess distribution, record the letter that corresponds to the highest percent infested score entered in Worksheet C for any ecological type.
|
B. Moderate |
Observational |
Scores are explained in the "Criteria for Categorizing Invasive Non-Native Plants that Threaten Wildlands".
| Section 1: Impact |
Question 1.1 Impact on abiotic ecosystem processes?
Consider the impact on the natural range and variation of abiotic ecosystem processes and system-wide parameters in ways that significantly diminish the ability of native species to survive and reproduce. Alterations that determine the types of communities that can exist in a given area are of greatest concern. Examples of abiotic processes include:
- fire occurrence, frequency, and intensity;
- geomorphological changes such as erosion and sedimentation rates;
- hydrological regimes, including soil water table;
- nutrient and mineral dynamics, including salinity, alkalinity, and pH;
- light availability (e.g. when an aquatic invader covers an entire water body that would otherwise be open).
Select the one letter below that best describes this species' most severe impact on an abiotic ecosystem process:
A. Severe, possibly irreversible, alteration or disruption of an ecosystem process.
B. Moderate alteration of an ecosystem process.
C. Minor alteration of an ecosystem process.
D. Negligible perceived impact on an ecosystem process.
U. Unknown.
|
C
Other Published Material
|
Identify ecosystem processes impacted:
C. pycnocephalus increases fire frequency and movement into overstory of island scrub oak chaparral, and dense populations of rosettes inhibit light penetration to the soil surface. Fire is carried into the oak overstory by C. pycnocephalus midstory. This may or may not increase the threat compared to native vegetation or annual grasses in the same area, but the Italian thistle plants tend to grow taller and be a better fire ladder than other species.
Sources of information:
Wilken, D. and Hannah, L. 1998. Carduus pycnocephalus. Channel Islands National Park Service Species Literature Review. Unpublished.
Anonymous. 2003. Written findings of the State Noxious Weed Control Board-Class A Weed. http://www.nwcb.wa.gov/weed_info/Written_findings/Carduus_pycnocephalus.html
|
Question 1.2 Impact on plant community composition,
structure, and interactions?
Consider the cumulative ecological impact of this species to the plant communities it invades. Give more weight to changes in plant composition, structure, and interactions that involve rare or keystone species or rare community types. Examples of severe impacts include:
- formation of stands dominated (>75% cover) by the species;
- occlusion (>75% cover) of a native canopy, including a water surface, that eliminates or degrades layers below;
- significant reduction or extirpation of populations of one or more native species.
Examples of impacts usually less than severe include:
- reduction in propagule dispersal, seedling recruitment, or survivorship of native species;
- creation of a new structural layer, including substantial thatch or litter, without elimination or replacement of a pre-existing layer;
- change in density or depth of a structural layer;
- change in horizontal distribution patterns or fragmentation of a native community;
- creation of a vector or intermediate host of pests or pathogens that infect native plant species.
Select the one letter below that best describes this species' impact on community composition, structure and interactions:
A. Severe alteration of plant community composition, structure, or interactions.
B. Moderate alteration of plant community composition.
C. Minor alteration of community composition.
D. Negligible impact known; causes no perceivable change in community composition, structure, or interactions.
U. Unknown.
|
A
Other Published Material
|
Identify type of impact or alteration:
Both rosettes and mature adults populations can reach nearly 100% cover over large areas inhibiting seedling recruitment and survivorship. Within island scrub oak chaparral habitat, C. pycnocephalus can form an midstory layer. 85% of seeds produce germination inhibitors, but they are readily leached. Both the depth and density of grasslands are altered. Harbors insect pests.
Host plant for introduced weevil Rhynocilus conicus, which attacks native thistles, thereby reducing populations of the native plants (Gluesenkamp and Randall).
Sources of information:
Wilken, D. and Hannah, L. 1998. Carduus pycnocephalus. Channel Islands National Park Service Species Literature Review. Unpublished.
Knapp, J.J. 2004. Catalina Invasive Plant Ranking Plan for the Catalina Island Conservancy. Unpublished.
Pitcher, D. and Russo, M.J. 1997. The Nature Conservancy Element Stewardship Abstract: Carduus pycnocephalus. California Field Office, San Francisco
Dan Gluesenkamp, Audubon Canyon Ranch, and John Randall, The Nature Conservancy, pers. obs.
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Question 1.3 Impact on higher trophic levels?
Consider the cumulative impact of this species on the animals, fungi, microbes, and other organisms in the communities that it invades. Although a non-native species may provide resources for one or a few native species (e.g. by providing food, nesting sites, etc.), the ranking should be based on the species' net impact on all native species. Give more weight to changes in composition and interactions involving rare or keystone species or rare community types.
Examples of severe impacts include:
- extirpation or endangerment of an existing native species or population;
- elimination or significant reduction in native species' nesting or foraging sites, cover, or other critical resources (i.e., native species habitat), including migratory corridors.
Examples of impacts that are usually less than severe include:
- minor reduction in nesting or foraging sites, cover, etc. for native animals;
- minor reduction in habitat connectivity or migratory corridors;
- interference with native pollinators;
- injurious components, such as awns or spines that damage the mouth and gut of native wildlife species, or production of anti-digestive or acutely toxic chemical that can poison native wildlife species.
Select the one letter below that best describes this species' impact on community composition and interactions:
A. Severe alteration of higher trophic populations, communities, or interactions.
B. Moderate alteration of higher trophic level populations, communities, or interactions.
C. Minor alteration of higher trophic level populations, communities or interactions.
D. Negligible impact; causes no perceivable change in higher trophic level populations, communities, or interactions.
E. Unknown.
|
B
Other Published Material
|
Identify type of impact or alteration:
Stem and leaves have spiny wings and phyllaries that are spine tipped, and may be injurous components to wildlife. Dense populations can alter habitat structure. A diversity of insects pollinate C. pycnocephalus. Competes with native vegetation for multiple pollinator visitation due to numerous seed heads.
Sources of information:
Wilken, D. and Hannah, L. 1998. Carduus pycnocephalus. Channel Islands National Park Service Species Literature Review. Unpublished.
Anonomous. 2003. Written findings of the State Noxious Weed Control Board-Class A Weed. http://www.nwcb.wa.gov/weed_info/Written_findings/Carduus_pycnocephalus.html
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Question 1.4 Impact on genetic integrity?
Consider whether the species can hybridize with and influence the proportion of individuals with non-native genes within populations of native species. Mechanisms and possible outcomes include:
- production of fertile or sterile hybrids that can outcompete the native species;
- production of sterile hybrids that lower the reproductive output of the native species.
Select the one letter below that best describes this species' impact on genetic integrity:
A. Severe (high proportion of individuals).
B. Moderate (medium proportion of individuals).
C. Minor (low proportion of individuals).
D. No known hybridization.
U. Unknown.
|
D
Other Published Material
|
No hybridization is known to occur with California native taxa. No taxa native to California are within the genus Carduus.
Sources of information:
Hickman, J.C. (ed.). 1993. The Jepson manual of higher plants of California. P. 220. University of California Press, Berkeley.
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| Section 2: Invasiveness |
Question 2.1 Role of anthropogenic and natural disturbance
in establishment?
Assess this species' dependence on disturbance: both human and natural: for establishment in wildlands. Examples of anthropogenic disturbances include:
- grazing, browsing, and rooting by domestic livestock and feral animals;
- altered fire regimes, including fire suppression;
- cultivation;
- silvicultural practices;
- altered hydrology due to dams, diversions, irrigation, etc.;
- roads and trails;
- construction;
- nutrient loading from fertilizers, runoff, etc.
Examples of natural disturbance include:
- wildfire;
- floods;
- landslides;
- windthrow;
- native animal activities such as burrowing, grazing, or browsing.
Select the first letter in the sequence below that describes the ability of this species to invade wildlands:
A. Severe invasive potential: this species can establish independent of any known natural or anthropogenic disturbance.
B. Moderate invasive potential: this species may occasionally establish in undisturbed areas but can readily establish in areas with natural disturbances.
C. Low invasive potential: this species requires anthropogenic disturbance to establish.
D. No perceptible invasive potential: this species does not establish in wildlands (though it may persist from former cultivation).
U. Unknown.
|
B
Other Published Material
|
Describe role of disturbance:
Disturbed sites such as: fallow fields, margins of cultivated fields, irrigation canals, roadsides, fire breaks, landsides, feral pig rooting, grazed heavily, and canyon bottoms are areas of establishment.
Sources of information:
Wilken, D. and Hannah, L. 1998. Carduus pycnocephalus. Channel Islands National Park Service Species Literature Review. Unpublished.
Anonomous. 2003. Written findings of the State Noxious Weed Control Board-Class A Weed.
Cowan, B. 2000. Italian thistles: an ominous threat. California Exotic Pest Plant Council News, 8(1):15.
Elkhorn Slough National Estuarine Research Reserve. 2000. Weed control by species. Elkhorn Slough National Estuarine Research Reserve. Pp. 1-57.
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Question 2.2 Local rate of spread with no management?
Assess this species' rate of spread in existing localized infestations where the proportion of available habitat invaded is still small when no management measures are implemented.
Select the one letter below that best describes the rate of spread:
A. Increases rapidly (doubling in <10 years)
B. Increases, but less rapidly
C. Stable
D. Declining
U. Unknown
|
B
Other Published Material
|
Describe rate of spread:
Populations are maintained annually by a majority of seed that fall within a few meters of the population each year. Long distance wind dispersal allows for new satellite populations to form. C. pycnocephalus is described as an aggressive species. Ants are suspected of microdistribution of seed. New populations are being detected each year, and are increasing in size along the Big Sur Coast and Catalina Island. Neither the 1923 or 1967 floras for Catalina Island recorded populations of C. pycnocephalus, but in 2003, 200 population were rcorded throughout the Island. Germinates rapidly in large numbers.
Sources of information:
Anonamous. 2004. Tamar Valley Weed Strategy- www.weeds.asn.au. http://www.weeds.asn.au/weeds/txts/slen_thstle.html.
Anonomous. 2003. Written findings of the State Noxious Weed Control Board-Class A Weed.
Moore, P.E. and Gerlach, J.D. 2001. Exotic species threat assessment in Ssequoia, Kings Canyon, and Yosemite national parks. Crossing boundaries in park management: proceedings of the 11th conference on research and resource management in parks and on public lands. The George Wright Society.
Cowan, B. 2000. Italian thistles: an ominous threat. California Exotic Pest Plant Council News, 8(1):15.
Massera, J. 2001. More about Italian thistle. California Exotic Pest Plant Council New, spring.
Knapp, J.J. 2004. Catalina Invasive Plant Ranking Plan for the Catalina Island Conservancy. Unpublished.
Elkhorn Slough National Estuarine Research Reserve. 2000. Weed control by species. Elkhorn Slough National Estuarine Research Reserve. Pp. 1-57.
|
Question 2.3 Recent trend in total area infested within state?
Assess the overall trend in the total area infested by this species statewide. Include current management efforts in this assessment and note them.
Select the one letter below that best describes the current trend:
A. Increasing rapidly (doubling in total range statewide in <10 years)
B. Increasing, but less rapidly
C. Stable
D. Declining
U. Unknown
|
B
Other Published Material
|
Describe trend:
San Miguel, Santa Rosa and Catalina islands are invaded, along with the California coast from Mendocino to San Diego counties, lower Sacramento River Valley, Sierra nevada foothills. It is listed as a noxious weed by California State Department of Food and Agriculture. C. pycnocephalus control has occurred at Ring Mountain and Jepson Prairie preserves, Sequoia, Yosomite, Kings Canyon, and Channel Islands National Parks, Inland Empire- California State Parks, Elkhorn Slough National Estuarian Research Reserve, and the Catalina Island Conservancy. Currently 8,324,425 square feet are invaded on Catalina Island.
Sources of information:
Wilken, D. and Hannah, L. 1998. Carduus pycnocephalus. Channel Islands National Park Service Species Literature Review. Unpublished.
Pitcher, D. and Russo, M.J. 1997. The Nature Conservancy Element Stewardship Abstract: Carduus pycnocephalus. California Field Office, San Francisco.
Moore, P.E. and Gerlach, J.D. 2001. Exotic species threat assessment in Ssequoia, Kings Canyon, and Yosemite national parks. Crossing boundaries in park management: proceedings of the 11th conference on research and resource management in parks and on public lands. The George Wright Society.
Knapp, J.J. 2004. Catalina Invasive Plant Ranking Plan for the Catalina Island Conservancy. Unpublished.
California State Parks. 2000. Urban edge effects and their relationship with the natural environment. Pp. 1-30. California State Parks Inland Empire District.
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Question 2.4 Innate reproductive potential?
Assess the innate reproductive potential of this species. Worksheet A is provided for computing the score.
|
B
Other Published Material
|
Describe key reproductive characteristics:
C. pyconocephalus is an annual or biennial that is bisexual and self-compatable. It is pollinated by a diversity of insects. Spreads by seeds only, and is mainly wind dispersed, but seeds become mucilaginous when wetted. Seeds can germinate under water-limiting conditions such as drought. C. pyconocephalus has 83-96% germination rate, with greater germination on clay soils. Seeds remain dormant under shaded conditions, and are thought to remain viable for over 7-10 years in the soil. Individual plants produce hundreds of seeds. Seed can set without vernalisation or stem elongation. Seeds can germinate at lower temperatures (zero to five degrees Celcius) than other thistle species. Presence of musk thistle biocontrol agent (Rhinocyllus conicus) has been reported to reduce seed production by about 50%.
Sources of information:
Wilken, D. and Hannah, L. 1998. Carduus pycnocephalus. Channel Islands National Park Service Species Literature Review. Unpublished.
Anonamous. 2004. Tamar Valley Weed Strategy- www.weeds.asn.au. http://www.weeds.asn.au/weeds/txts/slen_thstle.html.
Pitcher, D. and Russo, M.J. 1997. The Nature Conservancy Element Stewardship Abstract: Carduus pycnocephalus.
Moore, P.E. and Gerlach, J.D. 2001. Exotic species threat assessment in Ssequoia, Kings Canyon, and Yosemite national parks. Crossing boundaries in park management: proceedings of the 11th conference on research and resource management in parks and on public lands. The George Wright Society.
Groves, R.H. and Kaye, P.E. 1989. Germination and phenology of seven introduced thistle species in Southern Australia. Australian Journal of Botany, 37:351-359.
Elkhorn Slough National Estuarine Research Reserve. 2000. Weed control by species. Elkhorn Slough National Estuarine Research Reserve. Pp. 1-57.
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Question 2.5 Potential for human-caused dispersal?
Assess whether this species is currently spread: or has high potential to be spread: by direct or indirect human activity. Such activity may enable the species to overcome natural barriers to dispersal that would not be crossed otherwise, or it may simply increase the natural dispersal of the species. Possible mechanisms for dispersal include:
- commercial sales for use in agriculture, ornamental horticulture, or aquariums;
- use as forage, erosion control, or revegetation;
- presence as a contaminant (seeds or propagules) in bulk seed, hay, feed, soil, packing materials, etc.;
- spread along transportation corridors such as highways, railroads, trails, or canals;
- transport on boats or boat trailers.
Select the one letter below that best describes human-caused dispersal and spread:
A. High: there are numerous opportunities for dispersal to new areas.
B. Moderate: human dispersal occurs, but not at a high level.
C. Low: human dispersal is infrequent or inefficient.
D. Does not occur.
U. Unknown.
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B
Other Published Material
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Identify dispersal mechanisms:
Seeds are dispersed by humans, vehicles, machinery, soil, and hay, but long distance transport is probably uncommon.
Sources of information:
Anonymous. 2003. Written findings of the State Noxious Weed Control Board
Moore, P.E. and Gerlach, J.D. 2001. Exotic species threat assessment in Ssequoia, Kings Canyon, and Yosemite national parks. Crossing boundaries in park management: proceedings of the 11th conference on research and resource management in parks and on public lands. The George Wright Society.
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Question 2.6 Potential for natural long-distance dispersal?
We have chosen 1 km as the threshold of "long-distance." Assess whether this species is frequently spread, or has high potential to be spread, by animals or abiotic mechanisms that can move seed, roots, stems, or other propagules this far. The following are examples of such natural long-distance dispersal mechanisms:
- the species' fruit or seed is commonly consumed by birds or other animals that travel long distances;
- the species' fruits or seeds are sticky or burred and cling to feathers or hair of animals;
- the species has buoyant fruits, seeds, or other propagules that are dispersed by flowing water;
- the species has light propagules that promote long-distance wind dispersal;
- The species, or parts of it, can detach and disperse seeds as they are blown long distances (e.g., tumbleweed).
Select the one letter below that best describes natural long-distance dispersal and spread:
A. Frequent long-distance dispersal by animals or abiotic mechanisms.
B. Occasional long-distance dispersal by animals or abiotic mechanisms.
C. Rare dispersal more than 1 km by animals or abiotic mechanisms.
D. No dispersal of more than 1 km by animals or abiotic mechanisms.
U. Unknown.
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C
Other Published Material
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Identify dispersal mechanisms:
Seed is dispersed mainly by wind; however, mucilagious seeds are dispersed by livestock and short distances by ants. Some movement long distance by animals and by water.
Sources of information:
Anonymous. 2004. Tamar Valley Weed Strategy http://www.weeds.asn.au/weeds/txts/slen_thstle.html.
Moore, P.E. and Gerlach, J.D. 2001. Exotic species threat assessment in Sequoia, Kings Canyon, and Yosemite national parks. Crossing boundaries in park management: proceedings of the 11th conference on research and resource management in parks and on public lands. The George Wright Society.
Brown, K. and Brooks, K. 2002. Bushland Weeds: a practical guide to their management with case studies from the Swan Coastal Plain and beyond. The Environmental Weeds Action Network.
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Question 2.7 Other regions invaded?
Assess whether this species has invaded ecological types in other states or countries outside its native range that are analogous to ecological types not yet invaded in your state (see Worksheets B, C, and D for California, Arizona, and Nevada, respectively, in Part IV for lists of ecological types). This information is useful in predicting the likelihood of further spread within your state.
Select the one letter below that best describes the species' invasiveness in other states or countries, outside its native range.
A. This species has invaded 3 or more ecological types elsewhere that exist in your state and are as yet not invaded by this species (e.g. it has invaded Mediterranean grasslands, savanna, and maquis in southern Europe, which are analogous to California grasslands, savanna, and chaparral, respectively).
B. Invades 1 or 2 ecological types that exist but are not yet invaded in your state.
C. Invades elsewhere but only in ecological types that it has already invaded in the state.
D. Not known as an escape anywhere else.
U. Unknown.
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C
Other Published Material
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Identify other regions:
C. pycnocephalus is invasive in Australia, New Zealand, South Africa, North America, wetern Asia, Iran, and Pakistan. Naturalized in temperate regions around the world.
Sources of information:
Wilken, D. and Hannah, L. 1998. Carduus pycnocephalus. Channel Islands National Park Service Species Literature Review. Unpublished.
Anonomous. 2003. Written findings of the State Noxious Weed Control Board-Class A Weed.
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| Section 3: Distribution |
Question 3.1 Ecological amplitude/Range?
Refer to Worksheet C and select the one letter below that indicates the number of different ecological types that this species invades.
A. Widespread: the species invades at least three major types or at least six minor types.
B. Moderate: the species invades two major types or five minor types.
C. Limited: the species invades only one major type and two to four minor types.
D. Narrow: the species invades only one minor type.
U. Unknown.
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A
Other Published Material
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C. pycnocephalus was introduced to California during the 1930's. It is not listed in either the 1923 or 1967 Santa Catalina Island Floras. In 2003, 200 populations were detected, and the following is the percentage of habitats invaded: bare-<0.00%, beach-<0.00%, coastal bluff scrub-8%, coastal scrub-0.02%, coastal scrub/grassland-0.01%, grassland-1.5%, mixed chaparral-<0.00%, scrub oak chaparral-<0.00%, riparian-0.12%, oak woodland-<0.00%; and the following is the number of populations by non-native communities: 15-roadside, 1-non-native woodland, and 9-non-native herbaceous.
Sources of information:
Anonymous. 2003. Written findings of the State Noxious Weed Control Board-Class A Weed.
Knapp, J.J. 2004. Catalina Invasive Plant Ranking Plan for the Catalina Island Conservancy. Unpublished.
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Question 3.2 Distribution/Peak frequency?
To assess distribution, record the letter that corresponds to the highest percent infested score entered in Worksheet C for any ecological type.
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B
Observational
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Describe distribution:
Very common in Oak woodlands throughout the state.
Sources of information:
Joe DiTomaso, UC Davis, observational
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| Reaches reproductive maturity in 2 years or less |
Yes |
| Dense infestations produce >1,000 viable seed per square meter |
No |
| Populations of this species produce seeds every year. |
Yes |
| Seed production sustained over 3 or more months within a population annually |
No |
| Seeds remain viable in soil for three or more years |
Yes |
| Viable seed produced with both self-pollination and cross-pollination |
Yes |
| Has quickly spreading vegetative structures (rhizomes, roots, etc.) that may root at nodes |
No |
| Fragments easily and fragments can become established elsewhere |
No |
| Resprouts readily when cut, grazed, or burned |
No |
| Total points: |
5
|
| Total unknowns: |
0 |
| Total score: |
B?
Scoring Criteria for Worksheet A
A. High reproductive potential (6 or more points).
B. Moderate reproductive potential (4-5 points).
C. Low reproductive potential (3 points or less and less than 3 Unknowns).
U. Unknown (3 or fewer points and 3 or more Unknowns).
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Related traits:
Worksheet B - Arizona Ecological Types is not included here
(sensu Holland 1986)
| Major Ecological Types |
Minor Ecological Types |
Code?
A means >50% of type occurrences are invaded;
B means 20% to 50%;
C means 5% to 20%;
D means present but <5%;
U means unknown (unable to estimate percentage of occurrences invaded)
|
| Marine Systems | marine systems | |
| Freshwater and Estuarine | lakes, ponds, reservoirs | |
| Aquatic Systems | rivers, streams, canals | |
| estuaries | |
| Dunes | coastal | D, < 5% |
| desert | |
| interior | |
| Scrub and Chaparral | coastal bluff scrub | D, < 5% |
| coastal scrub | C, 5% - 20% |
| Sonoran desert scrub | |
| Mojavean desert scrub (incl. Joshua tree woodland) | |
| Great Basin scrub | |
| chenopod scrub | |
| montane dwarf scrub | |
| Upper Sonoran subshrub scrub | |
| chaparral | D, < 5% |
| Grasslands, Vernal Pools, Meadows, and other Herb Communities | coastal prairie | D, < 5% |
| valley and foothill grassland | D, < 5% |
| Great Basin grassland | |
| vernal pool | |
| meadow and seep | |
| alkali playa | |
| pebble plain | |
| Bog and Marsh | bog and fen | |
| marsh and swamp | |
| Riparian and Bottomland habitat | riparian forest | |
| riparian woodland | D, < 5% |
| riparian scrub (incl.desert washes) | D, < 5% |
| Woodland | cismontane woodland | B, 20% - 50% |
| piñon and juniper woodland | |
| Sonoran thorn woodland | |
| Forest | broadleaved upland forest | D, < 5% |
| North Coast coniferous forest | |
| closed cone coniferous forest | |
| lower montane coniferous forest | |
| upper montane coniferous forest | |
| subalpine coniferous forest | |
| Alpine Habitats | alpine boulder and rock field | |
| alpine dwarf scrub | |
|
Amplitude (breadth): |
A |
|
Distribution (highest score): |
B |
Infested Jepson Regions
Click here for a map of Jepson regions
- Central West
- Great Valley
- Northwest
- Sierra Nevada
- Southwest
- Modoc Plateau
- Desert Province
- Mojave Desert
- Sonoran Desert
