Plant Assessment Form

Centaurea melitensis

Common Names: tocalote; Malta starthistle

Evaluated on: 5/22/03

List committee review date: 06/06/2003

Re-evaluation date:

Evaluator(s)

Joe DiTomaso
UC Davis
Weed Science Program, Robbins Hall, Univ. California, Davis CA 95616
530-754-8715
DiTomaso@vegmail.ucdavis.edu

List commitee members

Joe DiTomaso
Peter Warner
Alison Stanton
Carla Bossard
Cynthia Roye
Jake Sigg
Doug Johnson
Brianna Richardson

General Comments

No general comments for this species

Table 2. Criteria, Section, and Overall Scores

Overall Score? Moderate
Alert Status? No Alert
Documentation? 2.5 out of 5
Score Documentation
1.1 ?Impact on abiotic ecosystem processes B Observational
Impact?
Four-part score BBCD Total Score
B
1.2 ?Impact on plant community B. Moderate Other Published Material
1.3 ?Impact on higher trophic levels C. Minor Other Published Material
1.4 ?Impact on genetic integrity D. None Observational
2.1 ?Role of anthropogenic and natural disturbance in establishment B. Moderate Other Published Material
Invasiveness?
Total Points
11 Total Score B
2.2 ?Local rate of spread with no management C. Stable Observational
2.3 ?Recent trend in total area infested within state C. Stable Observational
2.4 ?Innate reproductive potential
(see Worksheet A)
A. High Other Published Material
2.5 ?Potential for human-caused dispersal B. Moderate Other Published Material
2.6 ? Potential for natural long-distance dispersal C. Rare Other Published Material
2.7 ?Other regions invaded C. Already invaded Other Published Material
3.1 ?Ecological amplitude/Range
(see Worksheet C)
B. Moderate Other Published Material
Distribution?
Total Score B
3.2 ?Distribution/Peak frequency
(see Worksheet C)
C. Low Observational

Table 3. Documentation

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? B Observational
Identify ecosystem processes impacted:

May increase erosion, reduce water percolation. Does not survive as long as yellow starthistle so it is not likely to have same effect on soil moisture depletion.


Sources of information:

DiTomaso-Observational


Question 1.2 Impact on plant community composition,
structure, and interactions?
B Other Published Material
Identify type of impact or alteration:

Dense stands can displace native plants and animals. Significantly reduces seed production of the endangered plant Acanthiminta ilicifolia.


Sources of information:

Question 1.3 Impact on higher trophic levels? C Other Published Material
Identify type of impact or alteration:

Can be poisonous to horses and may cause mechanical damage to wildlife. Probably reduces other better forage species.


Sources of information:

Question 1.4 Impact on genetic integrity? D Observational

None No native Centaurea in California


Sources of information:

DiTomaso-Observational


Section 2: Invasiveness
Question 2.1 Role of anthropogenic and natural disturbance
in establishment?
C Observational
Describe role of disturbance:

Primarily found in disturbed sites, but will move into annual grass dominated grasslands.


Sources of information:

DiTomaso, J.M. and E.A. Healy. 2005. Weeds of California. DANR (pre-print


Question 2.2 Local rate of spread with no management? C Observational
Describe rate of spread:

Seems to be stable in most areas. Has been in California for over 150 years.


Sources of information:

DiTomaso-Observational


Question 2.3 Recent trend in total area infested within state? C Observational
Describe trend:

Stable in northern California. Possibly slightly increasing in southern California. This could be due to confusion in past with yellow starthistle.


Sources of information:

DiTomaso-Observational


Question 2.4 Innate reproductive potential? A Other Published Material
Describe key reproductive characteristics:

Annual with seed production only. Averages 1,500 seeds.plant.


Sources of information:

Question 2.5 Potential for human-caused dispersal? B Other Published Material
Identify dispersal mechanisms:

Probably through human activity including equipment, seed and soil contamination, and vehicles, but because it is not as widespread as yellow starthistle, the rate is not as great.


Sources of information:

Question 2.6 Potential for natural long-distance dispersal? C Other Published Material
Identify dispersal mechanisms:

Short distance wind dispersal. Animals can occasionally move seed longer distances in hair or birds after ingestion. Seeds only blow short distance. Most seed fall to ground just below parent plant.


Sources of information:

Question 2.7 Other regions invaded? C Other Published Material
Identify other regions:

Has invaded other southwestern states to the eastern US, but not reported as a problem in other countries. Similar habitats occupied elsewhere.


Sources of information:

DiTomaso, J.M. and E.A. Healy. 2005. Weeds of California. DANR (pre-print


Section 3: Distribution
Question 3.1 Ecological amplitude/Range? B Other Published Material

Mainly found in grasslands, throughout the state but more commonly in southern California. Introduced as early as 1797.


Sources of information:

DiTomaso, J.M. and E.A. Healy. 2005. Weeds of California. DANR (pre-print


Question 3.2 Distribution/Peak frequency? C Observational
Describe distribution:

Most common in grasslands, probably <20% of the grasslands, however.


Sources of information:

DiTomaso-Observational


Worksheet A - Innate reproductive potential

Reaches reproductive maturity in 2 years or less Yes
Dense infestations produce >1,000 viable seed per square meter Yes
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: 7
Total unknowns: 0
Total score: A?

Related traits:

Worksheet B - Arizona Ecological Types is not included here

Worksheet C - California Ecological Types

(sensu Holland 1986)
Major Ecological Types Minor Ecological Types Code?
Marine Systemsmarine systems
Freshwater and Estuarine lakes, ponds, reservoirs
Aquatic Systemsrivers, streams, canals
estuaries
Dunescoastal
desert
interior
Scrub and Chaparralcoastal bluff scrub
coastal scrub
Sonoran desert scrub
Mojavean desert scrub (incl. Joshua tree woodland)
Great Basin scrub
chenopod scrub
montane dwarf scrub
Upper Sonoran subshrub scrub
chaparralD, < 5%
Grasslands, Vernal Pools, Meadows, and other Herb Communitiescoastal prairieC, 5% - 20%
valley and foothill grasslandD, < 5%
Great Basin grassland
vernal pool
meadow and seep
alkali playa
pebble plain
Bog and Marshbog and fen
marsh and swamp
Riparian and Bottomland habitatriparian forest
riparian woodland
riparian scrub (incl.desert washes)C, 5% - 20%
Woodlandcismontane woodland
piñon and juniper woodland
Sonoran thorn woodland
Forestbroadleaved upland forest
North Coast coniferous forest
closed cone coniferous forest
lower montane coniferous forest
upper montane coniferous forest
subalpine coniferous forest
Alpine Habitatsalpine boulder and rock field
alpine dwarf scrub
Amplitude (breadth): B
Distribution (highest score): C

Infested Jepson Regions

Click here for a map of Jepson regions

  • Cascade Range
  • Central West
  • Desert Province
  • Mojave Desert
  • Sonoran Desert
  • Great Valley
  • Northwest
  • Sierra Nevada
  • Sierra Nevada East
  • Southwest