Plant Assessment Form

Geranium purpureum

Synonyms: Geranium robertianum subsp. purpureum; Pelargonium purpureum

Common Names: little robin

Evaluated on: 27-Dec-16

List committee review date: 25/01/2017

Re-evaluation date:

Evaluator(s)

Mona Robison/Science Program Manager
Cal-IPC
916-802-2004
rrobison@cal-ipc.org

List commitee members

Elizabeth Brusati
Tim Hyland
Eric Wrubel
Irina Irvine
Holly Forbes

General Comments

No general comments for this species

Table 2. Criteria, Section, and Overall Scores

Overall Score? Limited
Alert Status? No Alert
Documentation? 3 out of 5
Score Documentation
1.1 ?Impact on abiotic ecosystem processes U No Information
Impact?
Four-part score UCDC Total Score
C
1.2 ?Impact on plant community C. Minor Observational
1.3 ?Impact on higher trophic levels D. Negligible Reviewed Scientific Publication
1.4 ?Impact on genetic integrity C. Minor/Low Reviewed Scientific Publication
2.1 ?Role of anthropogenic and natural disturbance in establishment B. Moderate Observational
Invasiveness?
Total Points
15 Total Score B
2.2 ?Local rate of spread with no management A. Increases rapidly Observational
2.3 ?Recent trend in total area infested within state A. Increasing rapidly Observational
2.4 ?Innate reproductive potential
(see Worksheet A)
B. Moderate Reviewed Scientific Publication
2.5 ?Potential for human-caused dispersal C. Low Reviewed Scientific Publication
2.6 ? Potential for natural long-distance dispersal C. Rare Reviewed Scientific Publication
2.7 ?Other regions invaded A. Invades 3 or more ecological types Reviewed Scientific Publication
3.1 ?Ecological amplitude/Range
(see Worksheet C)
A. Widespread Other Published Material
Distribution?
Total Score B
3.2 ?Distribution/Peak frequency
(see Worksheet C)
D. Very low Other Published Material

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? U No Information
Identify ecosystem processes impacted:

There is no information available on G. purpureum's impact on abiotic ecosystem processes. This question is scored as Unknown based on lack of reported abiotic effects.


Sources of information:

Question 1.2 Impact on plant community composition,
structure, and interactions?
C Observational
Identify type of impact or alteration:

"Geranium purpureum is a major player that has taken over Sonoma Valley. I have a drainage at the Bouverie Preserve which had a small patch 4 years ago. The following year it had expanded to several acres, and several new occurrences. I find it to be much more invasive than G. robertianum, which has infested all 4 canyons of Bolinas Lagoon Preserve but never forms the thick stands of G. purpureum" (Gluesenkamp pers comm.).
G. purpureum causes minor alteration of plant communities by increasing the density of the herbaceous layer in forests/woodlands in Sonoma and Napa counties. Emails from Warner, Ruygt and Wrubel (2017) indicate that G. purpureum occasionally outcompetes understory spp. In forests and woodlands. It invades a previously unoccupied niche in bare litter/duff of forests with sparse understory. In brighter locations it outcompetes with native herbs such as Trientalis and Nemophila heterophila and may form > 80% of the ground cover (Ruygt, pers. comm.).


Sources of information:

Gluesenkamp, D. Personal communication.
Ruygt, J. Personal communication.
Warner, P. Personal communication.
Wrubel, E. Personal communication.

RECOMMEND SCORE OF C: MINOR ALTERATION OF PLANT COMMUNITY, (OR B: MODERATE) BY INCREASING DENSITY OF HERBACEOUS LAYER IN FORESTS/WOODLANDS IN SONOMA AND NAPA CO. EMAILS FROM WARNER, RUYGT AND WRUBEL INDICATE THAT G. PURPUREUM OCCASIONALLY OUTCOMPETES UNDERSTORY SPP. IN FORESTS AND WOODLANDS. INVADES PREVIOUSLY UNOCCUPIED NICHE IN BARE LITTER/DUFF OF FORESTS WITH SPARSE UNDERSTORY (RUYGT). EW CHANGED TO MINOR BASED ON EXPERT FEEDBACK MR.


Question 1.3 Impact on higher trophic levels? D Reviewed Scientific Publication
Identify type of impact or alteration:

There is no information available on G. purpureum's impact on higher trophic levels. Herrera (1991) found that 90% of experimental G. purpureum transplants exposed to vertebrate herbivores (cattle, red deer Cervus elephas, fallow deer Dama dama and rabbits Oryetolagus cunic ulus) were consumed well before reaching reproductive size whereas 60% of transplants protected from grazing set at least one fruit.


Sources of information:

Herrera 1991
Tofts 2004


Question 1.4 Impact on genetic integrity? C Reviewed Scientific Publication

G. purpurem can self pollinate as well as cross pollinate. There is no documentation of it hybridizing with native Geranium species in California. Only two native California Geranium species -- Geranium bicknellii and Geranium carolinianum -- overlap with the current range of G. purpureum and could potentially hybridize. There are also many more non-native geraniums occurring in these areas (such as G. dissectum) which would be more likely to hybridize with natives and cause population changes.


Sources of information:

Calflora 2016
Tofts 2004


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

Sources of information:

Cal-IPC PAF for G. dissectum, G. molle and G. robertianum.
Ruygt, J. Personal communication.
Warner, P. Personal communication.


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

Local rate of spread of G. purpureum in California without management appears to be high based on the following: Geranium purpureum is a major player that has taken over Sonoma Valley. I have a drainage at the Bouverie Preserve which had a small patch 4 years ago. The following year it had expanded to several acres, and several new occurrences (Gluesenkamp, pers. comm.)
Where I have seen it, I would say Geranium purpureum is doubling in the East Bay hills, and increasing, but less rapidly near the coast in Golden Gate NRA, and Point Reyes NS (Wrubel, pers. comm.). Ruygt reports it as spreading less rapidly in Napa and Warner reports it as doubling in 10 years in Sonoma County, so the highest rate of spread is selected for this question.


Sources of information:

Gluesenkamp, D. Personal communication.
Ruygt, J. Personal communication.
Warner, P. Personal communication.
Wrubel, E. Personal communication.


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

Local rate of spread of G. purpureum in California without management appears to be high based on reports from regional experts. Where I have seen it, I would say Geranium purpureum is doubling in the East Bay hills, and increasing, but less rapidly near the coast in Golden Gate NRA, and Point Reyes NS (Wrubel, pers. comm.). Ruygt reports it as spreading less rapidly in Napa and Warner reports it as doubling in 10 years in Sonoma County (Ruygt and Warner, pers. comms.), so the highest rate of spread is selected for this question.


Sources of information:

Gluesenkamp, D. Personal communication.
Ruygt, J. Personal communication.
Warner, P. Personal communication.
Wrubel, E. Personal communication.


Question 2.4 Innate reproductive potential? B Reviewed Scientific Publication
Describe key reproductive characteristics:

Reproduces by seed and is an annual or biennial so produces seed in one or two years. Flowers in California from March to October (Rugyt pers. comm.). In Spain, peak flowering occurs in March and seed dispersal and senescence in May. Based on studies in Europe, It appears plants flower and set seed rapidly after germination but do not have a long flowering period. Seeds appear to have short dormancy and germinate as soon as winter starts. Seeds sown in the autumn in Britain germinate soon afterwards. No scarification is required. Seed production per flower is low -- one study found that many flowers produced fewer than 5 viable seeds. Geranium can facultatively self-pollinate, which it regularly does. Seeds remain viable for at least 7 years.


Sources of information:

Calflora 2016
DiTomaso and Healy 2007
Herrera 1991
Tofts 2004


Question 2.5 Potential for human-caused dispersal? C Reviewed Scientific Publication
Identify dispersal mechanisms:

Sources of information:

Baltisberger and Waser-Walter 2009
Ruygt, J. Personal communication.
Warner, P. Personal communication.


Question 2.6 Potential for natural long-distance dispersal? C Reviewed Scientific Publication
Identify dispersal mechanisms:

Geranium seeds lack obvious adaptations promoting dispersal through wind or water. Seed collecting by ants has never been observed (Herrera 1991).
Seed dispersal distances are short. Seeds use ballistic dispersal over short distances with 50% of seeds landing within 44cm of the parent plant. Tortoises in Spain ingest and defecate seeds and other animals could do the same. Since the diaspores are sticky, attachment to animals could play a role in dispersal.


Sources of information:

Herrera 1991
Tofts 2004


Question 2.7 Other regions invaded? A Reviewed Scientific Publication
Identify other regions:

Sources of information:

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

G. purpureum was first collected in Napa county in 1976, and was not collected elsewhere in the Bay Area until the 1990s. It was collected in Butte County starting in 2008 and in Santa Cruz County in 2013, indicating its spread outward from Napa and the Bay Area. There is not a lot of information on the types of habitats that G. purpureum occurs in. Descriptions appear to be for oak woodland and grasslands, as well as urban areas and roadsides. Noted as spreading rapidly in riparian and woodland of inner North Coast ranges of California (Gluesenkamp, pers. comm.).

It grows in mixed hardwood conifer forest where previously cover was sparse and primarily duff. It occurs from Carneros Valley area to Calistoga on the west range of Napa Valley, along the Napa River and more locally in the eastern part of the county. I have not seen it on the east side of Lake Berryessa. I have seen it in oak woodlands, riparian woodlands and in ruderal settings (Rugyt pers. comm.).


Sources of information:

CCH 2016
Calflora 2016
Jepson eFlora 2016
Gluesenkamp, D. Personal communication.
Ruygt, J. Personal communication.
Warner, P. Personal communication.


Question 3.2 Distribution/Peak frequency? D Other Published Material
Describe distribution:

G. purpureum occurs in 10 counties in California and is noted to be spreading rapidly in oak woodlands, riparian woodlands and in ruderal settings (Rugyt pers. comm.). However, the proportion of these community types overall throughout California is < 5%.


Sources of information:

CCH 2016
Calflora 2016
Jepson eFlora 2016
Ruygt, J. Personal communication.


Worksheet A - Innate reproductive potential

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?

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
chaparral
Grasslands, Vernal Pools, Meadows, and other Herb Communitiescoastal prairie
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 forestD, < 5%
riparian woodlandD, < 5%
riparian scrub (incl.desert washes)
Woodlandcismontane woodlandD, < 5%
piñon and juniper woodland
Sonoran thorn woodland
Forestbroadleaved upland forest
North Coast coniferous forestD, < 5%
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): D

Infested Jepson Regions

Click here for a map of Jepson regions