Plant Assessment Form

Spartina alterniflora x S. foliosa

Common Names: smooth hybrid cordgrass

Evaluated on: 4-Mar-04

List committee review date: 19/03/2004

Re-evaluation date:

Evaluator(s)

Dr. Debra Ayres
UC Davis
Evolution and Ecology, 1 Shields Ave., Davis, 95616
530 752 6582
drayres@ucdavis.edu
Cynthia L. Roye/ Associate State Park Resource Ecologist
California State Parks, Natural Resources Division
P.O. Box 942896, Sacramento, CA 94296-0001
(916) 653-9083
croye@parks.ca.gov

List commitee members

Carla Bossard
Joe DiTomaso
John Randall
Cynthia Roye
Jake Sigg
Alison Stanton
Peter Warner

General Comments

5/26/17 Note by Ramona Robison
This PAF was originally prepared for Spartina alterniflora x foliosa and S. alterniflora. It has now been revised to include the hybrids, although it is possible that some pure S. alterniflora may still exist in California. Based on conversations with Drew Kerr (Invasive Spartina Project) and Dean Kelch (CDFA). This PAF should be updated to include current references and distribution information.

Table 2. Criteria, Section, and Overall Scores

Overall Score? High
Alert Status? No Alert
Documentation? 3.5 out of 5
Score Documentation
1.1 ?Impact on abiotic ecosystem processes A Other Published Material
Impact?
Four-part score ABAA Total Score
A
1.2 ?Impact on plant community B. Moderate Reviewed Scientific Publication
1.3 ?Impact on higher trophic levels A. Severe Other Published Material
1.4 ?Impact on genetic integrity A. Severe/High Reviewed Scientific Publication
2.1 ?Role of anthropogenic and natural disturbance in establishment A. Severe Reviewed Scientific Publication
Invasiveness?
Total Points
17 Total Score A
2.2 ?Local rate of spread with no management A. Increases rapidly Reviewed Scientific Publication
2.3 ?Recent trend in total area infested within state A. Increasing rapidly Reviewed Scientific Publication
2.4 ?Innate reproductive potential
(see Worksheet A)
A. High Reviewed Scientific Publication
2.5 ?Potential for human-caused dispersal C. Low Anecdotal
2.6 ? Potential for natural long-distance dispersal A. Frequent Observational
2.7 ?Other regions invaded C. Already invaded Reviewed Scientific Publication
3.1 ?Ecological amplitude/Range
(see Worksheet C)
B. Moderate Reviewed Scientific Publication
Distribution?
Total Score C
3.2 ?Distribution/Peak frequency
(see Worksheet C)
D. Very low Reviewed Scientific Publication

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? A Other Published Material
Identify ecosystem processes impacted:

Sediment accretion S. alterniflora (and S. anglica) accrete sediments and elevate marsh surfaces transforming naturally open tidal mudflats into meadows


Sources of information:

Observational information for San Francisco Bay; sediment accretion has been observed in other estuaries (including within native East Coast range); sediment accretion has been documented for S. anglica another maritime cordgrass:
Pringle , A. W. 1993. Spartina anglica colonisation and physical effects in the Tamar Estuary, Tasmania 1971-91. Papers and Proceedings of the Royal Society of Tasmania 127: 1-10


Question 1.2 Impact on plant community composition,
structure, and interactions?
B Reviewed Scientific Publication
Identify type of impact or alteration:

Hybrid cordgrass is invading marshes dominated by native cordgrass. Hybrid cordgrass has shown increased tolerance to salinity and co-occurs with Salicornia virginica in the higher marsh of restoration sites. The main impacts of hybrid cordgrass are the replacement of native cordgrass in existing marshes, the potential replacement of Salicornia virginica dominated marshes, and the invasion and dominance of restored marshes


Sources of information:

Ayres DR, Smith DL, Zaremba K, Klohr S, Strong DR. 2004. Spread of exotic cordgrasses and hybrids (Spartina sp.) in the tidal marshes of San Francisco Bay. Biological Invasions. 6: 221-231
Pakenham, M. R. 2003. Variation in salinity tolerance and competitive ability of invasive Spartina hybrids in San Francisco Bay. Master of Science thesis. University of California Davis.


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

Removal of bird foraging habitat though cordgrass overgrowth of open mud flat habitat Open mudflat is valuable forage ground for migratory and residential shorebirds


Sources of information:

The Pt. Reyes Bird Observatory has assembled a bibliography on maritime cordgrass impacts to shorebirds. An example (for S. anglica):Goss-Custard, J. D., Clarke, R. T., Dit Durell, S. V., Caldow, R. W., and B. J. Ens. 1995. Population consequences of winter habitat loss in a migratory shorebird. II. Model predictions. Journal of Applied Ecology 32: 337-351.


Question 1.4 Impact on genetic integrity? A Reviewed Scientific Publication

Hybrid cordgrass freely interbreeds with native S. foliosa. This is predicted to result in the extirpation of the native species. Hybrid cordgrass is a superior sire on the native and out competes it


Sources of information:

Ayres, D. R., D. R. Strong, and P. Baye. 2003. Spartina foliosa - a common species on the road to rarity? Madrono 50: 209-213.


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

Hybrid colonize the open mud of restoration sites, intertidal foreshores, and naturally caused bare patches in established marshes. The latter 2 occur naturally. Continuing restoration of salt ponds into tidal marsh create ideal recruitment sites for cordgrass seed. Some highly fit hybrids are able to establish in intertidal foreshores and within existing native marshes.


Sources of information:

Ayres DR, Smith DL, Zaremba K, Klohr S, Strong DR. 2004. Spread of exotic cordgrasses and hybrids (Spartina sp.) in the tidal marshes of San Francisco Bay. Biological Invasions. 6: 221-231.
Ayres and Strong, unpublished data.


Question 2.2 Local rate of spread with no management? A Reviewed Scientific Publication
Describe rate of spread:

Exponential to super-exponential Selection on invasive genotypes is leading to the evolution of more invasive genotypes, we hypothesize. This increases the rate of spread to greater-than-exponential.


Sources of information:

Ayres DR, Smith DL, Zaremba K, Klohr S, Strong DR. 2004. Spread of exotic cordgrasses and hybrids (Spartina sp.) in the tidal marshes of San Francisco Bay. Biological Invasions. 6: 221-231.


Question 2.3 Recent trend in total area infested within state? A Reviewed Scientific Publication
Describe trend:

see above


Sources of information:

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

Some hybrids produce inflorescence with 4-fold the number of florets as the native. Some of these are highly fertile and some are highly self-fertile. Some hybrids have high rates of lateral expansion through clonal growth. Some hybrids can sire abundant seed on surrounding S. foliosa plants Long-lived clones, plus high seed set and siring abilities confer high persistance and high reproductive potential on cordgrass hybrids.


Sources of information:

Ayres DR, Smith DL, Zaremba K, Klohr S, Strong DR. 2004. Spread of exotic cordgrasses and hybrids (Spartina sp.) in the tidal marshes of San Francisco Bay. Biological Invasions. 6: 221-231.
Ayres, D. R., D. R. Strong, and P. Baye. 2003. Spartina foliosa - a common species on the road to rarity? Madro o 50: 209-213.
Zaremba K (2001) Hybridization and Control of a Native-Non Native Spartina Complex in San Francisco Bay. Master of Arts thesis, San Francisco State University, San Francisco, California


Question 2.5 Potential for human-caused dispersal? C Anecdotal
Identify dispersal mechanisms:

limited - restricted to restoration that plants S. alternifllora and hybrid plants early in the invasion the above contributed to long distance dispersal and establishment of hybrids. Widespread attention has curtailed this introduction route.


Sources of information:

U. S. Army Corps of Engineers (USACE) (1978) Shoreline erosion control demonstration program. Alameda, California: Preconstruction Report. U. S. Army Engineer District, San Francisco Corps of Engineers, San Francisco, CA
Faber, P. 2000. Good intentions gone awry. Why would anyone bring and alien cordgrass to San Francisco Bay? Coast and Ocean 16 (2).


Question 2.6 Potential for natural long-distance dispersal? A Observational
Identify dispersal mechanisms:

seed floating on the tides; seed contained in rafts of cordgrass wrack Cordgrass seed is able to float for long periods; seed-containing wrack is able to move long distances. Long distance dispersal on tidal currents is feasible.


Sources of information:

Huiskes AHL, Koutstaal BP, Herman PMJ, Beeftink WG, Markusse MM and De Munck W (1995) Seed dispersal of halophytes in tidal salt marshes. Journal of Ecology 83: 559-567;
Kathleen Sayce, personal communication on dispersal of S. alterniflora from Willapa Bay to Greys Harbour, WA


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

S. alterniflora has invaded many estuaries worldwide, most notably, estuaries in Washington State. Open mud flat habitat is natural to the Pacific coast of north America and vulnerable to S. alterniflora invasion


Sources of information:

Janie Civille, PhD research


Section 3: Distribution
Question 3.1 Ecological amplitude/Range? B Reviewed Scientific Publication

S. alterniflora and hybrids grow lower and higher in the marsh than native vegetation. Some hybrids have higher salinity tolerance than native. S. alterniflora was introduced into San Francisco Bay in the mid-1970s - hybrids arisen since this time. Native habitat will be altered due to the wider ecological amplitude of the invader.


Sources of information:

Pakenham, M. R. 2003. Variation in salinity tolerance and competitive ability of invasive Spartina hybrids in San Francisco Bay. Master of Science thesis. University of California Davis.
Callaway, J. C. and M. N. Josselyn. 1992. The introduction and spread of smooth cordgrass (Spartina alterniflora) in South San Francisco Bay. Estuaries 15:218-226.
Zaremba K (2001) Hybridization and Control of a Native-Non Native Spartina Complex in San Francisco Bay. Master of Arts thesis, San Francisco State University, San Francisco, California
Faber, P. 2000. Good intentions gone awry. Why would anyone bring and alien cordgrass to San Francisco Bay? Coast and Ocean 16 (2).
Ayres and Strong, unpublished data.


Question 3.2 Distribution/Peak frequency? D Reviewed Scientific Publication
Describe distribution:

Hybrids have radiated from points of deliberate introduction. Marshes neighboring invaded marshes are especially vulnerable to invasion; restoration sites near invaded marshes have been heavily colonized by hybrids.


Sources of information:

Ayres DR, Smith DL, Zaremba K, Klohr S, Strong DR. 2004. Spread of exotic cordgrasses and hybrids (Spartina sp.) in the tidal marshes of San Francisco Bay. Biological Invasions. 6: 221-231.


Worksheet A - Innate reproductive potential

Reaches reproductive maturity in 2 years or less No
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 Unknown
Seeds remain viable in soil for three or more years No
Viable seed produced with both self-pollination and cross-pollination Yes
Has quickly spreading vegetative structures (rhizomes, roots, etc.) that may root at nodes Yes
Fragments easily and fragments can become established elsewhere No
Resprouts readily when cut, grazed, or burned Yes
Total points: 6
Total unknowns: 1
Total score: A?

Related traits:

Seed production almost doubles in an El Nino year.

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
estuariesD, < 5%
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 grassland
Great Basin grassland
vernal pool
meadow and seep
alkali playa
pebble plain
Bog and Marshbog and fenD, < 5%
marsh and swamp
Riparian and Bottomland habitatriparian forest
riparian woodland
riparian scrub (incl.desert washes)
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): D

Infested Jepson Regions

Click here for a map of Jepson regions