San Francisco State University
Department of Geography
Geography 316:  Biogeography

In progress 12/18/2001

The Biogeography of  the San Francisco Wallflower
Erysimum franciscanum G. Rossb.

Debra Dwyer
Geography 316
Fall 2001

 

Taxonomic Classification

Kingdom: Plantae
Subkingdom: Tracheobionta
Superdivision: Spermatophyta
Division: Magnoliophyta
Class: Magnoliopsida
Subclass: Dilleniidae
Order: Capparales (also Brassicales)
Family: Brassicaceae (formerly Cruciferae)
Genus: Erysimum L.
Species: Erysimum franciscanum G. Rossb
 
                                  (USDA Undated) 


Common name:  San Francisco wallflower or Franciscan wallflower
  Figure 1.  Erysimum franciscanum.  Credit:  Presidio Park
  Stewards: National Park Service, California Academy of
  Sciences. 2001.  

In February or March as the cool, rainy winter ends Erysimum fransiscanum, commonly known as the San Francisco wallflower or Franciscan wallflower, decorates coastal scrub, dune and bluff communities in the San Francisco Bay Area.  The common name ‘wallflower’ for Erysimum derives from the common wallflower, Cheiranthus cheiri or Erysimum cheiri, a European wildflower that was often seen growing through the narrow cracks of old stone walls.  Now it is also cultivated as an ornamental species for gardens (Rossbach 1940; Price 1987).  George Rossbach named the San Francisco wallflower, a local native species, in the late 1930s while researching his dissertation on the genus Erysimum at Stanford University and later published his work in Aliso (Rossbach 1940, 1958). 

Topics covered on this page.

I. Natural History
    A. Description
    B. Habitat
    C. Reproduction
II. Distribution
III. Evolution
IV. Interesting information
    A. California Native Plant Society Listing and Endangered Status
    B. Restoration efforts in San Francisco
V. Other Links
VI. References

Natural History

Description

Erysimum franciscanum is an ornamental member of the Mustard Family, scientific name Brassicaceae (formerly recorded as Cruciferae).  It is a biennial or short-lived perennial herb found in coastal areas from Sonoma County to Santa Cruz County in California (See Distribution).  One to several delicate stems extend from 2 inches to 18 inches above a rosette (See Figure 2).  Coastal forms are suffrutescent, meaning that the lower portion of the stem is woody while the upper portion is herbaceous. Its thin basal leaves are between 1 to 6.5 inches long and gradually tapered toward the stalk.  These leaves have wavy “teeth” which point outward (See Figure 3 below).  The stems branch above into one or several racemes.  At the end of each raceme is a spherical cluster of eye-catching, cream-colored flowers.  (Price 1987; Rossbach 1940). 
Figure 2.  Erysimum franciscanum (Wang 2001).
Figure 3.  Erysimum franciscanum leaf (Dwyer 2001).

Flower morphology is one of the defining characteristics of Brassicaceae.  Almost without exception, the flowers of this family consist of four sepals, four petals arranged to form the shape of a cross, and six stamens, four long and two short (Rollins 1993; Legrand 1988).  

Erysimum found in western North America display some of the largest flowers of all the Brassicaceae.  E. franciscanum also exhibits a cruciform flower with petals up to an inch long that narrow to a claw (See Figure 4).  In its northern range, flower petals are typically cream-colored, but in other areas petal color may be pale yellow or occasionally rich yellow as it is in the southern portion of its range (Price 1987; Rossbach 1940; Rollins 1993).  During its first year, growth of a rosette without flowers is usual (Rossbach 1940).  In later years, E. franciscanum blossoms from February to April and occasionally into June (Price 1987; Rossbach 1940).  However, other accounts give its flowering time between March and June (Corelli and Chandik 1995; CNPS 2001). 
Figure 4.  Erysimum franciscanum
 flower (Price 1987).

Figure 5. Silique, the fruit of Brassicaceae.
 (Durrell and Harrington 1957)		 The fruit of the family Brassicaceae are unique and have been named siliques.  They have two-chambers separated by a thin membrane (Rollins 1993).  The frame of the membrane is called the replum.  The siliques of E. franciscanum are long and narrow as in Figure 5.  They are at least three times as long as they are wide.  They are somewhat fleshy, but compress slightly as they ripen.  The seeds are attached to the replum.  When mature, the side valves break away.  The seeds remain hanging from the replum and are then available for dispersal by animal, or more likely by wind.  Coastal forms of E. franciscanum have winged seeds.  This presumably facilitates dispersal by wind (Price 1987). 

The presence of mustard oil glucosides (glucosinolates) is a distinctive feature of the Brassicaceae family.  Aside from mustard oils, another characteristic of the genus Erysimum are cardenolides found in leaves, stem, and seeds.  These compounds make the juice found throughout certain parts of the plant acrid.  The bitter taste may protect its leaves and stem from predation.  Experiments have shown that several insects such as the larva of pierid butterflies and adult flea beetles which feed on other Brassicaceae spurn Erysimum species (Price 1987).

Habitat

Erysimum franciscanum is a delicate-looking wildflower that prefers open spaces found in coastal scrub and on coastal bluffs.  It  thrives with a fair amount of sunlight (Rossbach 1940). Although it is easily cultivated and does well in San Francisco Bay Area gardens (Hunter 2001), in natural environments, it seeks areas with conditions considered more hostile for plants, preferring to adapt itself to such conditions instead of competing with other species in areas with more favorable conditions (Rossbach 1940).  

Erysimum franciscanum is usually found on unconsolidated, gravely soil.  Most often it grows on disintegrating serpentine soils.  However, this is not a requirement as it is also found on granitic outcrops and in sandy soil (Rossbach 1940; Price 1987).  Serpentinite or serpentine is a rock type derived from the earth's mantle.  It forms in subduction zones where an ocean plate collides with a continental plate and is drawn underneath it.  Serpentine is the state rock of California and occurs throughout central and northern California including the Coast Ranges (California 2001).  Soils developed from this rock are low in nutrients such as potassium and calcium but high in potentially toxic magnesium, chromium, and nickel.  Plants able to survive on these soils such as E. franciscanum have adapted to these chemical conditions (US NPS undated).

Reproduction

E. franciscanum reproduces sexually.  Erysimum spp. usually bloom early in the growing and remain in bloom for three months or more.  Several flowers open at once.  Flowers are fragrant and attract a number of different insects.  Nectar is only produced once upon opening of the flower and dries (Price 1987).  E. franciscanum contains two uniform nectaries at the bases of its lateral stamens.  In addition, median nectaries are also present (Rossbach 1940; Price 1987).  As is usual for Brassicaceae, the nectar produced by this species is hexose-dominant.  It consists of sucrose, glucose and fructose with the ratio of sucrose to the glucose and fructose being less than 0.1.  This type of nectar has been shown to attract butterflies and short-tongued bees (Baker and Baker 1983 in Price 1987).

Little is known regarding specific pollinators for this species.   Grant (1950) lists Erysimum as a genus having no special means of ovule protection that is likely pollinated by long-tongued insects such as bees, wasps, long-tongued flies, moths and butterflies.   Proctor, et al. (1996) note that the common wallflower, E. cheiri, is pollinated by long-tongued bees, and also that members of Brassicaceae are pollinated mainly by bees and sometimes by butterflies or moths.

A significant amount of pollen is produced by the four median anthers at the top of the flower.  Additional amounts are produced by the two lateral anthers which open a short time later.  In general, the anthers do not touch the stigma which along with partial self-incompatibility, hinders self-fertilization (Price 1987).  The large number of pollen grains produced per flower is characteristic of species in which cross-fertilization is common.  Brassicaceae exhibit sporophytic self-incompatibility.  That is to say, a plant cannot be fertilized by pollen from itself due to ‘recognition’ of protein on the coat of the pollen by the stigma surface.  This is an efficient and advantageous system which prevents plants from breeding with themselves or possibly their nearest neighbors (Proctor, et al. 1996).

Distribution


The Mustard family, Brassicaceae, to which E. franciscanum belongs, is cosmopolitan with continuous distribution.  Members of this family are found on all continents throughout the world except Antarctica (Rollins 1993).  Species in this large family include ornamental species such as sweet alyssum and honesty; vegetables such as cabbage, broccoli, and kale; and weeds (Rollins 1993; Legrand 1988).  Their populations are concentrated in temperate regions of the northern hemisphere with centers of diversity and endemism located in the Irano-Turanian, the Mediterranean, and the western United States (Hedge 1976; Rollins 1993)(See Figure 6 for Eurasian and north African distribution).  The family’s cosmopolitan status results from representation in many different habitats including difficult and specialized environments such as high elevations and deserts (Hedge 1976).

 

Figure 6. Brassicaceae Distribution Centers: 1 - Irano-Turnaian, 2 - Saharo-Sindian, 3 - Mediterranean  (Hedge 1976).

 

Erysimum is a cosmopolitan genus containing between 180 to 200 species with continuous distribution concentrated in the northern hemisphere (Rollins 1993).  Like its family Brassicaceae, there are concentrations in eastern Europe and southwest Asia as well as North and Central America where it can be found from the Arctic to Costa Rica (Rossbach 1940; Rollins 1993).  Members are found from low elevations to high alpine settings.  There are nineteen species of Erysimum in North America.  Of those, sixteen are indigenous including E. franciscanum (Rollins 1993).

 

E. franciscanum is a relatively rare herb endemic to the San Francisco Bay Area.  It is found in coastal areas from Sonoma to northern Santa Cruz counties (See Figure 7).  Its distribution is discontinuous in that populations are dependant on soil characteristics and neighboring vegetation.  While it is most often found on disintegrating serpentine soils, it is also found on granitic outcrops as well as on sandy soil (Rossbach 1940; price 1987). 

Rossbach (1940) and the Association for Biodiversity (2001) identify a population of E. franciscanum in Oregon.  However, Price (1987) performed extensive qualitative and quantitative analysis and concluded that the Oregon species were in all likelihood actually E. capitatum.  Rollins (1993) also attributes the Oregon populations to other Erysimum species.  
Figure 7. San Francisco Wallflower Distribution.  (Dwyer 2001 after CalFlora Database 2001)

 

Evolution

 

E. franciscanum belongs to the class of plants called angiosperms, the flowering plants.  For these plants, the flower contains the portions of the plant required for reproduction.  Scientists are still unlocking the phylogeny of angiosperms, but the process has been hindered due to an incomplete fossil record.  Prior classifications sought to determine the origin of these plants by grouping them based on structure, and then identifying primitive characteristics to determine a logical progression.  Taxonimists such as Cronquist (1981) and Hutchinson (1973) placed Brassicaceae (Cruciferae) in different orders with different ancestry.

 

Cronquist (1981) placed Brassicaceae in the subclass Dilleniidae which are woody or herbaceous dicots containing repellants such as tannins or mustard oil glucosides.  The majority of species belong to the following five orders: Violales, Capparales, Ericales, Theales and Malves.  Pollen thought to be from Dilleniidae has been dated to the beginning of the Upper Cretaceous suggesting that Dilleniidae diverged from Magnoliidae at about the same time as Hamamelidae and Rosidae (Cronquist 1981).  Cronquist (1981) believed that Theales were the central group in the Dilleniidae from which the order Capparales including E. franciscanum arose. 

 

Hutchinson (1973) places Brassicaceae in the order Brassicales.  He notes this is a climax group in Rhoeadales derived from the Poppy family (Papaveraceae) which is related to Ranunculaceae, one of the primitive orders of the Dicots.   

 

Within the literature regarding the phylogeny of angiosperms, recent methods elucidating genetic traits within the plant families are leading to a shift toward monophyly (the belief that the angiosperms developed from a single ancestor) (Donoghue 1994; APG 1998).  These new theories place higher weight on cladistics rather than the phenetics previously used by taxonimists such as Cronquist (1981).  A recent ordinal classification renames the order Capparales as Brassicales and places it as a eurosid II within the core eudicots (APG 1998) (See Figure 8). 

With respect to Brassicaceae, the above referenced cladogram is based in part on the work of Rodman (1991) who believed it might be possible to discover a tree linking all of the families which exhibit mustard oil glucosides.  These previously had been dispersed among several orders.  His work reinforces the connection between the Caper family and the Mustard family as well as showing a closer relationship between those families and Salvadoraceae, Bataceae, and Koeberliniaceae (Rodman 1991).
Figure 8. An ordinal classification for the families of flowering plants (Angiosperm Phylogeny Group 1998).

 

Taxonomically, the species in Erysimum are difficult to classify because there is great inter-species variability as well as narrow gaps between the morphological characteristics of different species (Price 1987; Rossbach 1940; Rollins 1993).  Initial classifications during the eighteenth and nineteenth centuries placed some species now accepted as Erysimum in Cheiranthus.  Rossbach (1940) clarified some placements in his work on North American Erysimum species.  Price (1987) developed further taxonomic refinement for North American species with his identification and analysis of  the Erysimum capitatum alliance found throughout western North America (See Figure 9).  This alliance includes E. franciscanum.

North America has long been identified as a center of diversity and endemism for the Brassicaceae (Rollins 1993).  With respect to the genus Erysimum, nineteen species occur in North American and of these sixteen are indigenous.  Widespread species Erysimum capitatum, the Douglas wallflower, is found throughout western North America.  Price (1987) identified Erysimum capitatum alliance as a natural group for specific evolutionary studies based on their sharing the unique chromosome number equal to eighteen .  Price (1987) performed crossing studies within this alliance.  For all combinations that he attempted, he recovered some well-formed, viable seeds.  Thus there is high crossability between these species (Price 1987).  New species may have resulted from hybridization at some point in the past.

Even though these species proved highly crossable in a test garden, in natural settings their distributions are allopatric (geographically isolated) so there is little chance for hybridization (Price 1987).  The most widespread species of the alliance is E. capitatum, the Douglas wallflower.  It has the most variation in form and is found in the widest range of habitats.  A number of the other species in the alliance including E. franciscanum are narrow endemics whose distributions are at the periphery of E. capitatum.  These species are commonly associated and may be somewhat restricted to certain substrates.

Conspectus of the Erysimum capitatum alliance

E. occidentale (S. Watson) Robinson
E. teretifolium Eastw.
E. asperum (Nutt.) DC.
E. ghiesbreghtii J.D. Smith
E. capitatum (Douglas ex Hook.) E. Greene
     subsp. capitatum
     subsp. yukonense R. Price
     subsp. bealianum (Jepson) R. Price
     subsp. argillosum (E. Greene) R. Price
     subsp. angustatum (E. Greene) R. Price
     subsp. lompocense (Rossbach) R. Price
     subsp. perenne (S. Watson ex Cov.) R. Price
     subsp. arenicola (S. Watson) R. Price
     subsp. tolucense R. Price
E. concinnum Eastw.
E. menziesii (Hook.) Wettst.
     subsp. menziesii
     subsp. eurekense R. Price
     subsp. yadonii R. Price
E. ammophilum A.A. Heller
E. franciscanum Rossbach
E. moranii Rollins
E. insulare E. Greene
     subsp. insulare
     subsp. suffrutescens (Abrams) R. Price
     subsp. grandifolium (Rossbach) R. Price

Figure 9.  Conspectus of the Erysimum capitatum alliance (Price 1987).
In his quantitative and qualitative study of the E. capitatum alliance, Price (1987) determined primitive and derived states for thirteen morphological characters using comparisons with E. perofskianum, an Asian species similar to E. capitatum in morphology (see Figure 10).  Following his analysis of these characters, Price concluded that the common ancestor for this alliance is similar to E. capitatum itself.  Given the possibility of hybridization, he further concluded that E. franciscanum as well as E. asperum, E. ghiesbreghtii and E. teretifolium might be a direct descendants of various species of E. capitatum.  However, further research including increased number of morphological characters is needed to fully resolve the phylogeny of this alliance (Price 1987).
Figure 10.  Probable character polarities in the Erysimum capitatum alliance
 (Price 1987).

 

Interesting information

 

California Native Plant Society Listing and Endangered Status

E. franciscanum is not listed as endangered at either the state or federal level (DFG 2001).  However, the California Native Plant Society (CNPS) (2001) has identified E. franciscanum as List 4, Plants of Limited Distribution.  CNPS recommends plants on this list be watched since their distribution is uncommon throughout California.  Vulnerability to threat is low at this time, but the plant's limited distribution is cause for concern.

Although not given on the current CNPS web page, past publications including the California Department of Fish and Game's "Special Vascular Plants, Bryophytes, and Lichens List" show R-E-D CODE for E. franciscanum as 1-2-3 meaning the following:

Rarity (1):   Rare, but the potential for extinction is low.  This species is uncommon enough that its status should be monitored. 

Endangerment (2):  Endangered in a portion of its range.  E. franciscanum is considered to be threatened in northern Santa Cruz county.

Distribution (3):  Endemic to California.

                        ( DFG 2001; Corelli and Chandik 1995)

 Restoration efforts in San Francisco

In San Francisco two organizations are working to preserve, protect, and restore populations of E. franciscanum.  These are the Native Plant Nursery at the Presidio and the Significant Natural Resource Areas Program of San Francisco Recreation and Park Department.

The Native Plant Nursery is located in the Presidio, part of Golden Gate National Recreation Area.  The objective at the nursery is to propagate native plants for return to the watershed where their vegetation restoration project is occurring.  E. franciscanum is one of the native plants in their program.  In general, the nursery staff collects seeds, propagates the plants, and transfers the new plants back to where the seeds were originally collected (Hunter 2001).  They collect the seeds throughout the plants' ripening period in order to preserve genetic variability between plants which produce seeds early and those which produce them later (Chasse 2001).

 
Figure 10.  Flat of E. franciscanum (San Francisco Wallflower) at the Native Plant Nursery at the Presidio, GGNRA, San Francisco.  (Dwyer 2001)

Since E. franciscanum grows on serpentine soils as well as on dune sands in the restoration area, the nursery staff collects seeds from both substrates.  They return new plants to the appropriate area based on where the seeds were originally collected (Chasse 2001).  Although it is easily propagated, the mortality rate for E. franciscanum outplanted to the dune restoration project has been high.  The cause is unknown at this time (Chasse 2001). 

In addition, the San Francisco Recreation and Park Department’s Significant Natural Resource Areas Program (SFNAP) has designated E. franciscanum as a sensitive species and given priority to protecting existing populations as well as restoring this plant within designated natural areas in San Francisco (EIP 2001).

Other Links

 

The CalFlora Database. 2001.  Taxon report for Erysimum franciscanum.
http://www.calflora.org/cgi/calflora_query?where-taxon=Erysimum+franciscanum
         

California. Department of Fish and Game. July 2001. [Online]. "Special Vascular Plants, Bryophytes, and Lichens List."  Available at http://www.dfg.ca.gov/whdab/spplant.pdf. 

 

California Native Plant Society, Yerba Buena Chapter. "Focus on Rarities: San Francisco Wallflower."
http://www.cnps-yerbabuena.org/rare_erysimum_fr.html

 

U. S. National Park Service. “Presidio of San Francisco, Golden Gate National Recreation Area, Rare and Endangered Plants, San Francisco wallflower." http://www.nps.gov/prsf/nathist1/nathist/wallflwr.htm

 

References 

Angiosperm Phylogeny Group (APG). 1998. “An Ordinal Classification for the Families of Flowering Plants.” Annals of the Missouri Botanical Garden. 85(4): 531 – 553. 

Association for Biodiversity. 2001. NatureServe: An online encyclopedia of life [web application]. Version 1.5. Arlington, Virginia, USA. Available: http://www.natureserve.org/servlet/NatureServe?sourceTemplate=species_RptDistribution.wm.  [27 September 2001]. 

Baker H.G., and I. Baker. 1983. Floral nectar sugar constituents in relation to pollinator type. In Handbook of experimental pollination ecology.  C.E. Jones and R. Little. Eds. Pp 117-141. New York: Scientific and Academic Editions. As cited in Price, R.A. 1987. “Systematics of the Erysimum Capitatum Alliance (Brassicaceae) in North America.” Ph.D. dissertation. University of California, Berkeley, California.

 The CalFlora Database. [web application]. 2001.  Taxon report for Erysimum franciscanum.  Distribution data from
            Dean W. Taylor Herbarium Specimens. http://www.calflora.org/cgi/calflora_query?where-taxon=Erysimum+franciscanum
            [Accessed 20 October 2001]. 

California Native Plant Society. 11 November 2001.[Online].  "6th Inventory of Rare Plants - online edition, Status: record erysimum_franciscanum "  Available at http://northcoast.com/~cnps/cgi-bin/cnps/sensinv.cgi/Show?_id=erysimum_franciscanum&sort=&search=. Accessed 20 November 2001.

California. Department of Conservation. Division of Mines and Geology (DMG). 7 November 2001. [Online] "DMG Note 14... Serpentine: California State Rock." . Avaliable: http://www.consrv.ca.gov/dmg/pubs/notes/14/index.htm. [Accessed 19 November 2001].

California. Department of Fish and Game (DFG). July 2001. [Online]. "Special Vascular Plants, Bryophytes, and Lichens List."  Available at http://www.dfg.ca.gov/whdab/spplant.pdf. [Accessed 20 November 2001].

Chasse, M. 2001.  Nursery Manager, Native Plant Nursery, The Presidio, Golden Gate National Parks Association. Personal communication with author November 15, 2001.

Corelli, T. and Z. Chandik. 1995. The Rare and Endangered Plants of San Mateo and Santa Clara County. Half Moon Bay, California: Monocot Press. 

Cronquist, A. 1981. An Integrated System of Classification of Flowering Plants. New York: Columbia University Press. 

Donoghue, M. 1994. ‘Progress and Prospects in Reconstructing Plant Phylogeny.” Annals of the Missouri Botanical Garde.  81(3): 405 – 418. 

EIP Associates. 2001. Unpublished Draft Environmental Management Plan for San Francisco Significant Natural Resource Areas.  San Francisco: EIP Associates.

Grant, V. 1950 “Protection of Ovules in Flowering Plants.” Evolution. 4(3): 179 – 201. 

Harrington, H.D., and L.W. Durrell. 1957. How to Identify Plants. Athens, Ohio: Swallow Press. 

Hedge, I.C. 1976. “A Systematic and Geographical Survey of the Old World Cruciferae.”  In The Biology and Chemistry of the Cruciferae. ed. J.G.Vaughn, A.J.Macleod, and B.M.G.Jones. 1976. London: Academic Press, Inc. 

Hunter, C. 2001.  Nursery Manager, Native Plant Nursery, The Presidio, Golden Gate National Parks Association. Personal communication with author November 3, 2001.

Hutchinson. J. 1973. The Families of Flowering Plants. 3rd ed. Oxford: The Clarendon Press. 

Legrand, B.1988. “Docent Training, Strybing Arboretum Society, Final Project: Plant Families (Cruciferae). ” Unpublished. Strybing Arboretum Library. San Francisco, California. 

Price, R.A. 1987. “Systematics of the Erysimum Capitatum Alliance (Brassicaceae) in North America.” Ph.D. dissertation. University of California, Berkeley, California. 

Proctor, M., P.Yeo, and A. Lack. 1996. The Natural History of Pollination. Portland, Oregon: Timber Press. 

Rodman. J.E. 1991. “A Taxonomic Analysis of Glucosinolate-producing Plants, Part 2: Cladistics.” Systematic Botany. 16(4): 619-629. 

Rollins, R.C. 1993. The Cruciferae of Continental North America: Systematics of the Mustard Family from the Arctic to Panama. Stanford, California: Stanford University Press. 

Rossbach. G.B. 1940. “Erysimum in North America.” Ph.D. dissertation. Stanford University.  Stanford, California. 

____________.1958.  “New taxa and new combinations in the genus Erysimum in North America.” Aliso. 4(1): 115-124. 

United States. Department of Agriculture (USDA). undated. PLANTS classification. [Online]. Available: http://plants.usda.gov/plants/cgi_bin/output_report.cgi?ERFR3. [9 Ocotber 2001]. 

United States. National Park Service. Undated. “Presidio of San Francisco, Golden Gate National Recreation Area, Rare and Endangered Plants.” [Online]. Available: http://www.nps.gov/prsf/nathist1/nathist/rare.htm. [October 31, 2001].

______.  National Park Service. Undated. “Presidio of San Francisco, Golden Gate National Recreation Area,  Serpentinite.” [Online]. Available: http://www.nps.gov/prsf/geology/serpent.htm [19 November 2001].

Wang. T. 2001. Unpublished drawing for the San Francisco Department of Recreation and Parks Significant Natural Areas Program.

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