by Sayaka Eda, student in Geography 316, Fall 1999
San Francisco State University
Geography 316: Biogeography
The Biogeography of Cape Ivy (Delairea
odorata)
by Sayaka Eda, student in Geography 316, Fall 1999
Kingdom: Plantae
Division: Magnoliophyta
Class: Magnoliopsida
Order: Asterales
Family: Asteraceae
Genus: Delairea (Senecio)
Species: D. odorata (S. mikanioides)
Description:
Delairea odorata (previously known as Senecio
mikanioides) is known as Cape Ivy or German Ivy which is native to South Africa
(Hickman 1993). It is a perennial liana with fleshy bright waxy green colored
leaves (San Francisco Recreation and Park Department 1999). Usually, its leaf has
six pointed sharply palmate lobes (Fagg 1989). Its clustered yellow flowers bloom in May
in the Cape region of South Africa (Eloff 1984), but in California, the blooming season is
from December to March (Munz 1959). The blooming season is different because
California and the Cape region are in the different hemisphere. This plant favors
moist, semi-shaded area such as forest margin and wet gullies (Fagg 1989). It
reproduces by root from every leaf node and also seed (SFRPD 1999).
Natural History:
Since South Africa was on the immigration route during
the European Colonization, many plants were accidentally carried along and settled where
the climate was favorable to those plants (Scott, 1992). Along with those plants, D.
odorata have been introduced and used for landscaping around buildings because of its
apparent attractiveness and its rapid growth (SFRPD 1999). Now it has been naturalized
throughout California coastal riparian regions, and recently reported that it is even
increasingly spreading into inland and drier regions (Sigg 1999). D. odorata
rapidly grows and covers the original vegetation beneath, and keeps it from sunshine. It
does not only invade habitat for the native plant species, but also affects aquatic life
that inhibits riparian areas. As many Senecio species contain alkaloids, which is
very toxic to other living organisms (Heywood 1977), D. odorata also seems to have
possibility of poisoning of aquatic environment. There is evidence that shows
toxicity to aquatic organisms such as freshwater shrimp, and habitat of Coho salmon (Sigg
1999). D. odorata is now listed as “most invasive and damaging wild land
pest plants by California Exotic Pest Plant Council (1999). Also in Australia, it is
considered as “Victoria’s more serious environmental weeds” (Fagg, 1989).
Evolution:
The family of D. odorata, Asteraceae
(also called Compositae) is the largest and most abundant family among plant
families. Asteraceae is now found on every continent except Antarctica
(Heywood 1977). It is the latest born family among angiosperm and has existed since
Cretaceous period. Its distribution is considered to be conducted by Continental Drift and
became abundant since Miocene epoch which is in late Tertiary period (Heywood 1977).
The largest tribe within the family, Senecioneae, contains approximately 120 genera
and more than 6,000 species (Bremer 1994). This particular plant used to be
categorized as genus Senecio; however, later on, it was separated from Senecio
and given independent genus Delairea (Barkely comm. per. 1999). Delairea
has only one species, D. odorata (Bremer 1994). Its closest relative is Senecio
mandraliscae (Blue Ice Plant). The evolutionary information on this specific
species was not
available.
Distribution:
The distribution of D. odorata within South
Africa is limited from east Cape to Port Elizabeth (Eloff, 1984) where its climate is
shown as Mediterranean (Cs) and Marine West Coast Forest (Cf, Cs) by Koeppen-Geiger
climate classification. The distribution on North America continent is also limited to Cf
and Cs climate, which is coastal California and Oregon (Sigg 1999). The
California Exotic Pest Plant Council (CalEPPC) specifically states that D. odorata
infests from San Diego to southern coastal Oregon (Sigg 1999). The areas where
it is found within Australia are the regions of South Australia, Victoria, New South
Wales, and Tasmania (Willis, 1972), which are also Cf and Cs climates. The elevation range
is recorded 0 to 656 feet in California (Hickman, 1993). This plant favors moist,
semi-shaded area such as forest margin, wet gullies and canyon along coast(Fagg, 1989);
however, it has been recently invading out of coastal riparian and moving into uplands of
coastal shrubs (Elliot 1994). It is also found in Hawaii where its climate is
different from the origin. In Hawaii, the elevation range becomes higher, which is
between 800-2,000m, because the temperature is too high for D. odorata at lower
elevation (Smith, 1999). The information on its world-wide distribution was not
available; therefore, it is very possible that D. odorata might be found in other
places other than those regions mentioned above.
Map of Distribution:
Other interesting issues:
D. odorata invading forest margin in Pacifica, covering the natural vegetation
beneath.
There are several methods for removal of this plant. Mechanical
removal by hands is effective for small plots; however, the total removal is very
difficult because its root tends to break easily as it is pulled off (Elliot 1994).
Another method is using herbicide, but it only kills exposed leaves (Elliot 1994).
Since its reproduction is by root, complete removal of its root system is necessary.
According to Woody Elliot, an associate resource ecologist at California Department of
Parks and Recreation San Simeon District, the practical solution of controlling D. odorata
is the introduction of organisms which feed on the plant (1994). This type of
removal method is called biocontrol and the biocontrol of D. odorata is now proposed by
California Native Plant Society (Sigg 1999). The similar case of biocontrol of
invasive species is of Senecio jacobaea (commonly known as Tansy ragwort), which is
indigenous to Eurasia and has been invading north coast of California (Elliot 1994).
S. jacobaea has been controlled by introduced insects. Elliot states that if
introducing these kinds of insects that are used for S. jacobaea is not successful,
the importation of insects from its native region which is South Africa for D. odorata,
might be inevitable (1994). Nevertheless, the controversy of how the introducing exotic
species affects the ecosystem remains.
The Year Three Proposal for Biocontrol of Cape ivy by
California Plant Society proposes several processes to control this plant. In April
1999, nationwide surveys and collection of the plant were conducted by scientists of the
Plant Protection Research Institute in South Africa (Sigg 1999). The purpose of the
surveys included identification of insects and other organisms that seem to have impact on
D. odorata. The following research and experiments are designed to determine whether
those insects are specialized and specific enough to this plant without damaging other
organisms and its ecosystem. Those experiments are to be done both in laboratory and
field. It is estimated another three yeas and a total of $63,000 are required to
accomplish the rest of the research (Sigg 1999).
Bibliography
Barkely, T. M. 1999. Personal communication. Botanical Research Institute of
Texas. Tel. (817) 332-4441 ext.30
Bremer, K. 1994. Asteraceae: Cladistics and Classification. Timber Press, Inc. Portland, Oregon.
CalFlora Database. 1999. Senecio mikanioides.
Available:
http://galaxy.cs.berkeley.edu/cgi/calflora_query?where-calrecnum=7512&one=T
[22 Oct 1999]
California Exotic Pest Plant Council. 1999. 1996 Exotic Pest Plant List: List A-1 Most Invasive Wildland Pest Plants. Available: http://www.caleppc.org/ [22 October 1999].
Eloff, J.N., editor. 1984. Plants of the Cape Flora: a descriptive catalogue. Trustees of the National Botanic Gardens of South Africa, Kirstenbosch.
Eric, B.K., D. P. Jeffery. 1995. “The Origin of Dendrosenecio within the Senecioneae (Asteraceae) Based on Chloroplast DNA Evidence.” American Journal of Botany. v.82, p1567-1573.
Fagg, P.C. 1989. “Control of Delairea odorata (Cape Ivy) in Native Forest with the Herbicide Clopyralid.” Plant Protection Quarterly. v.4, n.3, p107-110.
Heywood, V.H., J.B. Harborne, B.L. Turner. 1977. The Biology and Chemistry of the
Compositae. Academic Press, Inc.
New York.
Hickman, J.C. 1993. The Jepson Manual. University of California Press, Berkeley.
Munz, P., D.D. Keck. 1959. A California Flora. University of California Press, Berkelely and Los Angels.
Sigg, J. 1999. “Year Three Proposal for Biocontrol of Cape Ivy.” California Native Plant Society.
Scott, J.K. 1992. “Southern African Plants Naturalized in Australia: A Review of Weed Status and Biological Control Potential.” Plant Protection Quarterly. v.7, n.2, p70-80.
San Francisco Recreation and Park Department. 1999. Habitat Restoration Handbook.
City and County of San Francisco Recreation and Park Department.
USDA, NRCS. 1999. The PLANT Database. Available: http://plants.usda.gov/plants [22 Oct. 1999].
Wills, J.H. 1972. A Handbook to Plants in Victoria, Vol. 2. Melbourne University
Press, Melbourne.
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