Catalina mahogany (Cercocarpus traskiae)

KingdomPlantae
PhylumTracheophyta
ClassMagnoliopsida
OrderRosales
FamilyRosaceae
GenusCercocarpus (1)
SizeHeight: 3 - 7 m (2)
Trunk diameter: c. 20 cm (2)

The Catalina mahogany is classified as Critically Endangered (CR) on the IUCN Red List (1).

With only seven adult plants remaining in 2002, the Catalina mahogany (Cercocarpus traskiae) is one of the rarest plants in the world (3) (4).

The Catalina mahogany is a small (5), long-lived evergreen tree or shrub with thick, stiff, leathery leaves. The oval leaves are densely covered with hairs on the lower surface (6), and are between 2.5 and 6 centimetres long (2).

The flowers of the Catalina mahogany are produced in clusters of four to ten (6), and do not have petals (7). Each flower produces a dry (6), cylindrical fruit (7) containing a single (6), feathery seed (7).  

The Catalina mahogany is only found on Santa Catalina Island, California (3). Shockingly, only seven pure, mature Catalina mahogany individuals remain, with a further five hybrid plants in existence (4). The mature individuals of this species occur alongside around 100 seedlings and saplings (6) in Wild Boar Gully (4).

The Catalina mahogany is found on just one steep slope on Santa Catalina Island. The coastal slope consists of sage scrub on reddish gabbro soils, which are formed from the breakdown of a type of dark, igneous rock (3).

Due to the Catalina mahogany’s extreme rarity, much is still unknown about this species’ biology.

Like other Cercocarpus species, it is likely that the Catalina mahogany is wind-pollinated. Once fertilisation has taken place, the long, cylindrical fruit develops, which has a long ‘tail’ of white hairs that enables the seeds to be carried by the wind. Ripened fruits of Cercocarpus trees typically disperse from July to October (7).

As a long-lived tree, the Catalina mahogany may take many years to reach maturity (6).

Historically, a major threat to the Catalina mahogany was the introduction of herbivores, such as goats, deer and pigs, to Santa Catalina Island. Goats and deer ate the seedling shoots and the leaves of the tree, while pigs rooting through the ground destroyed seedlings and the roots (6).

Hybridisation with the closely related California mountain mahogany (Cercocarpus betuloides) is currently a significant threat to the Catalina mahogany (6). Already, there are five hybrid plants alongside the seven pure individuals in Wild Boar Gully (4). Hybridisation between different species will result in a loss of genetic diversity which could impact upon the future survival of the Catalina mahogany (6).

Another possible threat comes from non-native invasive plant species. Unfortunately, erecting fences around the remaining Catalina mahogany individuals to exclude herbivores has resulted in a build-up of both native and non-native plant species within the enclosure (6).

The increase in vegetation in the fenced area has also resulted in a potential increase in the risk of fires. Fires on Santa Catalina Island are fairly infrequent, although fires from lightning strikes have occurred, and such events are known to be a threat to seedlings and saplings (6).

Conservation efforts began in the 1970s with a detailed inventory of the remaining Catalina mahogany plants (8). In 1999, the entire Wild Boar Gully area was fenced off, enclosing 45 hectares (4). This action was successful and resulted in the numbers of seedlings and saplings increasing year after year, reaching a peak of 113 individuals in 2002. However, it is not known what portion of these seedlings and saplings are the Catalina mahogany and which are hybrids (6).

An effort has also been made to remove invasive herbivores from Santa Catalina Island. All goats have been removed from the island, and just a small number of pigs now remain (6).

Recommended future actions include establishing a seed bank for the Catalina mahogany to preserve its genetic diversity, and attempting to establish further Catalina mahogany populations, to protect against unpredictable natural events (6). It also needs to be determined whether the seedlings and saplings present in Wild Boar Gully are pure Catalina mahogany individuals, or hybrids (6).

Learn more about the Catalina mahogany:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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    This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact:
    arkive@wildscreen.org.uk

    1. IUCN Red List (February, 2010)
      http://www.iucnredlist.org/
    2. Abrams, A. (1964) Illustrated Flora of the Pacific States. Stanford University Press, California.
    3. Center for Plant Conservation: Conserving and Restoring America's Native Plants (November, 2010)
      http://www.centerforplantconservation.org/
    4. Catalina Island Conservancy - Catalina mahogany trees (November, 2010)
      http://www.catalinaconservancy.org/index.php?s=wildlife&p=catalina_mahogany_trees
    5. McMinn, H. (1951) An Illustrated Manual of California Shrubs. University of California Press, California.
    6. Wallace, G.D. (2007) Cercocarpus traskiae (Catalina Island mountain-mahogany) Five-Year Review: Summary and Evaluation. U.S. Fish and Wildlife Service, U.S. Available at:
      http://ecos.fws.gov/docs/five_year_review/doc1146.pdf
    7. Bonner, F.T. and Karrfalt, R.P. (2008) The Woody Plant Seed Manual. U.S. Department of Agriculture, Forest Service, Washington, DC.
    8. Avise, J.C. and Hamrick, J.L. (1996) Conservation Genetics: Case Histories From Nature. Kluwer Academic Publishers, Massachusetts.