Pua’ala (Brighamia rockii)

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Pua’ala
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Pua’ala fact file

Pua’ala description

KingdomPlantae
PhylumTracheophyta
ClassMagnoliopsida
OrderCampanulales
FamilyCampanulaceae
GenusBrighamia (1)

The Pua’ala is one of two endangered Brighamia species endemic to Hawaii, the ‘olulu (B. insignis) and the pua’ala (B. rockii). These species are morphologically similar and considered amongst the most unusual of Hawaiian flora (3). A distinguishing feature is their tall succulent, usually un-branched stem, bulbous at the base and tapering towards the apex. The stem is crowned in a rosette of fleshy leaves and the fragrant flowers are trumpet-shaped (4). The flowers of pua’ala are white while those of the ‘olulu (B. insignis) are cream to yellow. During its juvenile stage the pua’ala has a distinctive purple stem, unlike the ‘olulu (B. insignis) (5).

Also known as
‘olulu, alula, haha, pu aupaka.
Synonyms
Brighamia remyi, Brighamia rockii longiloba.
Size
Height: 1 – 5 m (1)
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Pua’ala biology

A perennial, succulent plant adapted to tolerate the salty environment of exposed sea-cliffs (3). Pua’ala blooms in the autumn (6). The fruit produced is a green capsule containing 20 to 60 seeds, which ripens six to eight weeks after pollination. Only 5% of the flowers produce pollen, and very few fruits are formed per inflorescence (5). The unusually low rate of fruit production is thought to be as a consequence of the presumed extinction of the pua’ala’s natural pollinator, believed to be a species of moth (6).

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Pua’ala range

Endemic to the Island of Molokai and historically on Maui and Lanai, the pua’ala exists in three sub-populations totalling less than 50 mature individuals (1).

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Pua’ala habitat

The pua’ala is found on exposed steep coastal cliffs with native grasses, shrubs, and trees (1), from sea level to 470 meters elevation (5).

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Pua’ala status

Classified as Critically Endangered (CR - D) on the IUCN Red List 2004 (1). Listed as an endangered, endemic species under the U.S. Endangered Species Act 1992 (2).

IUCN Red List species status – Critically Endangered

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Pua’ala threats

Once fairly common, the pua’ala is now at risk of extinction due to habitat degradation, predation by feral goats, and competition from introduced plant and animal species (4). Low reproductive rates, which exacerbate the problem by making recovery slow, could be due to low pollen production, low establishment of seedlings, and the decline of natural pollinators (5). An additional fear is low genetic variability, as a result of inbreeding between the few remaining plants, will mean failure to produce healthy seedlings able of responding to environmental change (4).

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Pua’ala conservation

The Conservation Department of the National Tropical Botanical Garden (NTBG) in Hawaii has taken a lead in the conservation of this rare and unusual species by conducting manual pollination and seed collection. As a result, cultivated conservation collections have been established, which will ensure against total extinction. Recovery plans are being created that will investigate possible alternative pollinators and create guidelines for the reintroduction of the pua’ala (4). It has been suggested that a successful recovery plan needs to examine the whole of the reproductive strategy and also map the genetic diversity in the surviving populations. Research into possible pests and diseases and testing the influence of weeding and fencing has also been advocated (5).

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Find out more

For more information on the pua’ala, see:

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Authentication

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

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Glossary

Endemic
A species or taxonomic group that is only found in one particular country or geographic area.
Inflorescence
The reproductive shoot of the plant that bears flowers.
Perennial
Plants that live for at least three seasons; after an initial period they produce flowers once a year.
Succulent
In plants, species with thick fleshy water storing stems and leaves.
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References

  1. IUCN Red List of Threatened Species (October, 2005)
    http://www.redlist.org
  2. Natureserve Explorer (October, 2005)
    http://www.natureserve.org/explorer
  3. Gemmill, C.E.C., Ranker, T.A., Ragone, D., Perlman, S.P. and Wood, K.R. (1998) Conservation Genetics of the Endangered Endemic Hawaiian Genus Brighamia (Campanulaceae). American Journal of Botany, 85(4): 528 - 539. Available at:
    http://www.amjbot.org/cgi/reprint/85/4/528
  4. National Tropical Botanical Garden (NTBG): The Brighamia of Hawaii. (October, 2005)
    http://www.wildlifebiz.org
  5. Center for Plant Conservation – CPC National Collection Plant Profile (October, 2005)
    http://www.centerforplantconservation.org
  6. The University of Hawaii - Hawaiian Native Plant Propagation Database (October, 2005)
    http://www2.hawaii.edu/~eherring/hawnprop/bri-insi.htm
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Image credit

Pua’ala  
Pua’ala

© Hank Oppenheimer/ Plant Extinction Prevention Program

Hank Oppenheimer
hmo3500@earthlink.net

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