Kauila (Alphitonia ponderosa)

KingdomPlantae
PhylumTracheophyta
ClassMagnoliopsida
OrderRhamnales
FamilyRhamnaceae
GenusAlphitonia (1)
SizeHeight: 15 - 24 m (2)
Trunk diameter: 0.2 - 0.6 m (2)
Leaf length: 5 -15 cm (2)
Flower width: c. 6mm (2)

The Kauila is classified as Vulnerable (VU) on the IUCN Red List (1).

The wood of the kauila (Alphitonia ponderosa) tree is greatly treasured by the indigenous Hawaiian population, both for its attractive appearance and for its physical and practical properties. This species has strong and extremely hard wood (3), which is dense enough to sink in water (2). The dark red or cherry-coloured heartwood of the kauila can be streaked with black, and is found beneath a wide ring of light brown to yellow sapwood and a rough, whitish-grey coloured bark (2).

The kauila's leaves are long and ovulate in shape, with a shiny green surface and a light green underside, where the prominent and rust-coloured leaf veins can be found (2). Flowers emerge from furry buds, formed by miniature leaves, in a cluster at the end of widely forking, hairy stems. The small green flowers can be one or both sexes, with cuplike petals in the arrangement of a five-pointed star (3).

The fruit, or drupes, appear in the form of woody capsules (3), with each containing 2 or 3 seeds and measuring approximately 15 millimetres in diameter. The seeds themselves are shiny and oblong shaped, with a thick red covering (2). 

The kauila is confined to the six Hawaiian islands: Hawaii, Maui, Molokai, Lanai, Oahu and Kauai. It is cited as being rare on all of these islands except Kauai (1).

The kauila is found primarily in dry to moderately moist (mesic) woodlands (3) between elevations of 240 and 1,250 metres (4). It also exists as a shrub on exposed ridges (2).

The kauila is a long-living perennial plant that is poorly described. However, it has been suggested that there is a geographic restriction on pollen dispersal between individuals. The plant is believed to be insect pollinated, a trait typical of members of the buckthorn family (Rhamnaceae) (3).

No local, living bird species appear to be able to open the hard kauila fruits; however, it has been proposed that larger bird species that are now extinct may have aided in seed dispersal in the past (3). Other species in the Alphitonia genus are said to be slow growing and shade tolerant (5).

The dense, hard kaulia wood can be used as a substitute for metal, making it important to the local Hawaiian economy (3). It is also used in the creation of spears, fishing hooks, and jewellery such as hair pins and pendants (2). 

The two main threats to the kauila are the damage caused by the introduction of invasive species (1) and the loss of its dry land forest habitat (6).

The introduction of non-native plant species to Hawaii has lead to the drastic alteration of the kauila’s dry land forest habitat. Large amounts of the original forest understory have become covered in a blanket of Kikuyu grass (Pennisetum clandestinum), a plant native to East Africa but an aggressive weed in Hawaii. Kikuyu grass overcrowds and suppresses the seedlings of other species, preventing their growth. The introduction of this grass, originally for the purpose of grazing cattle, has turned what was once a fertile breeding ground for most Hawaiian dry land trees into a 'museum forest' containing only mature specimens, where no saplings have been able to grow for fifty years (7).

Introduced grazing species such as pigs and deer have also threatened the potential of kauila sapling growth, while invasive rat populations, which feed on kauila seeds, have further limited this species’ ability to propagate (1).

The overall kauila population is also under threat from reduced genetic diversity, caused by severe habitat loss and fragmentation due to urban and agricultural development (3). As a result of this human disturbance and the damage caused by invasive species, it has been estimated that over 90 percent of the kauila's primary dry forest habitat has been lost (3). This has led to the kauila population being severely fragmented across a poorer quality habitat, with a reduced growth range and an estimated extent of occurrence less than 20,000 square kilometres (1). On all islands except Kauai, fewer than 50 individuals were observed in 1988, according to the Hawaii Heritage Program (3).

The kauila has been recognised as a 'species of concern' due to the low numbers observed by the Hawaii Heritage Program (3). Local state regulation has been put in place to encourage the protection of many of Hawaii’s native plant species, including the kauila, and to raise public awareness about the threats that they face. Surveys have shown most landscape architects are now planting native Hawaiian plants instead of imported species as a result of this legislation (6).

Find out more about conservation in Hawaii:

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 (November, 2011)
    http://www.iucnredlist.org/
  2. Little Jr., E.L. and Skolmen, R.G. (1989) Common Forest Trees of Hawaii (Native and Introduced). In: Agriculture Handbook No. 679. USDA Forest Service, Washington D.C.
  3. Kwon, J.A. and Morden, C.W. (2002) Population genetic structure of two rare tree species (Colubrina oppositifolia and Alphitonia ponderosa, Rhamnaceae) from Hawaiian dry and mesic forests using random amplified polymorphic DNA markers. Molecular Ecology, 11(6): 991-1001.
  4. Bishop Museum (November, 2011)
    http://data.bishopmuseum.org/ethnobotanydb/ethnobotany.php?b=d&ID=kauila_A
  5. Jackson, R.V. and Bach, C.E. (1999) Effects of herbivory on growth and survival of seedlings of a rainforest tree, Alphitonia whitei (Rhamnaceae). Australian Journal of Ecology, 24(3): 278-286.
  6. Tamimi, L.N. (1999) The Use of Native Hawaiian Plants by Landscape Architects in Hawaii. M.A. Thesis, Virginia Polytechnic Institute and State University, Virginia.
  7. Medeiros, A.C. (2003) Maui Kumu Keli‘I Tau‘a Welcomes Hawaiian seedlings back to Auwahi. Native Plants, 4: 448-51.