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The Recovery Plan
for the Gouania hillebrandii
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Gouania
hillebrandii is
a shrub that grows up to 6 feet (2 meters), often comprised of a
single unbranched or sparingly branched stem when less than 2 feet
but becoming more branched and rounded with increased height.
There is distinct variation between the Maui and Moloka`i plants
that may be considered different forms. The West Maui form is an
upright, erect woody shrub with compact leaves. In contrast, the
Moloka`i plants have widely or loosely spreading leaves. They grow
more prostrate and vine-like along the ground, weakly climbing on
other vegetation. Both forms have small white flowers. |
Habitat
& Distribution:
G. hillebrandii
occurs in lowland dry shrubland habitat on leeward slopes of the West
Maui mountains and in lowland mesic forest habitat on East Moloka`i. Population
estimates total 1,700 to 2,100 individuals. The West Maui lowland dry
shrubland habitat where
G. hillebrandii
occurs is one of the best remnants of this habitat type in the Hawaiian
Islands and represents a mosaic of native shrubs such as a`ali`i
(Dodonaea
viscosa)
and pukiawe
(Styphelia tameiameiae)
and native
grasses such as kewelu (Eragrostis sp.)
and pili (Heteropogon contortus).
An equally unique lowland mesic forest patch exists on Moloka`i consisting
of G. hillebrandii, halapepe (Pleomele
auwahiensis),
lama (Diospyros
sandwicensis),
Neraudia
sericea,
the endangered Zanthoxylum hawaiiense,
and kulu`i (Nototrichium
sandwicense)
as well as many other common native shrubs and herbs.
On Maui, located
above Lahaina on the west facing slopes forming the south wall of Kahana
Stream between 1,100 and 1,600 feet (335 and 487 meters), this subpopulation
occupies roughly 15 acres within a designated critical habitat of about
50 acres on three ridges of weathered trachyte lava.
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habitat is land designated and protected by the Federal government
for certain endangered species. The Lihau subpopulation is on State
lands managed by the State
of Hawai`i Department of Land and Natural Resources.
It occurs on roughly 10 acres within a designated critical habitat
of about 60 acres on the west facing foothills at Lihau, between
800 and 1,700 feet (243 and 518 meters) in elevation.
On Moloka`i, there are two small populations consisting of just
a few plants each located just below Pu`u Kolekole on private land.
Several valleys form below Pu`u Kolekole at an elevation of approximately
3,000 feet (910 meters), where each population may be found on the
valley walls in separate drainages. No critical habitat has been
designated for the Moloka`i populations.
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Recovery:
Cattle browsing
and trampling, alien plants Pinnaspis
strachni (Hibiscus
Snow Scale) and Grevillea robusta, leaf-chewing insects; and brush
fire are threats to G. hillerbrandii.. These
plant populations exist in areas that are remote and difficult to access,
thus there have been few in situ conservation efforts for this species.
However, staff from the National Tropical
Botanical Garden are planning to study the variation among the Moloka`i
and West Maui plants to see if they represent truly different varieties.
Collections could be grown in cultivation to serve as experimental material
and for seed production to augment wild populations.
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