''Hibiscadelphus distans'' (Kauai hau kuahiwi) is an extremely rare species of

flowering Flowers, also known as blooms and blossoms, are the reproductive structures of flowering plants ( angiosperms). Typically, they are structured in four circular levels, called whorls, around the end of a stalk. These whorls include: calyx, m ...

plant in the mallow family,

Malvaceae Malvaceae (), or the mallows, is a family of flowering plants estimated to contain 244 genera with 4225 known species. Well-known members of economic importance include Theobroma cacao, cacao, Cola (plant), cola, cotton, okra, Hibiscus sabdariffa, ...

, that is

endemic Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...

to the island of

Kauai Kauai (), anglicized as Kauai ( or ), is one of the main Hawaiian Islands. It has an area of 562.3 square miles (1,456.4 km2), making it the fourth-largest of the islands and the 21st-largest island in the United States. Kauai lies 73 m ...

Hawaii Hawaii ( ; ) is an island U.S. state, state of the United States, in the Pacific Ocean about southwest of the U.S. mainland. One of the two Non-contiguous United States, non-contiguous U.S. states (along with Alaska), it is the only sta ...

. It is known as hau kuahiwi in Hawaiian, which means "upland ''

Hibiscus tiliaceus ''Hibiscus tiliaceus'', commonly known as the sea hibiscus or coast cottonwood, is a species of flowering tree in the mallow family, Malvaceae, with a pantropical distribution along coastlines. It has also been introduced to Florida and New Zeal ...

''." It is a bush or small tree with heart-shaped leaves and yellow flowers and grows at between 1,000 and 1,800 feet (300 and 550 m) in the remnants of native dry forests. Despite its rarity, it is believed to be the only surviving species in the genus ''

Hibiscadelphus ''Hibiscadelphus'' is a genus of flowering plants that are endemic to Hawaii, Hawaii. It is known by the Native Hawaiians as ''hau kuahiwi'' which means "mountain Hibiscus". The Latin name ''Hibiscadelphus'' means "brother of ''Hibiscus''". It i ...

'' which is only known from Hawaii, the other five species having recently become extinct in the wild, some being known from only a single plant.

Description

''Hibiscadelphus distans'' is a

shrub A shrub or bush is a small to medium-sized perennial woody plant. Unlike herbaceous plants, shrubs have persistent woody stems above the ground. Shrubs can be either deciduous or evergreen. They are distinguished from trees by their multiple ...

or small

tree In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, e.g., including only woody plants with secondary growth, only ...

up to tall with smooth bark and a rounded crown. The heart-shaped

leaves A leaf (: leaves) is a principal appendage of the stem of a vascular plant, usually borne laterally above ground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, stem, ...

are in length and have rounded serrations on the margins and stellate

trichome Trichomes (; ) are fine outgrowths or appendages on plants, algae, lichens, and certain protists. They are of diverse structure and function. Examples are hairs, glandular hairs, scales, and papillae. A covering of any kind of hair on a plant ...

s (star-shaped hairs) on the upper on lower surfaces. The

flower Flowers, also known as blooms and blossoms, are the reproductive structures of flowering plants ( angiosperms). Typically, they are structured in four circular levels, called whorls, around the end of a stalk. These whorls include: calyx, m ...

s are long and surrounded by triangular

bract In botany, a bract is a modified or specialized leaf, associated with a reproductive structure such as a flower, inflorescence axis or cone scale. Bracts are usually different from foliage leaves in size, color, shape or texture. They also lo ...

s. The

sepal A sepal () is a part of the flower of angiosperms (flowering plants). Usually green, sepals typically function as protection for the flower in bud, and often as support for the petals when in bloom., p. 106 Etymology The term ''sepalum'' ...

s form a calyx tube around the greenish yellow

petal Petals are modified leaves that form an inner whorl surrounding the reproductive parts of flowers. They are often brightly coloured or unusually shaped to attract pollinators. All of the petals of a flower are collectively known as the ''corol ...

s, which turn maroon as they age. The

fruit In botany, a fruit is the seed-bearing structure in flowering plants (angiosperms) that is formed from the ovary after flowering. Fruits are the means by which angiosperms disseminate their seeds. Edible fruits in particular have long propaga ...

is a long, wide capsule that is divided into five sections. Each section contains two

seed In botany, a seed is a plant structure containing an embryo and stored nutrients in a protective coat called a ''testa''. More generally, the term "seed" means anything that can be Sowing, sown, which may include seed and husk or tuber. Seeds ...

s around long. The capsule

dehisces Dehiscence is the splitting of a mature plant structure along a built-in line of weakness to release its contents. This is common among fruits, anthers and sporangia. Sometimes this involves the complete detachment of a part. Structures that op ...

when mature, releasing the seeds.

Habitat

Hau kuahiwi is found within low to mid-elevations, between in highly degraded remnants of native

dry forests The tropical and subtropical dry broadleaf forest is a habitat type defined by the World Wide Fund for Nature and is located at tropical and subtropical latitudes. Though these forests occur in climates that are warm year-round, and may receive ...

. The substrate is

basalt Basalt (; ) is an aphanite, aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the planetary surface, surface of a terrestrial ...

bedrock In geology, bedrock is solid rock that lies under loose material ( regolith) within the crust of Earth or another terrestrial planet. Definition Bedrock is the solid rock that underlies looser surface material. An exposed portion of bed ...

overlain by dry, crumbly red-brown

soil Soil, also commonly referred to as earth, is a mixture of organic matter, minerals, gases, water, and organisms that together support the life of plants and soil organisms. Some scientific definitions distinguish dirt from ''soil'' by re ...

. The current population exists in the Lower Koaie Canyon, a

tributary A tributary, or an ''affluent'', is a stream or river that flows into a larger stream (''main stem'' or ''"parent"''), river, or a lake. A tributary does not flow directly into a sea or ocean. Tributaries, and the main stem river into which they ...

Waimea Canyon Waimea Canyon, also known as the Grand Canyon of the Pacific, is a large canyon, approximately long and up to deep, located on the western side of Kauai in the Hawaiian Islands of the United States. Waimea is Hawaiian for "reddish water", a ...

, at an elevation of roughly . Mean temperature in this habitat ranges from and average annual rainfall is . Associated plants include kukui ('' Aleurites moluccana''), āhinahina ('' Artemisia kauaiensis''), alahee (''

Psydrax odorata ''Psydrax odorata'', known as ''alahee'' in Hawaiian, is a species of flowering shrub or small tree in the coffee family, Rubiaceae. It is native to the Pacific Islands, New Guinea and Australia. Description The species range from in height, h ...

''), lama ('' Diospyros sandwicensis''), nehe (''

Lipochaeta ''Lipochaeta'', common name nehe, is a genus of flowering plants in the family Asteraceae that is endemic to Hawaii. Taxonomy There are difficulties regarding the classification of this genus for its affinities are uncertain. Some studies have ...

connata''), kōlea (''

Myrsine ''Myrsine'' is a genus of flowering plants in the family Primulaceae. It was formerly placed in the family Myrsinaceae before this was merged into the Primulaceae. It is found nearly worldwide, primarily in tropical and subtropical areas. It co ...

'' spp.), kuluī ('' Nototrichium sandwicense''), ālaa (''

Planchonella sandwicensis ''Planchonella sandwicensis'' is a species of flowering tree in the sapodilla family, Sapotaceae, that is endemic to the main islands of Hawaii. Names for this species in the Hawaiian language include ''Ālaa'', ''Āulu'' and ''Ēlaa''. Descrip ...

''), Sacramento Bur (''

Triumfetta ''Triumfetta'' is a genus of plants in the family Malvaceae. Burbark is a common name for plants in this genus. The genus was originally described and published by Carl Linnaeus in his book Sp. Pl. on page 444 in 1753. There are about 176 s ...

semitriloba'') and āulu ('' Sapindus oahuensis'').

Conservation

There are only two known naturally occurring populations of ''H. distans'', both in the Lower Koaie Canyon area, Puu Ka Pele Forest Reserve, with an estimated 20 wild and 150 reintroduced trees. The original population, found in 1972, was located in Koaie Canyon within the State-owned Nā Pali Kona Forest Reserve. In 1989, this population was destroyed by a

landslide Landslides, also known as landslips, rockslips or rockslides, are several forms of mass wasting that may include a wide range of ground movements, such as rockfalls, mudflows, shallow or deep-seated slope failures and debris flows. Landslides ...

. A second population of fifty trees in the Hipalau Valley was destroyed in 1992 by

Hurricane Iniki Hurricane Iniki ( ; Hawaiian: ''iniki'' meaning "strong and piercing wind") was a hurricane that struck the island of Kauai on September 11, 1992. It was the most powerful hurricane to strike Hawaii in recorded history, and the only hurricane to ...

. Two

botanical garden A botanical garden or botanic gardenThe terms ''botanic'' and ''botanical'' and ''garden'' or ''gardens'' are used more-or-less interchangeably, although the word ''botanic'' is generally reserved for the earlier, more traditional gardens. is ...

s in Hawaii have cultivated this plant species:

McBryde Garden McBryde Garden (approx. ) is a botanical garden located on the south shore of Kauai, Hawaii. It is one of five gardens of the non-profit National Tropical Botanical Garden (NTBG). The garden is situated above Lāwaʻi, Lāwai Bay, in a valley ...

(

National Tropical Botanical Garden The National Tropical Botanical Garden (NTBG) is a Hawaii-based not-for-profit institution dedicated to tropical plant research, conservation, and education. It operates a network of botanical gardens and preserves in Hawaii and Florida. History ...

) on Kauai and Waimea Valley on

Oahu Oahu (, , sometimes written Oahu) is the third-largest and most populated island of the Hawaiian Islands and of the U.S. state of Hawaii. The state capital, Honolulu, is on Oahu's southeast coast. The island of Oahu and the uninhabited Northwe ...

. Despite the extreme rarity of ''H. distans'', it actually has the largest wild population of any ''

'' species. Five of the other six species are

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

extinct in the wild A species that is extinct in the wild (EW) is one that has been categorized by the International Union for Conservation of Nature as only consisting of living members kept in captivity or as a naturalized population outside its historic range ...

(four were only ever known from a single wild tree), the exception being ''H. woodii'' (also from Kauai), which is known from only four individuals.

References

External links

* * {{Authority control distans Endemic flora of Hawaii Biota of Kauai Trees of Hawaii Plants described in 1973