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

flowering A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants (plants of the division Angiospermae). The biological function of a flower is to facilitate reproduction, usually by providing a mechanism ...

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 okra, cotton, cacao and durian. There are also some genera containing familiar ...

, that is

endemic Endemism is the state of a species being found 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 found elsew ...

to the island of

Kauai Kauai, () anglicized as Kauai ( ), is geologically the second-oldest of the main Hawaiian Islands (after Niʻihau). With an area of 562.3 square miles (1,456.4 km2), it is the fourth-largest of these islands and the 21st largest island ...

Hawaii Hawaii ( ; haw, Hawaii or ) is a state in the Western United States, located in the Pacific Ocean about from the U.S. mainland. It is the only U.S. state outside North America, the only state that is an archipelago, and the only stat ...

. 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 Zea ...

''." 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. It is known by the Native Hawaiians as ''hau kuahiwi'' which means "mountain Hibiscus". The Latin name ''Hibiscadelphus'' means "brother of ''Hibiscus''". It is distinc ...

'' 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 (often also called a 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 ...

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, including only woody plants with secondary growth, plants that are ...

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

leaves A leaf (plural, : leaves) is any of the principal appendages of a vascular plant plant stem, stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", wh ...

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 pla ...

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

flower A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants (plants of the division Angiospermae). The biological function of a flower is to facilitate reproduction, usually by providing a mechani ...

s are long and surrounded by triangular

bract In botany, a bract is a modified or specialized leaf, especially one associated with a reproductive structure such as a flower, inflorescence axis or cone scale. Bracts are usually different from foliage leaves. They may be smaller, larger, or of ...

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 The term ''sepalum'' was coined b ...

s form a calyx tube around the greenish yellow

petal Petals are modified Leaf, leaves that surround the reproductive parts of flowers. They are often advertising coloration, brightly colored or unusually shaped to attract pollinators. All of the petals of a flower are collectively known as the ''c ...

s, which turn maroon as they age. The

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

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

seed A seed is an embryonic plant enclosed in a protective outer covering, along with a food reserve. The formation of the seed is a part of the process of reproduction in seed plants, the spermatophytes, including the gymnosperm and angiospe ...

s around long. The capsule dehisces 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 (geology), rock that lies under loose material (regolith) within the crust (geology), crust of Earth or another terrestrial planet. Definition Bedrock is the solid rock that underlies looser surface mater ...

overlain by dry, crumbly red-brown

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

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

tributary A tributary, or affluent, is a stream or river that flows into a larger stream or 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 drain the surrounding drainage ...

Waimea Canyon Waimea Canyon, also known as the Grand Canyon of the Pacific, is a large canyon, approximately ten miles (16 km) long and up to 3,000 feet (900 m) deep, located on the western side of Kauai in the Hawaiian Islands of the United States. ...

, at an elevation of roughly . Mean temperature in this habitat ranges from and average annual rainfall is . Associated plants include kukui (''

Aleurites moluccana ''Aleurites moluccanus'', the candlenut, is a flowering tree in the spurge family, Euphorbiaceae, also known as candleberry, Indian walnut, ''kemiri'', varnish tree, ''nuez de la India'', ''buah keras'', ''godou'', kukui nut tree, and ''rata ke ...

''), āhinahina (''

Artemisia Artemisia may refer to: People * Artemisia I of Caria (fl. 480 BC), queen of Halicarnassus under the First Persian Empire, naval commander during the second Persian invasion of Greece * Artemisia II of Caria (died 350 BC), queen of Caria under th ...

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, ...

''), lama (''

Diospyros sandwicensis ''Diospyros sandwicensis'' is a species of flowering tree in the ebony family, Ebenaceae, that is endemic to Hawaii. It belongs to the same genus as both persimmons and ebony. Its common name, ''lama'', also means enlightenment in Hawaiian. ...

''), 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 con ...

'' spp.), kuluī (''

Nototrichium ''Nototrichium'' is a genus of flowering plants in the family Amaranthaceae. All members of the genus are endemic to the Hawaiian Islands. They are known in Hawaiian as ''kuluī''. Species *''Nototrichium divaricatum'' Lorence (Kauai) *'' Noto ...

sandwicense''), ālaa ('' Pouteria sandwicensis''), Sacramento Bur (''

Triumfetta ''Triumfetta'' is a genus of plants in the 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 okra, cotton, ...

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, are several forms of mass wasting that may include a wide range of ground movements, such as rockfalls, deep-seated grade (slope), slope failures, mudflows, and debris flows. Landslides occur in a variety of ...

. 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 the most powerful hurricane to strike Hawaii in recorded history. Forming on September 5, 1992, during the strong 1990–1995 El Niño, Iniki was one of eleven Centr ...

. 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, an ...

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 Lāwai Bay, in a valley transecte ...

(

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 I ...

) on Kauai and

Waimea Valley Waimea Valley is an area of historic cultural significance on the North Shore of Oahu, Hawaii. The valley, being an important place in Hawaiian religion, includes several historical structures including stone terraces and walls constructed duri ...

Oahu Oahu () (Hawaiian language, Hawaiian: ''Oʻahu'' ()), also known as "The Gathering place#Island of Oʻahu as The Gathering Place, Gathering Place", is the third-largest of the Hawaiian Islands. It is home to roughly one million people—over t ...

. 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 a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed 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 known only by living members kept in captivity or as a naturalized population outside its historic range due ...

(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

* * {{Taxonbar, from=Q1617207 distans Endemic flora of Hawaii Biota of Kauai Trees of Hawaii Plants described in 1973