Hibiscadelphus distans is an extremely rare species of flowering

Flowering plant

The flowering plants , also known as Angiospermae or Magnoliophyta, are the most diverse group of land plants. Angiosperms are seed-producing plants like the gymnosperms and can be distinguished from the gymnosperms by a series of synapomorphies...

 tree in the mallow

Malva

Malva is a genus of about 25–30 species of herbaceous annual, biennial, and perennial plants in the family Malvaceae , one of several closely related genera in the family to bear the common English name mallow. The genus is widespread throughout the temperate, subtropical and tropical regions of...

 family, Malvaceae

Malvaceae

Malvaceae, or the mallow family, is a family of flowering plants containing over 200 genera with close to 2,300 species. Judd & al. Well known members of this family include okra, jute and cacao...

, that is endemic to the island of Kauai

Kauai

Kauai or Kauai, known as Tauai in the ancient Kaua'i dialect, is geologically the oldest of the main Hawaiian Islands. With an area of , it is the fourth largest of the main islands in the Hawaiian archipelago, and the 21st largest island in the United States. Known also as the "Garden Isle",...

 in Hawaii

Hawaii

Hawaii is the newest of the 50 U.S. states , and is the only U.S. state made up entirely of islands. It is the northernmost island group in Polynesia, occupying most of an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of...

. It is known as hau kuahiwi in Hawaiian

Hawaiian language

The Hawaiian language is a Polynesian language that takes its name from Hawaii, the largest island in the tropical North Pacific archipelago where it developed. Hawaiian, along with English, is an official language of the state of Hawaii...

, which means "upland Hibiscus tiliaceus."

Description

H. distans is a shrub

Shrub

A shrub or bush is distinguished from a tree by its multiple stems and shorter height, usually under 5–6 m tall. A large number of plants may become either shrubs or trees, depending on the growing conditions they experience...

 or small tree

Tree

A tree is a perennial woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or trunk with clear apical dominance. A minimum height specification at maturity is cited by some authors, varying from 3 m to...

 up to 5 m (16.4 ft) tall with smooth bark and a rounded crown. The heart-shaped leaves

Leaf

A leaf is an organ of a vascular plant, as defined in botanical terms, and in particular in plant morphology. Foliage is a mass noun that refers to leaves as a feature of plants....

 are 4–10 cm (1.6–3.9 in) in length and have rounded serrations on the margins and stellate trichome

Trichome

Trichomes are fine outgrowths or appendages on plants and certain protists. These are of diverse structure and function. Examples are hairs, glandular hairs, scales, and papillae.- Algal trichomes :...

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

Flower

A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants . The biological function of a flower is to effect reproduction, usually by providing a mechanism for the union of sperm with eggs...

s are 3–4 cm (1.2–1.6 in) long and surrounded by triangular bract

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 often different from foliage leaves. They may be smaller, larger, or of a different color, shape, or texture...

s. The sepal

Sepal

A sepal is a part of the flower of angiosperms . Collectively the sepals form the calyx, which is the outermost whorl of parts that form a flower. Usually green, sepals have the typical function of protecting the petals when the flower is in bud...

s form a calyx tube around the greenish yellow petal

Petal

Petals are modified leaves that surround the reproductive parts of flowers. They often are brightly colored or unusually shaped to attract pollinators. Together, all of the petals of a flower are called a corolla. Petals are usually accompanied by another set of special leaves called sepals lying...

s, which turn maroon as they age. The fruit

Fruit

In broad terms, a fruit is a structure of a plant that contains its seeds.The term has different meanings dependent on context. In non-technical usage, such as food preparation, fruit normally means the fleshy seed-associated structures of certain plants that are sweet and edible in the raw state,...

 is a 2.5 cm (0.984251968503937 in) long, 1.5 cm (0.590551181102362 in) wide capsule

Capsule (fruit)

In botany a capsule is a type of simple, dry fruit produced by many species of flowering plants. A capsule is a structure composed of two or more carpels that in most cases is dehiscent, i.e. at maturity, it splits apart to release the seeds within. A few capsules are indehiscent, for example...

 that is divided into five sections. Each section contains two seed

Seed

A seed is a small embryonic plant enclosed in a covering called the seed coat, usually with some stored food. It is the product of the ripened ovule of gymnosperm and angiosperm plants which occurs after fertilization and some growth within the mother plant...

s around 5 mm (0.196850393700787 in) long. The capsule dehisces

Dehiscence (botany)

Dehiscence is the opening, at maturity, in a pre-defined way, of a plant structure, such as a fruit, anther, or sporangium, to release its contents. Sometimes this involves the complete detachment of a part. Structures that open in this way are said to be dehiscent...

 when mature, releasing

Seed dispersal

Seed dispersal is the movement or transport of seeds away from the parent plant. Plants have limited mobility and consequently rely upon a variety of dispersal vectors to transport their propagules, including both abiotic and biotic vectors. Seeds can be dispersed away from the parent plant...

 the seeds.

Habitat

Hau kuahiwi is found within low to mid-elevations, between 1000 and 1800 ft (304.8 and 548.6 m) in highly degraded remnants of native dry forests

Hawaiian tropical dry forests

The Hawaiian tropical dry forests are a tropical dry broadleaf forest ecoregion in the Hawaiian Islands. They cover an area of on the leeward side of the main islands and the summits of Niihau and Kahoolawe. These forests are either seasonal or sclerophyllous. Annual rainfall is less than and...

. The substrate is basalt

Basalt

Basalt is a common extrusive volcanic rock. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Unweathered basalt is black or grey...

ic bedrock

Bedrock

In stratigraphy, bedrock is the native consolidated rock underlying the surface of a terrestrial planet, usually the Earth. Above the bedrock is usually an area of broken and weathered unconsolidated rock in the basal subsoil...

 overlain by dry, crumbly red-brown soil

Soil

Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...

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

Tributary

A tributary or affluent is a stream or river that flows into a main stem river or a lake. A tributary does not flow directly into a sea or ocean...

 of Waimea Canyon

Waimea Canyon State Park

Waimea Canyon, also known as the Grand Canyon of the Pacific, is a large canyon, approximately ten miles long and up to 3,000 feet deep, located on the western side of Kauai in the Hawaiian Islands. Waimea is Hawaiian for "reddish water," a reference to the erosion of the canyon's red soil...

, at an elevation of roughly 350 m (1,148.3 ft). Mean temperature in this habitat ranges from 18.5 to 25.7 °C (65.3 to 78.3 F) and average annual rainfall is 150 cm (59.1 in). Associated plants include kukui (Aleurites moluccana

Candlenut

Aleurites moluccana, 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 or Kukui nut tree....

), āhinahina (Artemisia kauaiensis), alahee (Psydrax odorata

Psydrax odorata

Psydrax odorata, known as Alahee in Hawaiian, is a species of flowering shrub or small tree in the coffee family, Rubiaceae, that is native to the Pacific Islands, Malesia and Australasia...

), lama (Diospyros sandwicensis

Diospyros sandwicensis

Diospyros sandwicensis is a species of flowering tree in the ebony family, Ebenaceae, that is endemic to Hawaii. Its common name, Lama, also means enlightenment in Hawaiian. Lama is a small to medium-sized tree, with a height of and a trunk diameter of . It can be found in dry, coastal mesic,...

), nehe (Lipochaeta

Lipochaeta

Lipochaeta is a genus of flowering plants in the daisy family, Asteraceae.-Selected species:*Lipochaeta connata DC. – Nehe *Lipochaeta degeneri Sherff – Molokai Nehe...

 connata), kōlea (Myrsine

Myrsine

Myrsine is a genus of flowering plants, the nominate genus of the family Myrsinaceae. It is found nearly worldwide, primarily in tropical and subtropical areas...

spp.), kuluī (Nototrichium

Nototrichium

Nototrichium is a genus of flowering plants in the pigweed family, Amaranthaceae. All members of the genus are endemic to the Hawaiian Islands. They are known in Hawaiian as kuluī.-Species:*Nototrichium divaricatum Lorence...

 sandwicense), ālaa (Pouteria sandwicensis

Pouteria sandwicensis

Pouteria 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....

), Sacramento Bur (Triumfetta

Triumfetta

Triumfetta is a genus of plants in the family Malvaceae.There are about 70 species which are widespread across tropical regions. These include :*Triumfetta albida Halford*Triumfetta antrorsa Halford...

 semitriloba) and āulu (Sapindus oahuensis

Sapindus oahuensis

Sapindus oahuensis, commonly known as Āulu or Lonomea, is a species of soapberry that is endemic to Hawaii. It can be found in dry, coastal mesic, and mixed mesic forests at elevations of on the islands of Kauai and Oahu . Āulu reaches a height of and a trunk diameter of...

).

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

Landslide

A landslide or landslip is a geological phenomenon which includes a wide range of ground movement, such as rockfalls, deep failure of slopes and shallow debris flows, which can occur in offshore, coastal and onshore environments...

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

Hurricane Iniki

Hurricane Iniki was the most powerful hurricane to strike the U.S. state of Hawaii in recorded history. Forming on September 5 during the strong El Niño of 1991–1994, Iniki was one of eleven Central Pacific tropical cyclones during the 1992 season. It attained tropical storm status on...

. Two botanical garden

Botanical garden

A botanical garden The 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 a well-tended area displaying a wide range of plants labelled with their botanical names...

s in Hawaii have cultivated this plant species: McBryde Garden

McBryde Garden

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 .The garden is situated above Lāwai Bay, in a valley transected by the Lāwai Stream...

 (National Tropical Botanical Garden

National Tropical Botanical Garden

The National Tropical Botanical Garden is a group that sponors preservation of plants native to the tropics in a network of botanical gardens and preserves.-History:...

) on Kauai and Waimea Valley on Oahu

Oahu

Oahu or Oahu , known as "The Gathering Place", is the third largest of the Hawaiian Islands and most populous of the islands in the U.S. state of Hawaii. The state capital Honolulu is located on the southeast coast...

.

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

Hibiscadelphus

Hibiscadelphus is a genus of Malvaceae from the subfamily Malvoideae endemic to Hawaii. It was known by the Native Hawaiians as hau kuahiwi which means "mountain Hibiscus". The Latin name means "brother of Hibiscus"...

species. Five of the other six species are extinct or extinct in the wild

Extinct in the Wild

Extinct in the Wild is a conservation status assigned to species or lower taxa, the only known living members of which are being kept in captivity or as a naturalized population outside its historic range.-Examples:...

 (four were only ever known from a single wild tree), the exception being H. woodii

Hibiscadelphus woodii

Hibiscadelphus woodii is a species of flowering plant in the mallow family, Malvaceae, that is endemic to Kauai, Hawaii. It is a small tree, reaching a height of .It was discovered in 1991 and described as a new species in 1995....

(also from Kauai), which is known from only four individuals.

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