Hibiscadelphus
Encyclopedia
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". It is distinctive for its peculiar flowers, which do not fully open.
Hibiscadelphus was first described by Austrian-American botanist Joseph Rock
in 1911 on the basis of the species H. giffardianus. The genus consists of seven species, one of which, H. woodii, was only described in 1995. They are large shrubs or trees, up to 7 metres (23 ft) tall, with nearly circular leaves. It is characterized by flowers that never open to the flat form of Hibiscus
, but remain folded together in a tubular form. This is presumed to be an adaptation to pollination by honeycreepers
. The fruits are rough capsules containing up to 15 hairy seeds.
The lateness of its discovery by western botanists indicates that Hibiscadelphus was already rare by the time Europeans arrived in Hawaii. Four species - H. bombycinus, H. crucibracteatus, H. giffardianus, and H. wilderianus - were only ever known from a single individual in the wild. Today, three of the seven species are extinct and all of the remainder are either extinct in the wild or extremely rare. Although it has been suggested that poor pollination due to extinction of their honeycreeper pollinators is a factor, the abundant fruits and high germination rates of at least some species argues against this. The main reason is probably feeding on seeds by rats. This fits with a decline of the group that began long before the arrival of cat
s, mosquito
es, and avian malaria
decimated honeycreeper populations, since the Polynesian rat
arrived with the early Hawaiian settlers. The widespread destruction of dry forests
, both before and after European contact, was also a major factor.
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...
from the subfamily Malvoideae
Malvoideae
Malvoideae is a botanical name at the rank of subfamily, which includes in the minimum the genus Malva. It was first used by Burnett in 1835, but was not much used until recently, where, within the framework of the APG System, which unites the families Malvaceae, Bombacaceae, Sterculiaceae and...
endemic to 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 was known by the Native Hawaiians
Native Hawaiians
Native Hawaiians refers to the indigenous Polynesian people of the Hawaiian Islands or their descendants. Native Hawaiians trace their ancestry back to the original Polynesian settlers of Hawaii.According to the U.S...
as hau kuahiwi which means "mountain Hibiscus". The Latin name means "brother of Hibiscus". It is distinctive for its peculiar flowers, which do not fully open.
Description
Joseph Rock
Joseph Francis Charles Rock was an Austrian-American explorer, geographer, linguist and botanist.-Life:He was born in Vienna, Austria, but emigrated to the United States in 1905 and moved to Honolulu, Hawaii in 1907, where he eventually became an authority on the flora there...
in 1911 on the basis of the species H. giffardianus. The genus consists of seven species, one of which, H. woodii, was only described in 1995. They are large shrubs or trees, up to 7 metres (23 ft) tall, with nearly circular leaves. It is characterized by flowers that never open to the flat form of Hibiscus
Hibiscus
Hibiscus is a genus of flowering plants in the mallow family, Malvaceae. It is quite large, containing several hundred species that are native to warm-temperate, subtropical and tropical regions throughout the world...
, but remain folded together in a tubular form. This is presumed to be an adaptation to pollination by honeycreepers
Hawaiian honeycreeper
Hawaiian honeycreepers are small, passerine birds endemic to Hawaii. Some authorities still categorize this group as a family Drepanididae, but in recent years, most authorities consider them a subfamily, Drepanidinae, of Fringillidae, the finch family...
. The fruits are rough capsules containing up to 15 hairy seeds.
The lateness of its discovery by western botanists indicates that Hibiscadelphus was already rare by the time Europeans arrived in Hawaii. Four species - H. bombycinus, H. crucibracteatus, H. giffardianus, and H. wilderianus - were only ever known from a single individual in the wild. Today, three of the seven species are extinct and all of the remainder are either extinct in the wild or extremely rare. Although it has been suggested that poor pollination due to extinction of their honeycreeper pollinators is a factor, the abundant fruits and high germination rates of at least some species argues against this. The main reason is probably feeding on seeds by rats. This fits with a decline of the group that began long before the arrival of cat
Cat
The cat , also known as the domestic cat or housecat to distinguish it from other felids and felines, is a small, usually furry, domesticated, carnivorous mammal that is valued by humans for its companionship and for its ability to hunt vermin and household pests...
s, mosquito
Mosquito
Mosquitoes are members of a family of nematocerid flies: the Culicidae . The word Mosquito is from the Spanish and Portuguese for little fly...
es, and avian malaria
Avian malaria
Avian malaria is a parasitic disease of birds.-Etiology:Avian malaria is most notably caused by Plasmodium relictum, a protist that infects birds in tropical regions...
decimated honeycreeper populations, since the Polynesian rat
Polynesian Rat
The Polynesian Rat, or Pacific Rat , known to the Māori as kiore, is the third most widespread species of rat in the world behind the Brown Rat and Black Rat. The Polynesian Rat originates in Southeast Asia but, like its cousins, has become well travelled – infiltrating Fiji and most Polynesian...
arrived with the early Hawaiian settlers. The widespread destruction of 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...
, both before and after European contact, was also a major factor.
Hibiscadelphus species
- Hibiscadelphus bombycinusHibiscadelphus bombycinusThe Kawaihae Hibiscadelphus was a species of flowering plant in the Malvaceae family. It was found only in Hawaii. It has not been collected since 1868.-Source:...
† - Known from only one collection, before 1868, from KawaihaeKawaihaeKawaihae is an unincorporated community on the west side of the island of Hawaii in the U.S. state of Hawaii, north of Kailua-Kona. Its harbor includes a fuel depot, shipping terminal and military landing site. Outside of the man-made breakwall of the harbor is a popular surf spot and the Pua...
, Hawaii. - Hibiscadelphus crucibracteatusHibiscadelphus crucibracteatusHibiscadelphus crucibracteatus was a species of flowering plant in the Malvaceae family. It was found only in Hawaii.It was discovered in 1981 and the single known specimen has since died.-Source:...
† - In 1981 a single tree was discovered on the slopes of the Puhielelu Ridge on LānaiLanaiLānai or Lanai is the sixth-largest of the Hawaiian Islands. It is also known as the Pineapple Island because of its past as an island-wide pineapple plantation. The only town is Lānai City, a small settlement....
at an altitude of 750 metres (2,460.6 ft). This tree died in 1985. Efforts to save the species failed because seeds did not germinate. - Hibiscadelphus distansHibiscadelphus distansHibiscadelphus distans is an extremely rare species of flowering tree in the mallow family, Malvaceae, that is endemic to the island of Kauai in Hawaii. It is known as hau kuahiwi in Hawaiian, which means "upland Hibiscus tiliaceus."...
- Less than 200 wild individuals occur above the Koaie River on KauaiKauaiKauai 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",...
, but it sets abundant, fertile seeds in cultivation. - Hibiscadelphus giffardianusHibiscadelphus giffardianusHibiscadelphus giffardianus is a species of flowering plant in the mallow family, Malvaceae, that is endemic to the Big Island of Hawaii. It is believed to be extinct in the wild; any remaining plants are threatened by habitat loss. Cultivated plants exist in Hawaii Volcanoes National Park. It...
- In 1910 Joseph RockJoseph RockJoseph Francis Charles Rock was an Austrian-American explorer, geographer, linguist and botanist.-Life:He was born in Vienna, Austria, but emigrated to the United States in 1905 and moved to Honolulu, Hawaii in 1907, where he eventually became an authority on the flora there...
discovered a single tree at Kīpuka Puaulu, now part of Hawaii Volcanoes National ParkHawaii Volcanoes National ParkHawaii Volcanoes National Park, established in 1916, is a United States National Park located in the U.S. State of Hawaii on the island of Hawaii. It encompasses two active volcanoes: Kīlauea, one of the world's most active volcanoes, and Mauna Loa, the world's most massive volcano...
. This tree died in 1930, but cuttings were saved. Several hundred individuals have since been planted in the park, but no natural regeneration has been observed and few trees produce viable seeds. - Hibiscadelphus hualalaiensisHibiscadelphus hualalaiensisHibiscadelphus hualalaiensis is a species of flowering plant in the mallow family, Malvaceae, that is endemic to the Big Island of Hawaii. The last known plant died in 1992, making it most likely extinct in the wild; any remaining plants are threatened by habitat loss. It inhabits dry and mixed...
- This species formerly occurred in North Kona. The last wild tree died in 1992, but it survives in cultivation and trees have been outplanted in forest reserves. - Hibiscadelphus wilderianusHibiscadelphus wilderianusHibiscadelphus wilderianus was a species of flowering plant in the Malvaceae family.It was found only in Hawaii. The species was known from a single specimen discovered on Maui in 1910. Today it is believed to be extinct.-Source:...
† - Possibly extinct around 1912. Only known from a single tree which was discovered at Auwahi on MauiMauiThe island of Maui is the second-largest of the Hawaiian Islands at and is the 17th largest island in the United States. Maui is part of the state of Hawaii and is the largest of Maui County's four islands, bigger than Lānai, Kahoolawe, and Molokai. In 2010, Maui had a population of 144,444,...
. - Hibiscadelphus woodiiHibiscadelphus woodiiHibiscadelphus 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....
- This species was discovered in 1991, on Kauai. Only four individuals are known. - Hibiscadelphus x puakuahiwi - A hybrid between H. giffardianus and H. hualalaiensis. In the 1960s both species were planted on Mauna LoaMauna LoaMauna Loa is one of five volcanoes that form the Island of Hawaii in the U.S. state of Hawaii in the Pacific Ocean, and the largest on Earth in terms of volume and area covered. It is an active shield volcano, with a volume estimated at approximately , although its peak is about lower than that...
in Hawaii Volcanoes National Park, where only the former occurred naturally. The two cross-pollinated, and the hybrid seeds were unknowingly collected and planted. When discovered in 1973 the hybrids and H. hualalaiensis trees were cut down, although at least one hybrid remains as of 2011.