Wilkesia hobdyi
Encyclopedia
Wilkesia hobdyi is a species of flowering plant
in the sunflower
family, Asteraceae
, that is endemic to the island of Kauai
in Hawaii
. It was first collected in 1968, and was not formally described until 1971. The number of living plants is estimated at fewer than 300. It is considered Critically Imperiled in global rank which means it is at very high risk of extinction. It has been a federally protected species since 1992. The Wilkesia genus is one of three genera constituting the silversword alliance
, a group of highly diverse yet genetically exceedingly closely related species, all thought to be descended from a colonizing ancestor related to the tarweed of North America.
shrub
with branches reaching a length of 60 cm (23.6 in) extending vertically from the base. Branch tips yield whorl, rather than spirals, of narrow, flat, grass-like, somewhat thick leaves
around 7.5–15 cm (3–5.9 in) long. Cream-colored flower
s are produced in inflorescence
s 2 cm (0.78740157480315 in) in diameter. Flowering has been observed most often in the winter months, but
also during June. This species is probably pollinated through outcrossing and is probably self-incompatible. Insects are the most likely pollinators. Wilkesia die after flowering.
pings in the western part of the island at elevations of 275–400 m (902.2–1,312.3 ft). Rainfall in these sites is less than 1,200 ml per year.
), nehe (Lipochaeta
connata), Lobelia niihauensis, makou (Peucedanum
sandwicense
), kokio ula (Hibiscus kokio
), alahee (Psydrax odorata
), alaala wai nui (Peperomia
spp.), naio (Myoporum sandwicense
), ilima (Sida fallax
), uhaloa (Waltheria indica
), aalii (Dodonaea viscosa
), and kāwelu (Eragrostis variabilis).
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...
in the sunflower
Sunflower
Sunflower is an annual plant native to the Americas. It possesses a large inflorescence . The sunflower got its name from its huge, fiery blooms, whose shape and image is often used to depict the sun. The sunflower has a rough, hairy stem, broad, coarsely toothed, rough leaves and circular heads...
family, Asteraceae
Asteraceae
The Asteraceae or Compositae , is an exceedingly large and widespread family of vascular plants. The group has more than 22,750 currently accepted species, spread across 1620 genera and 12 subfamilies...
, 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 was first collected in 1968, and was not formally described until 1971. The number of living plants is estimated at fewer than 300. It is considered Critically Imperiled in global rank which means it is at very high risk of extinction. It has been a federally protected species since 1992. The Wilkesia genus is one of three genera constituting the silversword alliance
Silversword alliance
Silversword alliance refers to an adaptive radiation of over 50 species in the composite or sunflower family, Asteraceae. The group is endemic to Hawaii, and is derived from a single immigrant to the islands...
, a group of highly diverse yet genetically exceedingly closely related species, all thought to be descended from a colonizing ancestor related to the tarweed of North America.
Description
W. hobdyi is a perennialPerennial plant
A perennial plant or simply perennial is a plant that lives for more than two years. The term is often used to differentiate a plant from shorter lived annuals and biennials. The term is sometimes misused by commercial gardeners or horticulturalists to describe only herbaceous perennials...
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...
with branches reaching a length of 60 cm (23.6 in) extending vertically from the base. Branch tips yield whorl, rather than spirals, of narrow, flat, grass-like, somewhat thick 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....
around 7.5–15 cm (3–5.9 in) long. Cream-colored 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 produced in inflorescence
Inflorescence
An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Strictly, it is the part of the shoot of seed plants where flowers are formed and which is accordingly modified...
s 2 cm (0.78740157480315 in) in diameter. Flowering has been observed most often in the winter months, but
also during June. This species is probably pollinated through outcrossing and is probably self-incompatible. Insects are the most likely pollinators. Wilkesia die after flowering.
Habitat
W. hobdyi inhabits dry, nearly vertical rock outcropOutcrop
An outcrop is a visible exposure of bedrock or ancient superficial deposits on the surface of the Earth. -Features:Outcrops do not cover the majority of the Earth's land surface because in most places the bedrock or superficial deposits are covered by a mantle of soil and vegetation and cannot be...
pings in the western part of the island at elevations of 275–400 m (902.2–1,312.3 ft). Rainfall in these sites is less than 1,200 ml per year.
Threats
The primary threat to the species is grazing by feral goats. Native species evolved in the absence of grazing animals and thus did not develop any mechanism for protection. When goats were introduced in the 18th century, many native species were devastated. The existing plants are found only on nearly vertical cliffs which even goats cannot climb. The species is also threatened by encroachment by alien plant species, especially grasses which can smother the plants. Alien grasses also pose fire hazards which endanger the plants. The other species making up the Wilkesia genus, W. gymnoxiphium, is not officially endangered, though it is also found only on Kauai and is not common there.Associated plants
Associated plants include āhinahina (Artemisia spp.) iliau (Wilkesia gymnoxiphiumWilkesia gymnoxiphium
Wilkesia gymnoxiphium , is a species of flowering plant in the sunflower family, Asteraceae, that is endemic to the island of Kauai in Hawaii...
), 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), Lobelia niihauensis, makou (Peucedanum
Peucedanum
Peucedanum is a genus of flowering plant in the carrot family, Apiaceae.-Species:It contains the following species:* Peucedanum angustisectum* Peucedanum camerunensis* Peucedanum cervaria* Peucedanum formosanum Hayata -...
sandwicense
Peucedanum sandwicense
Peucedanum sandwicense is a rare species of flowering plant in the carrot family known by the common name makou. It is endemic to Hawaii, where it is known from Maui, Molokai, Kauai, and Oahu. It is threatened by introduced species of plants and animals...
), kokio ula (Hibiscus kokio
Hawaiian hibiscus
Hawaiian hibiscus are the seven known species of hibiscus regarded as native to Hawaii. Although tourists regularly associate the hibiscus flower with their experiences visiting the US state of Hawaii, and the plant family Malvaceae includes a relatively large number of species that are native to...
), 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...
), alaala wai nui (Peperomia
Peperomia
Peperomia is one of the 2 large genera of the Piperaceae family, with more than 1000 recorded species. Most of them are compact, small perennial epiphytes growing on rotten wood. More than 1500 species have been recorded, occurring in all tropical and subtropical regions of the world, though...
spp.), naio (Myoporum sandwicense
Myoporum sandwicense
Myoporum sandwicense is a species of flowering tree in the figwort family, Scrophulariaceae. Common names include Naio, bastard sandalwood or false sandalwood. It is native to Hawaii and Mangaia in the Cook Islands.-Description:...
), ilima (Sida fallax
Sida fallax
Sida fallax, known as ilima in Hawaiian, is a species of herbaceous flowering plant in the Hibiscus family, Malvaceae, that occurs on most of the Pacific Islands. The flowers are small, in diameter, have five petals, and are a golden yellow in color. Plants may be erect or prostrate and are found...
), uhaloa (Waltheria indica
Waltheria indica
Waltheria indica is a species of flowering plant in the mallow family, Malvaceae, that has a pantropical distribution. It is believed to have originated in the neotropics. Common names include Sleepy Morning, Basora Prieta, Hierba de Soldado, Guimauve, Mauve-gris, Moto-branco, Fulutafu, Kafaki, and...
), aalii (Dodonaea viscosa
Dodonaea viscosa
Dodonaea viscosa is a species of flowering plant in the soapberry family, Sapindaceae, that has a cosmopolitan distribution in tropical, subtropical and warm temperate regions of Africa, the Americas, southern Asia and Australasia.-Description:...
), and kāwelu (Eragrostis variabilis).