Dudleya traskiae
Encyclopedia
Dudleya traskiae is a rare succulent plant
known by the common name Santa Barbara Island liveforever. This dudleya
is endemic to Santa Barbara Island
, one of the Channel Islands of California
, where it grows on rocky bluffs. The plant has a basal rosette of flat, spade-shaped fleshy leaves up to 15 centimeters long, which are pale green to yellowish. It erects tall stems bearing dense, rounded inflorescence
s of many bright yellow flowers.
, with a branched primary stem (caudex
) and are composed of one to several hundred rosettes. The branching of the stem is dichotomous. The rosette leaves number 25-35, are strap-shaped - oblanceolate to subacuminate and are 4-15 cm long and 1-4 cm wide. Leaves
may be green or glaucous with a waxy covering. The flowering stems are axillary and flowering is indeterminate in paniculate or cymose clusters. The petal
s (5) are bright yellow, often with red veins, fused below and curving outward in the upper half. Stamen
s (10) are borne on the corolla tube. The fruit
is composed of 5 carpels that are spreading in age, 7-8 mm long. Seeds are many and minute, narrow and pointed. Dudleya traskiae is tetraploid with a chromosome number of 34. Flowering most commonly occurs from May-July, although flowering may begin as early as mid-February.
n, though it also extends north into southern Oregon
, east to central Arizona
and southern Nevada
, and south to the tip of Baja California
, Mexico. Dudleya taxa occur on each of the eight Channel Islands. Dudleya traskiae is known only from Santa Barbara Island, California.
There are ten occurrences on this 652-acre island.
All of the known sites supporting Dudleya traskiae are in rocky areas on the steep slopes of the island's perimeter or on outcrops within shallow canyons where vegetation is low-growing. With the exception of a small population on the far western portion of the island, all locations, historic as well as present day (as of 1989) occur on the eastern, southeastern and southwestern slopes of the island. No Dudleya traskiae plants presently occur on the northern and north-western sides of the island although they do occur elsewhere on north-facing slopes. The habitat of Dudleya traskiae has been described as a maritime cactus scrub, and by Holland (1986) as southern coastal bluff scrub. This assemblage of plants, characterized by cholla
(Cylindropuntia prolifera
), prickly pear
(O. oricola
and O. littoralis
), boxthorn (Lycium californicum
), Santa Barbara Island buckwheat (Eriogonum giganteum
ssp. compactum) and annual forb
s and grass
es, is restricted to the perimeter of the island and south-facing slopes of the canyons.
of the United States.
It and other native flora were heavily impacted in the 19th century by the presence of hordes of feral goat
s. The goats were followed by other introduced species
, including cat
s, sheep, New Zealand red rabbit
s, and Belgian hares
. In the first half of the 20th century the island supported agriculture
, producing barley
, oat
s, and potato
es.
By 1984 the total number of D. traskiae on the island was about 534. By 2004 the total number was estimated to be around 852. About 80 plants were cultivated and planted in appropriate habitat.
D. traskiae is slow to increase its population due to several factors. Some plants produce few seeds, and some produce few seeds that are viable. Seeds produced are sometimes taken and consumed by deer mice
(Peromyscus maniculatus ssp. exilis). On the other hand, when the mice cache the seeds, they may aid in its difficult seed dispersal
. Seedling
s that successfully emerge are consumed by the mice and by the larva
e of owlet moths. Others perished in drought
.
Other threats include damage from the activity of nesting Brown Pelican
s, erosion
, and introduced plant species
.
Conservation efforts include keeping people away from sensitive habitat, performing research, and planting more individuals in the habitat. All the introduced herbivores, including the particularly destructive rabbits and hares, have been removed from the island.
Succulent plant
Succulent plants, also known as succulents or fat plants, are water-retaining plants adapted to arid climates or soil conditions. Succulent plants store water in their leaves, stems, and also in roots...
known by the common name Santa Barbara Island liveforever. This dudleya
Dudleya
Dudleya is a genus of succulent perennials, consisting of about 45 species in southwest North America.Many plants in the Dudleya genus were formerly classified as Echeveria....
is endemic to Santa Barbara Island
Santa Barbara Island
Santa Barbara Island is a small island of the Channel Islands archipelago in California. It is located about off the Southern California coast from the Palos Verdes Peninsula, near Los Angeles in Ventura County, California....
, one of the Channel Islands of California
Channel Islands of California
The Channel Islands of California are a chain of eight islands located in the Pacific Ocean off the coast of Southern California along the Santa Barbara Channel in the United States of America...
, where it grows on rocky bluffs. The plant has a basal rosette of flat, spade-shaped fleshy leaves up to 15 centimeters long, which are pale green to yellowish. It erects tall stems bearing dense, rounded 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 of many bright yellow flowers.
Description
Dudleya traskiae is a perennial succulent herb with foliage leaves in a basal rosette. The plants are evergreenEvergreen
In botany, an evergreen plant is a plant that has leaves in all seasons. This contrasts with deciduous plants, which completely lose their foliage during the winter or dry season.There are many different kinds of evergreen plants, both trees and shrubs...
, with a branched primary stem (caudex
Caudex
A caudex is a form of stem morphology appearing as a thickened, short, perennial stem that is either underground or near ground level . It may be swollen for the purpose of water storage, especially in xerophytes...
) and are composed of one to several hundred rosettes. The branching of the stem is dichotomous. The rosette leaves number 25-35, are strap-shaped - oblanceolate to subacuminate and are 4-15 cm long and 1-4 cm wide. 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....
may be green or glaucous with a waxy covering. The flowering stems are axillary and flowering is indeterminate in paniculate or cymose clusters. The 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 (5) are bright yellow, often with red veins, fused below and curving outward in the upper half. Stamen
Stamen
The stamen is the pollen producing reproductive organ of a flower...
s (10) are borne on the corolla tube. 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 composed of 5 carpels that are spreading in age, 7-8 mm long. Seeds are many and minute, narrow and pointed. Dudleya traskiae is tetraploid with a chromosome number of 34. Flowering most commonly occurs from May-July, although flowering may begin as early as mid-February.
Distribution and habitat
The genus Dudleya is primarily CaliforniaCalifornia
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
n, though it also extends north into southern Oregon
Oregon
Oregon is a state in the Pacific Northwest region of the United States. It is located on the Pacific coast, with Washington to the north, California to the south, Nevada on the southeast and Idaho to the east. The Columbia and Snake rivers delineate much of Oregon's northern and eastern...
, east to central Arizona
Arizona
Arizona ; is a state located in the southwestern region of the United States. It is also part of the western United States and the mountain west. The capital and largest city is Phoenix...
and southern Nevada
Nevada
Nevada is a state in the western, mountain west, and southwestern regions of the United States. With an area of and a population of about 2.7 million, it is the 7th-largest and 35th-most populous state. Over two-thirds of Nevada's people live in the Las Vegas metropolitan area, which contains its...
, and south to the tip of Baja California
Baja California
Baja California officially Estado Libre y Soberano de Baja California is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is both the northernmost and westernmost state of Mexico. Before becoming a state in 1953, the area was known as the North...
, Mexico. Dudleya taxa occur on each of the eight Channel Islands. Dudleya traskiae is known only from Santa Barbara Island, California.
There are ten occurrences on this 652-acre island.
All of the known sites supporting Dudleya traskiae are in rocky areas on the steep slopes of the island's perimeter or on outcrops within shallow canyons where vegetation is low-growing. With the exception of a small population on the far western portion of the island, all locations, historic as well as present day (as of 1989) occur on the eastern, southeastern and southwestern slopes of the island. No Dudleya traskiae plants presently occur on the northern and north-western sides of the island although they do occur elsewhere on north-facing slopes. The habitat of Dudleya traskiae has been described as a maritime cactus scrub, and by Holland (1986) as southern coastal bluff scrub. This assemblage of plants, characterized by cholla
Cylindropuntia
Cylindropuntia is a genus of cacti , containing the chollas. They were formerly treated as a subgenus of Opuntia but have now been separated based on their cylindrical stems and the presence of papery epidermal sheaths on the spines...
(Cylindropuntia prolifera
Cylindropuntia prolifera
Cylindropuntia prolifera, known by the common name Coastal cholla, is a species of cactus.-Description:Cylindropuntia prolifera is a mostly erect, treelike cactus which can approach 3 meters in maximum height. The gray-green segments are narrow and cylindrical, surfaced in fleshy tubercles bearing...
), prickly pear
Opuntia
Opuntia, also known as nopales or paddle cactus , is a genus in the cactus family, Cactaceae.Currently, only prickly pears are included in this genus of about 200 species distributed throughout most of the Americas. Chollas are now separated into the genus Cylindropuntia, which some still consider...
(O. oricola
Opuntia oricola
Opuntia oricola is a species of prickly pear cactus known by the common name chaparral prickly pear. It is native to southern California and Baja California, where it grows in coastal sage scrub and chaparral habitats.-Description:...
and O. littoralis
Opuntia littoralis
Opuntia littoralis is a species of prickly pear cactus known by the common name coastal prickly pear.-Distribution:Opuntia littoralis is native to southern California and Baja California, where it grows in coastal sage scrub and chaparral habitats...
), boxthorn (Lycium californicum
Lycium californicum
Lycium californicum is a spreading shrub in the nightshade family known by the common names California boxthorn and California desert-thorn....
), Santa Barbara Island buckwheat (Eriogonum giganteum
Eriogonum giganteum
Eriogonum giganteum is a species of wild buckwheat.-Description:Eriogonum giganteum is variable in size, from a thin half a meter in height and width to a sprawling or rounded bush over three meters high and wide. The leathery, woolly, oval-shaped leaves are clustered sparsely along the mostly...
ssp. compactum) and annual forb
Forb
A forb is a herbaceous flowering plant that is not a graminoid . The term is used in biology and in vegetation ecology, especially in relation to grasslands and understory.-Etymology:...
s and grass
Grass
Grasses, or more technically graminoids, are monocotyledonous, usually herbaceous plants with narrow leaves growing from the base. They include the "true grasses", of the Poaceae family, as well as the sedges and the rushes . The true grasses include cereals, bamboo and the grasses of lawns ...
es, is restricted to the perimeter of the island and south-facing slopes of the canyons.
Conservation
This plant is federally listed as an endangered speciesEndangered species
An endangered species is a population of organisms which is at risk of becoming extinct because it is either few in numbers, or threatened by changing environmental or predation parameters...
of the United States.
It and other native flora were heavily impacted in the 19th century by the presence of hordes of feral goat
Feral goat
The feral goat is the domestic goat when it has become established in the wild. Feral goats occur in Australia, New Zealand, Ireland, Great Britain, Hawaii, the Galapagos and in many other parts of the world...
s. The goats were followed by other introduced species
Introduced species
An introduced species — or neozoon, alien, exotic, non-indigenous, or non-native species, or simply an introduction, is a species living outside its indigenous or native distributional range, and has arrived in an ecosystem or plant community by human activity, either deliberate or accidental...
, including 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, sheep, New Zealand red rabbit
New Zealand red rabbit
New Zealand red rabbits is a rabbit breed, which despite the name, is American in origin. New Zealand rabbits are available in three ARBA-recognized colors: white, red, and black...
s, and Belgian hares
Belgian Hare
The Belgian Hare is a fancy breed of domestic rabbit, that was developed through selective breeding to closely resemble the wild hare in physical appearance, and is believed to be one of the most intelligent and active breeds of domestic rabbit...
. In the first half of the 20th century the island supported agriculture
Agriculture
Agriculture is the cultivation of animals, plants, fungi and other life forms for food, fiber, and other products used to sustain life. Agriculture was the key implement in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that nurtured the...
, producing barley
Barley
Barley is a major cereal grain, a member of the grass family. It serves as a major animal fodder, as a base malt for beer and certain distilled beverages, and as a component of various health foods...
, oat
Oat
The common oat is a species of cereal grain grown for its seed, which is known by the same name . While oats are suitable for human consumption as oatmeal and rolled oats, one of the most common uses is as livestock feed...
s, and potato
Potato
The potato is a starchy, tuberous crop from the perennial Solanum tuberosum of the Solanaceae family . The word potato may refer to the plant itself as well as the edible tuber. In the region of the Andes, there are some other closely related cultivated potato species...
es.
By 1984 the total number of D. traskiae on the island was about 534. By 2004 the total number was estimated to be around 852. About 80 plants were cultivated and planted in appropriate habitat.
D. traskiae is slow to increase its population due to several factors. Some plants produce few seeds, and some produce few seeds that are viable. Seeds produced are sometimes taken and consumed by deer mice
Peromyscus maniculatus
Peromyscus maniculatus is a rodent native to North America. It is most commonly called the Deer Mouse, although that name is common to most species of Peromyscus and is fairly widespread across the continent, with the major exception being the southeast United States and the far north.Like other...
(Peromyscus maniculatus ssp. exilis). On the other hand, when the mice cache the seeds, they may aid in its difficult seed dispersal
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...
. Seedling
Seedling
thumb|Monocot and dicot seedlingsA seedling is a young plant sporophyte developing out of a plant embryo from a seed. Seedling development starts with germination of the seed. A typical young seedling consists of three main parts: the radicle , the hypocotyl , and the cotyledons...
s that successfully emerge are consumed by the mice and by the larva
Larva
A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...
e of owlet moths. Others perished in drought
Drought
A drought is an extended period of months or years when a region notes a deficiency in its water supply. Generally, this occurs when a region receives consistently below average precipitation. It can have a substantial impact on the ecosystem and agriculture of the affected region...
.
Other threats include damage from the activity of nesting Brown Pelican
Brown Pelican
The Brown Pelican is the smallest of the eight species of pelican, although it is a large bird in nearly every other regard. It is in length, weighs from and has a wingspan from .-Range and habits:...
s, erosion
Erosion
Erosion is when materials are removed from the surface and changed into something else. It only works by hydraulic actions and transport of solids in the natural environment, and leads to the deposition of these materials elsewhere...
, and introduced plant species
Introduced species
An introduced species — or neozoon, alien, exotic, non-indigenous, or non-native species, or simply an introduction, is a species living outside its indigenous or native distributional range, and has arrived in an ecosystem or plant community by human activity, either deliberate or accidental...
.
Conservation efforts include keeping people away from sensitive habitat, performing research, and planting more individuals in the habitat. All the introduced herbivores, including the particularly destructive rabbits and hares, have been removed from the island.