Pilosocereus robinii
Encyclopedia
Pilosocereus robinii is a species of cactus
known by the common name Key tree-cactus. It is native to the Florida Keys
in the United States. It may occur in Cuba
, but any populations there are unconfirmed. It has been reported from Puerto Rico
, the Virgin Islands
, and Mexico
. It is a rare species which is threatened by the loss of its habitat. It is a federally listed endangered species
of the United States.
This is a large cactus growing erect, often with many parallel or spreading branches. It may become a tree
up to 10 m (32.8 ft) tall. The stem is green in color with a blue tinge when young and has 9 to 13 ribs. The areole
s are covered in long or short hairs and have up to 31 spines each. The spines are no more than a centimeter long. The bell-shaped flower is 5–6 cm (2–2.4 in) long. The outer tepal
s are greenish with brownish midstripes and the inner tepals are white. The flower has a scent similar to garlic
. It opens at night and contains a sweet nectar. The taxonomy
of the species and other Pilosocereus
is not certain. This species is often included in the description of Pilosocereus polygonus.
This cactus grows in upland tropical hardwood hammock
s on limestone
or coral
substrates. It sometimes grows on sparsely vegetated coral rock and just above the high tide mark
. Storm surge
s and sea level rise may inundate its shoreline habitat and increase the salinity
beyond the tolerable range for the cactus.
Other threats to the species include the destruction of its habitat during development. Populations on the Upper
and Lower Matecumbe Key
s have been mostly eliminated due to residential development. Development also leads to habitat fragmentation
. Hurricanes are a threat to the cactus because the winds can break cactus branches or bring down taller vegetation, causing injury; however, hurricane action may open the canopy, providing sunlight to the cactus, which may be beneficial. As of 2009 there are seven known populations of this plant in Florida, located on four of the Florida Keys.
Cactus
A cactus is a member of the plant family Cactaceae. Their distinctive appearance is a result of adaptations to conserve water in dry and/or hot environments. In most species, the stem has evolved to become photosynthetic and succulent, while the leaves have evolved into spines...
known by the common name Key tree-cactus. It is native to the Florida Keys
Florida Keys
The Florida Keys are a coral archipelago in southeast United States. They begin at the southeastern tip of the Florida peninsula, about south of Miami, and extend in a gentle arc south-southwest and then westward to Key West, the westernmost of the inhabited islands, and on to the uninhabited Dry...
in the United States. It may occur in Cuba
Cuba
The Republic of Cuba is an island nation in the Caribbean. The nation of Cuba consists of the main island of Cuba, the Isla de la Juventud, and several archipelagos. Havana is the largest city in Cuba and the country's capital. Santiago de Cuba is the second largest city...
, but any populations there are unconfirmed. It has been reported from Puerto Rico
Puerto Rico
Puerto Rico , officially the Commonwealth of Puerto Rico , is an unincorporated territory of the United States, located in the northeastern Caribbean, east of the Dominican Republic and west of both the United States Virgin Islands and the British Virgin Islands.Puerto Rico comprises an...
, the Virgin Islands
Virgin Islands
The Virgin Islands are the western island group of the Leeward Islands, which are the northern part of the Lesser Antilles, which form the border between the Caribbean Sea and the Atlantic Ocean...
, and Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
. It is a rare species which is threatened by the loss of its habitat. It is a federally listed endangered species
Endangered 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.
This is a large cactus growing erect, often with many parallel or spreading branches. It may become a 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 10 m (32.8 ft) tall. The stem is green in color with a blue tinge when young and has 9 to 13 ribs. The areole
Areole
Areoles are an important diagnostic feature of cacti, and identify them as a family distinct from other succulent plants. The areoles on cacti are clearly visible; they generally appear as small light- to dark-colored bumps, out of which grow clusters of spines...
s are covered in long or short hairs and have up to 31 spines each. The spines are no more than a centimeter long. The bell-shaped flower is 5–6 cm (2–2.4 in) long. The outer tepal
Tepal
Tepals are elements of the perianth, or outer part of a flower, which include the petals or sepals. The term tepal is more often applied specifically when all segments of the perianth are of similar shape and color, or undifferentiated, which is called perigone...
s are greenish with brownish midstripes and the inner tepals are white. The flower has a scent similar to garlic
Garlic
Allium sativum, commonly known as garlic, is a species in the onion genus, Allium. Its close relatives include the onion, shallot, leek, chive, and rakkyo. Dating back over 6,000 years, garlic is native to central Asia, and has long been a staple in the Mediterranean region, as well as a frequent...
. It opens at night and contains a sweet nectar. The taxonomy
Taxonomy
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...
of the species and other Pilosocereus
Pilosocereus
Pilosocereus is a genus of cactus.The commonly cultivated Pilosocereus pachycladus is a blue cactus with hairy areoles that emit golden spines.-Synonymy:...
is not certain. This species is often included in the description of Pilosocereus polygonus.
This cactus grows in upland tropical hardwood hammock
Tropical hardwood hammock
Tropical hardwood hammocks are closed canopy forests, dominated by a diverse assemblage of evergreen and semi-deciduous tree and shrub species, mostly of West Indian origin...
s on limestone
Limestone
Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....
or coral
Coral
Corals are marine animals in class Anthozoa of phylum Cnidaria typically living in compact colonies of many identical individual "polyps". The group includes the important reef builders that inhabit tropical oceans and secrete calcium carbonate to form a hard skeleton.A coral "head" is a colony of...
substrates. It sometimes grows on sparsely vegetated coral rock and just above the high tide mark
Strandline
The strandline, or high water mark, is the area at the top of a beach where debris is deposited. Where there are tides, this line is formed by the highest position of the tide, and moves up and down the beach on a fortnightly cycle...
. Storm surge
Storm surge
A storm surge is an offshore rise of water associated with a low pressure weather system, typically tropical cyclones and strong extratropical cyclones. Storm surges are caused primarily by high winds pushing on the ocean's surface. The wind causes the water to pile up higher than the ordinary sea...
s and sea level rise may inundate its shoreline habitat and increase the salinity
Salinity
Salinity is the saltiness or dissolved salt content of a body of water. It is a general term used to describe the levels of different salts such as sodium chloride, magnesium and calcium sulfates, and bicarbonates...
beyond the tolerable range for the cactus.
Other threats to the species include the destruction of its habitat during development. Populations on the Upper
Upper Matecumbe Key
Upper Matecumbe Key is an island in the upper Florida Keys.U.S. 1 crosses the key at approximately mile markers 79—83.5, between Windley Key and Lower Matecumbe Key....
and Lower Matecumbe Key
Lower Matecumbe Key
Lower Matecumbe Key is an island in the upper Florida Keys.It is located on U.S. 1 between mile markers 75--78.All of the key is within the Village of Islamorada as of November 4, 1997, when it was incorporated....
s have been mostly eliminated due to residential development. Development also leads to habitat fragmentation
Habitat fragmentation
Habitat fragmentation as the name implies, describes the emergence of discontinuities in an organism's preferred environment , causing population fragmentation...
. Hurricanes are a threat to the cactus because the winds can break cactus branches or bring down taller vegetation, causing injury; however, hurricane action may open the canopy, providing sunlight to the cactus, which may be beneficial. As of 2009 there are seven known populations of this plant in Florida, located on four of the Florida Keys.