''Pilosocereus robinii'' is a species of

cactus A cactus (, or less commonly, cactus) is a member of the plant family Cactaceae, a family comprising about 127 genera with some 1750 known species of the order Caryophyllales. The word ''cactus'' derives, through Latin, from the Ancient Greek ...

known by the common name Key tree-cactus. It is native to the

Florida Keys The Florida Keys are a coral cay archipelago located off the southern coast of Florida, forming the southernmost part of the continental United States. They begin at the southeastern coast of the Florida peninsula, about south of Miami, and e ...

in the United States.USFWS
''Pilosocereus robinii'' Five-year Review.
August 2010. It also occurs in Western

Cuba Cuba ( , ), officially the Republic of Cuba ( es, República de Cuba, links=no ), is an island country comprising the island of Cuba, as well as Isla de la Juventud and several minor archipelagos. Cuba is located where the northern Caribbea ...

and the Northern

Bahamas The Bahamas (), officially the Commonwealth of The Bahamas, is an island country within the Lucayan Archipelago of the West Indies in the Atlantic Ocean, North Atlantic. It takes up 97% of the Lucayan Archipelago's land area and is home to ...

. It has been erroneously reported from

Puerto Rico Puerto Rico (; abbreviated PR; tnq, Boriken, ''Borinquen''), officially the Commonwealth of Puerto Rico ( es, link=yes, Estado Libre Asociado de Puerto Rico, lit=Free Associated State of Puerto Rico), is a Caribbean island and Unincorporated ...

,''Pilosocereus robinii''.
The Nature Conservancy. the

Virgin Islands The Virgin Islands ( es, Islas Vírgenes) are an archipelago in the Caribbean Sea. They are geologically and biogeographically the easternmost part of the Greater Antilles, the northern islands belonging to the Puerto Rico Trench and St. Croix ...

, and

Mexico Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...

. It is a rare species which is threatened by the loss of its habitat. It is a federally listed

endangered species An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching and inv ...

of the United States.

Description

This is a large cactus growing erect, often with many parallel or spreading branches. It may become a

tree In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, including only woody plants with secondary growth, plants that are ...

up to tall. The stem is green in color with a blue tinge when young and has 9 to 13 ribs. The areoles 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 long. The outer

tepal A tepal is one of the outer parts of a flower (collectively the perianth). The term is used when these parts cannot easily be classified as either sepals or petals. This may be because the parts of the perianth are undifferentiated (i.e. of very ...

s are greenish with brownish midstripes and the inner tepals are white. The flower has a scent similar to

garlic Garlic (''Allium sativum'') is a species of bulbous flowering plant in the genus ''Allium''. Its close relatives include the onion, shallot, leek, chive, Allium fistulosum, Welsh onion and Allium chinense, Chinese onion. It is native to South A ...

.''Pilosocereus robinii''.
Center for Plant Conservation. It opens at night and contains a sweet

nectar Nectar is a sugar-rich liquid produced by plants in glands called nectaries or nectarines, either within the flowers with which it attracts pollinating animals, or by extrafloral nectaries, which provide a nutrient source to animal mutualists ...

Taxonomy

The

taxonomy Taxonomy is the practice and science of categorization or classification. A taxonomy (or taxonomical classification) is a scheme of classification, especially a hierarchical classification, in which things are organized into groups or types. ...

of the species and other ''

Pilosocereus ''Pilosocereus'' (from Latin, "hairy cereus") is a genus of cactus native to the Neotropics. Tree cactus is a common name for ''Pilosocereus'' species. The commonly cultivated ''Pilosocereus pachycladus'' ( syn. ''Pilosocereus azureus'') is a bl ...

'' has only been cleared recently. This species was formerly included in the description of '' Pilosocereus polygonus''.

Habitat

This cactus grows in upland tropical hardwood hammocks on

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...

coral Corals are marine invertebrates within the class Anthozoa of the phylum Cnidaria. They typically form compact colonies of many identical individual polyps. Coral species include the important reef builders that inhabit tropical oceans and sec ...

substrates. It sometimes grows on sparsely vegetated coral rock and just above the high tide mark. There are only 4 of these plants that produce fruits. Their seeds are dispersed by frugivores. Windy conditions would also spread this cactus' seeds; the wind would break off branches and allow propagation to occur. The branches would root themselves in the soil and stems would grow out from them.

Storm surge A storm surge, storm flood, tidal surge, or storm tide is a coastal flood or tsunami-like phenomenon of rising water commonly associated with low-pressure weather systems, such as cyclones. It is measured as the rise in water level above the n ...

s and

sea level rise Globally, sea levels are rising due to human-caused climate change. Between 1901 and 2018, the globally averaged sea level rose by , or 1–2 mm per year on average.IPCC, 2019Summary for Policymakers InIPCC Special Report on the Ocean and Cry ...

may inundate its shoreline habitat and increase the

salinity Salinity () is the saltiness or amount of salt dissolved in a body of water, called saline water (see also soil salinity). It is usually measured in g/L or g/kg (grams of salt per liter/kilogram of water; the latter is dimensionless and equal ...

beyond the tolerable range for the cactus.

Conservation

Other threats to the species include the destruction of its habitat during development. Populations on the Upper and Lower Matecumbe Keys have been mostly eliminated due to residential development. Development also leads to

habitat fragmentation Habitat fragmentation describes the emergence of discontinuities (fragmentation) in an organism's preferred environment (habitat), causing population fragmentation and ecosystem decay. Causes of habitat fragmentation include geological processes ...

Hurricane A tropical cyclone is a rapidly rotating storm system characterized by a low-pressure center, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain and squalls. Depend ...

s 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.

References

*Goodman, Joie, et al. “Differential Response to Soil Salinity in Endangered Key Tree Cactus: Implications for Survival in a Changing Climate.” PLoS ONE, vol. 7, no. 3, 2012, https://doi.org/10.1371/journal.pone.0032528.

External links

USDA Plants Profile for ''Pilosocereus robinii''
{{Taxonbar, from=Q7194318 robinii Cacti of North America Cacti of Mexico Cacti of the United States Flora of the Caribbean Flora of Florida Flora of Puerto Rico Critically endangered flora of the United States Critically endangered biota of Mexico Critically endangered flora of North America Plants described in 1957