genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...
of
cacti
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 ...
in the subfamily
Cactoideae
The Cactoideae are the largest subfamily of the cactus family, Cactaceae. Around 80% of cactus species belong to this subfamily. , the internal classification of the family Cactaceae remained uncertain and subject to change. A classification inc ...
. Its status and
circumscription
Circumscription may refer to:
*Circumscribed circle
*Circumscription (logic)
*Circumscription (taxonomy)
* Circumscription theory, a theory about the origins of the political state in the history of human evolution proposed by the American anthrop ...
remain somewhat uncertain, with the genus containing one to three species (not always the same ones). Molecular phylogenetic data suggest that it consists of three species, including two formerly comprising the genus ''Pseudoacanthocereus''. With this
circumscription
Circumscription may refer to:
*Circumscribed circle
*Circumscription (logic)
*Circumscription (taxonomy)
* Circumscription theory, a theory about the origins of the political state in the history of human evolution proposed by the American anthrop ...
, the species have different growth habits, but share similarities in their flowers, which are white and open at night.
Description
As circumscribed by Korotkova et al. in 2017, the three species of ''Strophocactus'' have tubular to funnel-shaped flowers with tubercules arranged in ribs and
areole
In botany, areoles are small light- to dark-colored bumps on cacti out of which grow clusters of spines. Areoles are important diagnostic features of cacti, and identify them as a family distinct from other succulent plants. Gordon Rowley - W ...
s with bristles. The flowers are white and open at night. They are followed by yellow to brown fruits. Two species (''S. brasiliensis'' and ''S. sicariguensis'') are scrambling or decumbent shrubs, with thin stems (up to 4.5 cm across) and tuberous roots. ''S. sicariguensis'' sometimes has flattened stem segments. The third species, ''S. wittii'', is an
epiphyte
An epiphyte is an organism that grows on the surface of a plant and derives its moisture and nutrients from the air, rain, water (in marine environments) or from debris accumulating around it. The plants on which epiphytes grow are called phoroph ...
with flattened stems that cling to the trunks of trees using aerial roots.
Selenicereus
''Selenicereus'', sometimes known as moonlight cactus, is a genus of epiphytic, lithophytic, and terrestrial cacti, found in Mexico, Central America, the Caribbean and northern South America. The term night-blooming cereus is also sometimes use ...
'', ''Selenicereus'' sect. ''Strophocactus'', so that the species became ''Selenicereus wittii''. In 2003, Ralf Bauer proposed restoring the genus ''Strophocactus'', adding two further species (''S. chontalensis'' and ''S. testudo''). He excluded ''Stophocactus'' from the Hylocereeae. Bauer's actions were based on unpublished DNA sequence data. A
molecular phylogenetic
Molecular phylogenetics () is the branch of phylogeny that analyzes genetic, hereditary molecular differences, predominantly in DNA sequences, to gain information on an organism's evolutionary relationships. From these analyses, it is possible to ...
study of the
Hylocereeae
The Hylocereeae are a tribe of cacti. Most are found in the tropical forests of Central and northern South America, and are climbers or epiphytes, unlike most cacti. The tribe includes between six and eight genera in different circumscriptions ...
in 2017 showed that in neither Hunt's nor Bauer's approach were ''Strophocactus'' and ''Selinicereus''
monophyletic
In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic gro ...
:
''Selenicereus wittii'' formed a
clade
A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...
with two species then placed in ''Pseudoacanthocereus'':
Accordingly, the authors followed Bauer in placing ''Selenicereus wittii'' back in ''Strophocactus'', but now together with the two former ''Pseudoacanthocereus'' species. Like Bauer, they excluded the revised genus ''Strophocactus'' from the Hylocereeae, placing it in the tribe
Echinocereeae
The Echinocereeae are a tribe of cactus, cacti in the subfamily Cactoideae. Since 2006, the tribe has included the former tribe Pachycereeae in many treatments of cactus classification. The exact Circumscription (taxonomy), circumscription of the ...
.
Species
According to Korotkova et al. in 2017, the genus has three species:
Species formerly included in ''Strophocactus'' are:
*''Strophocactus chontalensis'' (Alexander) Ralf Bauer = '' Deamia chontalensis'' (Alexander) Doweld
*''Strophocactus testudo'' (Karw. ex Zucc.) Buxb. ex Krainz = ''
Deamia testudo
''Deamia testudo'' is a species of flowering plant in the family Cactaceae, native from southern Mexico through Central America to Nicaragua. It was first described in 1838. It is a climber or clamberer, with long stems and large white flowers.
...