''Haptanthus'' is a
monotypic genus
In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispec ...
containing the sole species ''Haptanthus hazlettii'', a shrub or small tree known only from the locality of
Matarras in the
Arizona Municipality in
Honduras. Its flowers are unique among the
flowering plant
Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek words ('container, vessel') and ('seed'), and refers to those plants th ...
s. A single "female" (carpellate) flower has two branches on either side which carry "male" (staminate) flowers. The flowers are very simple, lacking obvious
sepal
A sepal () is a part of the flower of angiosperms (flowering plants). Usually green, sepals typically function as protection for the flower in bud, and often as support for the petals when in bloom., p. 106 The term ''sepalum'' was coine ...
s or
petals. The
family
Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...
placement of the genus has been uncertain, but based on
molecular phylogenetic research, it is included in the family
Buxaceae
The Buxaceae are a small family of six genera and about 123 known species of flowering plants. They are shrubs and small trees, with a cosmopolitan distribution. A seventh genus, sometimes accepted in the past (''Notobuxus''), has been shown ...
.
[ Very few individuals have ever been found and its habitat is threatened by logging.
]
Description
''Haptanthus hazlettii'' is a shrub[ or tree.][ It has opposite leaves spaced at 5.5–6.0 cm apart, usually arranged in two ranks (distichous). The leaves are simple with untoothed (entire) margins. There are no ]stipule
In botany, a stipule is an outgrowth typically borne on both sides (sometimes on just one side) of the base of a leafstalk (the petiole). Stipules are considered part of the anatomy of the leaf of a typical flowering plant, although in many speci ...
s. The leaf stalk ( petiole) is short, 7–8 mm long, the leaf blade (lamina) 10–13.5 cm long by 4.1–5.6 cm wide. The entire plant is hairless (glabrous).[
The flowers are unisexual, carried on the same ]inflorescence
An inflorescence is a group or cluster of flowers arranged on a Plant stem, stem that is composed of a main branch or a complicated arrangement of branches. Morphology (biology), Morphologically, it is the modified part of the shoot of sperma ...
(i.e. the plant is monoecious). One (or occasionally two) inflorescences emerge from a leaf axil, with at least five inflorescence-bearing axils per fertile branch. The inflorescences have a unique structure among flowering plants. In the centre there is a single carpellate ("female") flower. This lacks obvious petals or sepal
A sepal () is a part of the flower of angiosperms (flowering plants). Usually green, sepals typically function as protection for the flower in bud, and often as support for the petals when in bloom., p. 106 The term ''sepalum'' was coine ...
s (although there are small bracts below the flower which some researchers have suggested may be the remnants of the perianth[), and consists solely of a single-celled ( unilocular) ovary, 5 mm long by 2 mm wide, surmounted by three curved 4 mm long stigmas. On either side of the solitary carpellate flower there are two branches each with five or six staminate ("male") flowers arranged at 1–3 mm intervals.][
The structure of the staminate flowers has been interpreted differently. The original describers of the species, ]Aaron Goldberg
Aaron Goldberg (born April 30, 1974), is an American jazz pianist. Described by ''The New York Times'' as a "post-bop pianist of exemplary taste and range," Goldberg has released five albums as a solo artist and has performed and collaborated wi ...
and Cirilo Nelson, considered that each staminate flower was basically just a single stamen, with a flattened filament about 3–5 mm long grading into an anther about 2.5 mm long.[ Two staminate flowers from the original specimen were re-examined by Andrew Doust and Peter Stevens. They concluded that each staminate flower definitely had two anthers, closely pressed together. They were unable to make a firm choice between two interpretations. The first is that the staminate flowers are basically as described by Goldberg and Nelson, except there are two stamens with fused or closely pressed filaments and anthers rather than one. The second, which they preferred, is that Goldberg and Nelson's "filament" is actually a pedicel (i.e. a stem on which the parts of the flower are carried) and that their "anther" consists of two closely pressed structures each made up of a ]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 ...
with a fused anther inside it. Either way, the flowers of ''Haptanthus hazlettii'' have "a morphology unlike that of any other angiosperm".[
]
Taxonomy
The sole species was first discovered in 1980 when a single specimen was collected by Donald L. Hazlett.[ It was described scientifically in 1989 by Goldberg and Nelson, as a new genus and species, ''Haptanthus hazlettii''. Initially Goldberg and Nelson were unable to assign ''Haptanthus'' to a ]family
Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...
.[ Nelson later placed it in its own family, Haptanthaceae.][ In 2005, an attempt was made to obtain DNA for sequencing from the only known specimen, but this failed. Based on an analysis of the morphology of the specimen, Doust and Stevens suggested that ''Haptanthus'' was possibly related to the Buxales.][ The APG III system of 2009 accepted the family Haptanthaceae, placing it in the order Buxales, along with the Buxaceae.][ The close relationship with the Buxaceae was confirmed in 2011 when DNA was successfully obtained from a newly collected specimen. Molecular phylogenetic analysis showed that ''Haptanthus'' belongs inside the family Buxaceae rather than in a family of its own.][ The ]APG IV system
The APG IV system of flowering plant classification is the fourth version of a modern, mostly molecular-based, system of plant taxonomy for flowering plants (angiosperms) being developed by the Angiosperm Phylogeny Group (APG). It was published ...
of 2016 includes ''Haptanthus'' in the family Buxaceae.
Distribution, habitat and conservation
''Haptanthus hazlettii'' has only been found in a very small area of tropical rain forest on the northern coast of Honduras, close to Matarras in the Arizona Municipality.[ After the original specimen was collected in 1989, numerous attempts were made to find the species again but without success; the area had become covered with grass following tree clearance. It was thought that the species was perhaps extinct.][ In 2010 an expedition organized by Alexey Shipunov and Ekaterina Shipunova found a single tree 2 km from the original collection point. A few more were later found nearby. Work to conserve the species is being led by the Lancetilla Botanical Garden of ]Tela
Tela is a town, with a population of 38,030 (2020 calculation), and a municipality in Honduras on the northern Caribbean coast. It is located in the department of Atlantida.
History
Colonial era
Tela was founded by the Spanish conquistador ...
, Honduras.[
]
References
External links
* – includes photographs of the original 1980 specimen
{{Taxonbar, from1=Q15715555, from2=Q133951
Buxaceae
Eudicot genera
Monotypic eudicot genera
Flora of Honduras
Critically endangered plants