Poranthereae
Encyclopedia
Poranthereae is a tribe
in the flowering plant
family
Phyllanthaceae
. It is one of ten tribes in the family, and one of four tribes in the subfamily
Phyllanthoideae. Poranthereae comprises about 111 species
, distributed into eight genera
. The largest genera and the number of species in each are Actephila (31), Meineckia (30), and Andrachne (22).
The tribe consists of herbs
, shrub
s, and small to medium tree
s. They have a cosmopolitan distribution
, occurring on all continent
s, except Antarctica. The circumscription
and classification
of Poranthereae were substantially revised following phylogenetic analysis of DNA sequence
s from members of the family Phyllanthaceae.
Within Poranthereae, groups of related
genera are strongly correlated with habitat
and geographical
distribution
. For example, Notoleptopus, Pseudophyllanthus, and Poranthera are restricted to the Old World
Southern Hemisphere
.
herbs
, shrub
s, or tree
s to 6m tall. Thorns or other armature
absent. Stipule
s present, sometimes leaf-like is some Meineckia. Petioles
present or absent, not pulvinate
. leaves
simple, arrangement
alternate, subopposite, or in some Poranthera, opposite. margins entire. Inflorescence
s axillary, or rarely, apparently terminal. Flower
s solitary to fasciculate. Sepal
s free, greenish, persistent. Petal
s present or absent, often partly adnate
to the nectary disk, equal to the sepals or shorter, white or greenish, usually larger in staminate
than in pistillate
flowers. Disk present, extrastaminal; annular
or divided into alternisepalous segments or glands. Stamens opposite the sepals, free or fused
for up to 9/10 of their length. Anthers latrorse, at least in bud
, opening
by longitudinal slits, or in Poranthera, by pores. Ovary
usually divided into three locule
s. Two ovule
s in each locule. Styles free to almost completely fused. Fruit
explosively dehiscent
. Seed
s usually two per locule; sometimes one in Actephila and Meineckia.
of Poranthereae. In most species, the petals of staminate flowers are almost as large as the sepals, and the petals of pistillate flowers are much smaller.
Petal loss or reduction has occurred at least four times in the evolution
of Poranthereae. It has been observed
in Poranthera, Actephila, Andrachne, and Meineckia. In one species of Poranthera and in several of Actephila, the petal size is variable, and sometimes the petals are completely absent. In some species of Actephila, petal number as well as size is variable. In Andrachne subgenus
Phyllanthidea, staminate petals are lost in some species, and pistillate petals are lost in others. Petals are entirely absent in Meineckia subgenus Meineckia.
for the tribe is Poranthera, which was so named because the anthers open poricidally rather than by longitudinal slits.
Two similar treatments of Poranthereae were presented by Grady Webster
and Alan Radcliffe-Smith, in 1994 and 2001, respectively. These authors considered Poranthereae to be part of Euphorbiaceae
sensu lato, a taxon
that is now known to be paraphyletic. Their circumscription of the tribe was different from that which is now generally accepted.
Poranthaceae, as currently understood, was first recognized in phylogenetic analyses of DNA sequences of selected gene
s. The existence of this clade
was not entirely unanticipated and had been at least partially suggested in several studies
based on morphology
. The tribe was formally established in its present form in a revision of Phyllanthaceae in 2006. In 2007, a phylogeny of Poranthereae was presented by Vorontsova et alii, based on DNA sequences of matK and ITS
. This paper included much on the taxonomic history
of the tribe.
In 2008, based on molecular phylogenetic studies, Vorontsova and Hoffmann published a revised classification of the tribe. A description of each genus and a key
to the genera were included. Four of the genera recognized by Radcliffe-Smith (Zimmermannia, Zimmermanniopsis, Archileptopus, and Oreoporanthera) were sunk into other genera and three new genera were established. Notoleptopus was "carved" out of Leptopus, while Pseudophyllanthus and Phyllanthopsis were removed from Andrachne.
Some of the genera in Poranthereae are still in need of revision. This is especially true of Actephila, the most variable and least understood genus in the tribe.
is based on the one by Vorontsova and Hoffmann (2008). All branches have at least 75% bootstrap
support. Branches with less statistical support
are collapsed to form the tetratomy
in the tree below.
Tribe (biology)
In biology, a tribe is a taxonomic rank between family and genus. It is sometimes subdivided into subtribes.Some examples include the tribes: Canini, Acalypheae, Hominini, Bombini, and Antidesmeae.-See also:* Biological classification* Rank...
in the flowering plant
Flowering plant
The flowering plants , also known as Angiospermae or Magnoliophyta, are the most diverse group of land plants. Angiosperms are seed-producing plants like the gymnosperms and can be distinguished from the gymnosperms by a series of synapomorphies...
family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Phyllanthaceae
Phyllanthaceae
Phyllanthaceae is a family of flowering plants in the eudicot order Malpighiales. It is most closely related to the family Picrodendraceae. The Phyllanthaceae are most numerous in the tropics, with many in the south temperate zone, and a few ranging as far north as the middle of the north temperate...
. It is one of ten tribes in the family, and one of four tribes in the subfamily
Taxonomic rank
In biological classification, rank is the level in a taxonomic hierarchy. Examples of taxonomic ranks are species, genus, family, and class. Each rank subsumes under it a number of less general categories...
Phyllanthoideae. Poranthereae comprises about 111 species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
, distributed into eight genera
Genera
Genera is a commercial operating system and development environment for Lisp machines developed by Symbolics. It is essentially a fork of an earlier operating system originating on the MIT AI Lab's Lisp machines which Symbolics had used in common with LMI and Texas Instruments...
. The largest genera and the number of species in each are Actephila (31), Meineckia (30), and Andrachne (22).
The tribe consists of herbs
Herbaceous plant
A herbaceous plant is a plant that has leaves and stems that die down at the end of the growing season to the soil level. They have no persistent woody stem above ground...
, shrub
Shrub
A shrub or bush is distinguished from a tree by its multiple stems and shorter height, usually under 5–6 m tall. A large number of plants may become either shrubs or trees, depending on the growing conditions they experience...
s, and small to medium 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...
s. They have a cosmopolitan distribution
Cosmopolitan distribution
In biogeography, a taxon is said to have a cosmopolitan distribution if its range extends across all or most of the world in appropriate habitats. For instance, the killer whale has a cosmopolitan distribution, extending over most of the world's oceans. Other examples include humans, the lichen...
, occurring on all continent
Continent
A continent is one of several very large landmasses on Earth. They are generally identified by convention rather than any strict criteria, with seven regions commonly regarded as continents—they are : Asia, Africa, North America, South America, Antarctica, Europe, and Australia.Plate tectonics is...
s, except Antarctica. The circumscription
Circumscription (taxonomy)
In taxonomy, circumscription is the definition of the limits of a taxonomic group of organisms. One goal of taxonomy is to achieve a stable circumscription for every taxonomic group. Achieving stability can be simple or difficult....
and classification
Biological classification
Biological classification, or scientific classification in biology, is a method to group and categorize organisms by biological type, such as genus or species. Biological classification is part of scientific taxonomy....
of Poranthereae were substantially revised following phylogenetic analysis of DNA sequence
DNA sequence
The sequence or primary structure of a nucleic acid is the composition of atoms that make up the nucleic acid and the chemical bonds that bond those atoms. Because nucleic acids, such as DNA and RNA, are unbranched polymers, this specification is equivalent to specifying the sequence of...
s from members of the family Phyllanthaceae.
Within Poranthereae, groups of related
Systematics
Biological systematics is the study of the diversification of terrestrial life, both past and present, and the relationships among living things through time. Relationships are visualized as evolutionary trees...
genera are strongly correlated with habitat
Habitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...
and geographical
Physical geography
Physical geography is one of the two major subfields of geography. Physical geography is that branch of natural science which deals with the study of processes and patterns in the natural environment like the atmosphere, biosphere and geosphere, as opposed to the cultural or built environment, the...
distribution
Species distribution
Species distribution is the manner in which a biological taxon is spatially arranged. Species distribution is not to be confused with dispersal, which is the movement of individuals away from their area of origin or from centers of high population density. A similar concept is the species range. A...
. For example, Notoleptopus, Pseudophyllanthus, and Poranthera are restricted to the Old World
Old World
The Old World consists of those parts of the world known to classical antiquity and the European Middle Ages. It is used in the context of, and contrast with, the "New World" ....
Southern Hemisphere
Southern Hemisphere
The Southern Hemisphere is the part of Earth that lies south of the equator. The word hemisphere literally means 'half ball' or "half sphere"...
.
Description
Monoecious, sometimes dioeciousDioecious
Dioecy is the property of a group of biological organisms that have males and females, but not members that have organs of both sexes at the same time. I.e., those whose individual members can usually produce only one type of gamete; each individual organism is thus distinctly female or male...
herbs
Herbaceous plant
A herbaceous plant is a plant that has leaves and stems that die down at the end of the growing season to the soil level. They have no persistent woody stem above ground...
, shrub
Shrub
A shrub or bush is distinguished from a tree by its multiple stems and shorter height, usually under 5–6 m tall. A large number of plants may become either shrubs or trees, depending on the growing conditions they experience...
s, or 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...
s to 6m tall. Thorns or other armature
Armature
Armature may refer to:* Armature , the kinematic chains used in computer animation to simulate the motions of virtual characters...
absent. Stipule
Stipule
In botany, stipule is a term coined by Linnaeus which refers to outgrowths borne on either side of the base of a leafstalk...
s present, sometimes leaf-like is some Meineckia. Petioles
Petiole (botany)
In botany, the petiole is the stalk attaching the leaf blade to the stem. The petiole usually has the same internal structure as the stem. Outgrowths appearing on each side of the petiole are called stipules. Leaves lacking a petiole are called sessile, or clasping when they partly surround the...
present or absent, not pulvinate
Pulvinus
A pulvinus is a joint-like thickening at the base of a plant leaf or leaflet that facilitates growth-independent movement. It consists of a core of vascular tissue within a flexible, bulky cylinder of thin-walled parenchyma cells...
. 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....
simple, arrangement
Phyllotaxis
In botany, phyllotaxis or phyllotaxy is the arrangement of leaves on a plant stem .- Pattern structure :...
alternate, subopposite, or in some Poranthera, opposite. margins entire. 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 axillary, or rarely, apparently terminal. Flower
Flower
A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants . The biological function of a flower is to effect reproduction, usually by providing a mechanism for the union of sperm with eggs...
s solitary to fasciculate. Sepal
Sepal
A sepal is a part of the flower of angiosperms . Collectively the sepals form the calyx, which is the outermost whorl of parts that form a flower. Usually green, sepals have the typical function of protecting the petals when the flower is in bud...
s free, greenish, persistent. 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 present or absent, often partly adnate
Adnation
Adnation in plants is the "union of unlike parts; organically united or fused with another dissimilar part, e.g. an ovary to a calyx tube, or stamens to petals". This is in contrast to connation, the fusion of similar organs....
to the nectary disk, equal to the sepals or shorter, white or greenish, usually larger in staminate
Plant sexuality
Plant sexuality covers the wide variety of sexual reproduction systems found across the plant kingdom. This article describes morphological aspects of sexual reproduction of plants....
than in pistillate
Gynoecium
Gynoecium is most commonly used as a collective term for all carpels in a flower. A carpel is the ovule and seed producing reproductive organ in flowering plants. Carpels are derived from ovule-bearing leaves which evolved to form a closed structure containing the ovules...
flowers. Disk present, extrastaminal; annular
Annulus (mathematics)
In mathematics, an annulus is a ring-shaped geometric figure, or more generally, a term used to name a ring-shaped object. Or, it is the area between two concentric circles...
or divided into alternisepalous segments or glands. Stamens opposite the sepals, free or fused
Connation
Connation in plants is the developmental fusion of organs of the same type, for example, petals to one another to form a tubular corolla. This is in contrast to adnation, the fusion of dissimilar organs.-Terms for connation of flower parts:...
for up to 9/10 of their length. Anthers latrorse, at least in bud
Bud
In botany, a bud is an undeveloped or embryonic shoot and normally occurs in the axil of a leaf or at the tip of the stem. Once formed, a bud may remain for some time in a dormant condition, or it may form a shoot immediately. Buds may be specialized to develop flowers or short shoots, or may have...
, opening
Dehiscence (botany)
Dehiscence is the opening, at maturity, in a pre-defined way, of a plant structure, such as a fruit, anther, or sporangium, to release its contents. Sometimes this involves the complete detachment of a part. Structures that open in this way are said to be dehiscent...
by longitudinal slits, or in Poranthera, by pores. Ovary
Ovary (plants)
In the flowering plants, an ovary is a part of the female reproductive organ of the flower or gynoecium. Specifically, it is the part of the pistil which holds the ovule and is located above or below or at the point of connection with the base of the petals and sepals...
usually divided into three locule
Locule
A locule is a small cavity or compartment within an organ or part of an organism ....
s. Two ovule
Ovule
Ovule means "small egg". In seed plants, the ovule is the structure that gives rise to and contains the female reproductive cells. It consists of three parts: The integument forming its outer layer, the nucellus , and the megaspore-derived female gametophyte in its center...
s in each locule. Styles free to almost completely fused. 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,...
explosively dehiscent
Dehiscence (botany)
Dehiscence is the opening, at maturity, in a pre-defined way, of a plant structure, such as a fruit, anther, or sporangium, to release its contents. Sometimes this involves the complete detachment of a part. Structures that open in this way are said to be dehiscent...
. Seed
Seed
A seed is a small embryonic plant enclosed in a covering called the seed coat, usually with some stored food. It is the product of the ripened ovule of gymnosperm and angiosperm plants which occurs after fertilization and some growth within the mother plant...
s usually two per locule; sometimes one in Actephila and Meineckia.
Taxonomy
The presence and size of petals is an important character in the taxonomyPlant taxonomy
Plant taxonomy is the science that finds, describes, classifies, identifies, and names plants. It thus is one of the main branches of taxonomy.Plant taxonomy is closely allied to plant systematics, and there is no sharp boundary between the two...
of Poranthereae. In most species, the petals of staminate flowers are almost as large as the sepals, and the petals of pistillate flowers are much smaller.
Petal loss or reduction has occurred at least four times in the evolution
Introduction to evolution
Evolution is the process of change in all forms of life over generations, and evolutionary biology is the study of how evolution occurs. The biodiversity of life evolves by means of mutations, genetic drift and natural selection....
of Poranthereae. It has been observed
Empirical method
The empirical method is generally taken to mean the approach of using a collection of data to base a theory or derive a conclusion in science...
in Poranthera, Actephila, Andrachne, and Meineckia. In one species of Poranthera and in several of Actephila, the petal size is variable, and sometimes the petals are completely absent. In some species of Actephila, petal number as well as size is variable. In Andrachne subgenus
Subgenus
In biology, a subgenus is a taxonomic rank directly below genus.In zoology, a subgeneric name can be used independently or included in a species name, in parentheses, placed between the generic name and the specific epithet: e.g. the Tiger Cowry of the Indo-Pacific, Cypraea tigris Linnaeus, which...
Phyllanthidea, staminate petals are lost in some species, and pistillate petals are lost in others. Petals are entirely absent in Meineckia subgenus Meineckia.
History
The name "Poranthereae" was first used by G.R. Grüning in 1913. The type genusBiological type
In biology, a type is one particular specimen of an organism to which the scientific name of that organism is formally attached...
for the tribe is Poranthera, which was so named because the anthers open poricidally rather than by longitudinal slits.
Two similar treatments of Poranthereae were presented by Grady Webster
Grady Webster
Grady Linder Webster was a plant systematist and taxonomist. He was the recipient of a number of awards and appointed to fellowships of botanical institutions in the United States of America...
and Alan Radcliffe-Smith, in 1994 and 2001, respectively. These authors considered Poranthereae to be part of Euphorbiaceae
Euphorbiaceae
Euphorbiaceae, the Spurge family are a large family of flowering plants with 300 genera and around 7,500 species. Most are herbs, but some, especially in the tropics, are also shrubs or trees. Some are succulent and resemble cacti....
sensu lato, a taxon
Taxon
|thumb|270px|[[African elephants]] form a widely-accepted taxon, the [[genus]] LoxodontaA taxon is a group of organisms, which a taxonomist adjudges to be a unit. Usually a taxon is given a name and a rank, although neither is a requirement...
that is now known to be paraphyletic. Their circumscription of the tribe was different from that which is now generally accepted.
Poranthaceae, as currently understood, was first recognized in phylogenetic analyses of DNA sequences of selected gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
s. The existence of this clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
was not entirely unanticipated and had been at least partially suggested in several studies
Research
Research can be defined as the scientific search for knowledge, or as any systematic investigation, to establish novel facts, solve new or existing problems, prove new ideas, or develop new theories, usually using a scientific method...
based on morphology
Plant morphology
Plant morphology or phytomorphology is the study of the physical form and external structure of plants. This is usually considered distinct from plant anatomy, which is the study of the internal structure of plants, especially at the microscopic level...
. The tribe was formally established in its present form in a revision of Phyllanthaceae in 2006. In 2007, a phylogeny of Poranthereae was presented by Vorontsova et alii, based on DNA sequences of matK and ITS
Internal transcribed spacer
ITS refers to a piece of non-functional RNA situated between structural ribosomal RNAs on a common precursor transcript. Read from 5' to 3', this polycistronic rRNA precursor transcript contains the 5' external transcribed sequence , 18S rRNA, ITS1, 5.8S rRNA, ITS2, 28S rRNA and finally the 3'ETS...
. This paper included much on the taxonomic history
History of plant systematics
The history of plant systematics—the biological classification of plants—stretches from the work of ancient Greek to modern evolutionary biologists. As a field of science, plant systematics came into being only slowly, early plant lore usually being treated as part of the study of...
of the tribe.
In 2008, based on molecular phylogenetic studies, Vorontsova and Hoffmann published a revised classification of the tribe. A description of each genus and a key
Identification key
In biology, an identification key is a printed or computer-aided device that aids the identification of biological entities, such as plants, animals, fossils, microorganisms, and pollen grains...
to the genera were included. Four of the genera recognized by Radcliffe-Smith (Zimmermannia, Zimmermanniopsis, Archileptopus, and Oreoporanthera) were sunk into other genera and three new genera were established. Notoleptopus was "carved" out of Leptopus, while Pseudophyllanthus and Phyllanthopsis were removed from Andrachne.
Some of the genera in Poranthereae are still in need of revision. This is especially true of Actephila, the most variable and least understood genus in the tribe.
Phylogeny
The following phylogenetic treePhylogenetic tree
A phylogenetic tree or evolutionary tree is a branching diagram or "tree" showing the inferred evolutionary relationships among various biological species or other entities based upon similarities and differences in their physical and/or genetic characteristics...
is based on the one by Vorontsova and Hoffmann (2008). All branches have at least 75% bootstrap
Bootstrapping (statistics)
In statistics, bootstrapping is a computer-based method for assigning measures of accuracy to sample estimates . This technique allows estimation of the sample distribution of almost any statistic using only very simple methods...
support. Branches with less statistical support
Resampling (statistics)
In statistics, resampling is any of a variety of methods for doing one of the following:# Estimating the precision of sample statistics by using subsets of available data or drawing randomly with replacement from a set of data points # Exchanging labels on data points when performing significance...
are collapsed to form the tetratomy
Polytomy
A polytomy , meaning many temporal based branches, is a section of a phylogeny in which the evolutionary relationships can not be fully resolved to dichotomies. In a phylogenetic tree, a polytomy is represented as a node which has more than two immediate descending branches...
in the tree below.