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Actinidiaceae

Actinidiaceae

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Actinidiaceae, or the Chinese Gooseberry family, is a small 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...

 of plants. It includes three genera
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 and about 360 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...

. It is a member of the order Ericales
Ericales
The Ericales are a large and diverse order of dicotyledons, including for example tea, persimmon, blueberry, Brazil nut, and azalea. The order includes trees and bushes, lianas and herbaceous plants. Together with ordinary autophytic plants, the Ericales include chlorophyll-deficient...

.

Distribution


They are temperate and subtropical woody
Woody plant
A woody plant is a plant that uses wood as its structural tissue. These are typically perennial plants whose stems and larger roots are reinforced with wood produced adjacent to the vascular tissues. The main stem, larger branches, and roots of these plants are usually covered by a layer of...

 vine
Vine
A vine in the narrowest sense is the grapevine , but more generally it can refer to any plant with a growth habit of trailing or scandent, that is to say climbing, stems or runners...

s, shrubs and trees, native to Asia (Actinidia
Actinidia
Actinidia is a genus of woody and, with few exceptions, dioecious plants native to temperate eastern Asia, occurring throughout most of China, Taiwan, Korea and Japan, and extending north to southeast Siberia and south into Indochina...

 or kiwifruit, Clematoclethra
Clematoclethra
Clematoclethra Maxim. is a genus within the Actinidiaceae. It contains about 20 species and is endemic to subtropical and temperate regions of central and western China. Monophyly of the group is supported by genetic evidence and also evidence based on the cell biology of members of the genus...

, Saurauia
Saurauia
Saurauia Willd. is a genus of plant in the Actinidiaceae family. It comprises about 250 species distributed in the tropics and subtropics of Asia, and South and Central America. Genetic evidence and the cell biology of the group support monophyly of the genus...

) and Central America and South America (Saurauia
Saurauia
Saurauia Willd. is a genus of plant in the Actinidiaceae family. It comprises about 250 species distributed in the tropics and subtropics of Asia, and South and Central America. Genetic evidence and the cell biology of the group support monophyly of the genus...

only). Saurauia is with its 300 species the largest genus in this family. Although now confined to Asia and tropical Central and South America, there is evidence that in the past the family had a wider distribution. The now extinct genus Parasaurauia is thought to have belonged to the Actinidiaceae and was located in North America during the early Campanian
Campanian
The Campanian is, in the ICS' geologic timescale, the fifth of six ages of the Late Cretaceous epoch . The Campanian spans the time from 83.5 ± 0.7 Ma to 70.6 ± 0.6 Ma ...

.

Characteristics


The plants are usually small trees or shrubs, or sometimes vines (Actinidia). The alternate, simple, spiral 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....

 have serrate or entire margins. They lack 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 or are minutely stipulate. They are often beset with rather flattened bristles.

The 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 grow solitary or are aggregated in terminal cymes, with free 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 and 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. Except for members of the genus Clematoclethra
Clematoclethra
Clematoclethra Maxim. is a genus within the Actinidiaceae. It contains about 20 species and is endemic to subtropical and temperate regions of central and western China. Monophyly of the group is supported by genetic evidence and also evidence based on the cell biology of members of the genus...

which have 10 stamens, the stamen
Stamen
The stamen is the pollen producing reproductive organ of a flower...

s are numerous and originally attached at the back. They invert just before the flower starts expanding, so that their bases become apical
Apical dominance
In plant physiology, apical dominance is the phenomenon whereby the main central stem of the plant is dominant over other side stems; on a branch the main stem of the branch is further dominant over its own side branchlets....

.

The plants may be dioecious
Dioecious
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...

, monoecious or hermaphroditic
Hermaphrodite
In biology, a hermaphrodite is an organism that has reproductive organs normally associated with both male and female sexes.Many taxonomic groups of animals do not have separate sexes. In these groups, hermaphroditism is a normal condition, enabling a form of sexual reproduction in which both...

. The fruit is usually a berry
Berry
The botanical definition of a berry is a fleshy fruit produced from a single ovary. Grapes are an example. The berry is the most common type of fleshy fruit in which the entire ovary wall ripens into an edible pericarp. They may have one or more carpels with a thin covering and fleshy interiors....

, such as the edible kiwifruit
Kiwifruit
The kiwifruit, often shortened to kiwi in many parts of the world, is the edible berry of a cultivar group of the woody vine Actinidia deliciosa and hybrids between this and other species in the genus Actinidia....

, a cultivar from the genus Actinidia
Actinidia
Actinidia is a genus of woody and, with few exceptions, dioecious plants native to temperate eastern Asia, occurring throughout most of China, Taiwan, Korea and Japan, and extending north to southeast Siberia and south into Indochina...

.

Evidence supporting placement within the Ericales


Before genetic evidence appeared in the last 10 years, the placement of the Actinidiaceae within the Ericales was highly controversial. The USDA Plants Database, a resource that is considered authoritative, still places the Actinidaceae within the Theales
Theales
Theales is a botanical name at the rank of order. The name was used by the Cronquist system for an order placed in subclass Dilleniidae, in the 1981 version of the system the circumscription was:* order Theales*: family Ochnaceae*: family Sphaerosepalaceae...

, an order which has been shown not to be monophyletic. Placement of the Actinidiaceae within the Ericales has been strongly supported by genetic evidence over the past 10 years, and contrary to previous thought, it is not a basal
Basal (phylogenetics)
In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...

 member of the Ericales. Multiple studies using genetic evidence now firmly place the Actinidiaceae in the Ericoid 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...

, a monophyletic group consisting of the Ericaceae
Ericaceae
The Ericaceae, commonly known as the heath or heather family, is a group of mostly calcifuge flowering plants. The family is large, with roughly 4000 species spread across 126 genera, making it the 14th most speciose family of flowering plants...

, the Cyrillaceae
Cyrillaceae
Cyrillaceae is a small family of flowering plants in the order Ericales, native to warm temperate to tropical regions of the Americas. The family comprises two genera, each with a single species, Cyrilla racemiflora and Cliftonia monophylla....

, the Clethraceae
Clethraceae
Clethraceae is a small family of flowering plants in the order Ericales, native to warm temperate to tropical regions of Asia and the Americas, with one species also on Madeira...

, the Sarraceniaceae
Sarraceniaceae
Sarraceniaceae is a family of pitcher plants , belonging to order Ericales .The family comprises three extant genera: Sarracenia , Darlingtonia , and Heliamphora . The extinct Archaeamphora longicervia may also belong to this family...

, and the Roridulaceae. Furthermore, genetic evidence points to the Actinidiaceae being sister to the Roridulaceae, and with the Roridulaceae and Sarraceniaceae, forming another, smaller, monophyletic group.

Evidence supporting monophyly of the Actinidiaceae


What genera were to be placed in the Actinidiaceae before recent genetic and micromophological studies emerged was highly controversial. Before recent evidence, the genus Sladenia
Sladeniaceae
Sladeniaceae Airy Shaw is a family of flowering plants containing tree species found in sub-tropical to tropical environments in East Africa , Burma, Yunnan and Thailand...

 was often placed within the Actinidiaceae. Also, Saurauia
Saurauia
Saurauia Willd. is a genus of plant in the Actinidiaceae family. It comprises about 250 species distributed in the tropics and subtropics of Asia, and South and Central America. Genetic evidence and the cell biology of the group support monophyly of the genus...

was sometimes considered its own family. Thus, before 10 years ago when more detailed studies started, it was considered that there could be anywhere from 2-4 genera within the Actinidiaceae. Micromorphological characters have confirmed that Sladenia does not belong in the Actinidiaceae. Furthermore, biological characteristics of the cell
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....

s, and molecular evidence, have confirmed that the 3 genera currently circumscribed in the Actinidiaceae, the Clematoclethra
Clematoclethra
Clematoclethra Maxim. is a genus within the Actinidiaceae. It contains about 20 species and is endemic to subtropical and temperate regions of central and western China. Monophyly of the group is supported by genetic evidence and also evidence based on the cell biology of members of the genus...

, Saurauia
Saurauia
Saurauia Willd. is a genus of plant in the Actinidiaceae family. It comprises about 250 species distributed in the tropics and subtropics of Asia, and South and Central America. Genetic evidence and the cell biology of the group support monophyly of the genus...

, and Actinidia
Actinidia
Actinidia is a genus of woody and, with few exceptions, dioecious plants native to temperate eastern Asia, occurring throughout most of China, Taiwan, Korea and Japan, and extending north to southeast Siberia and south into Indochina...

do indeed form a monophyletic group.

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