A sexual system is a pattern of

sex allocation Sex is the trait that determines whether a sexually reproducing animal or plant produces male or female gametes. Male plants and animals produce smaller mobile gametes (spermatozoa, sperm, pollen), while females produce larger ones (ova, oft ...

or a distribution of

male Male (symbol: ♂) is the sex of an organism that produces the gamete (sex cell) known as sperm, which fuses with the larger female gamete, or ovum, in the process of fertilization. A male organism cannot reproduce sexually without access to ...

and

female Female (Venus symbol, symbol: ♀) is the sex of an organism that produces the large non-motile ovum, ova (egg cells), the type of gamete (sex cell) that fuses with the Sperm, male gamete during sexual reproduction. A female has larger gamet ...

function across organisms in a species. Terms like reproductive system and mating system have also been used as synonyms. The distinction between sexual systems is not always clear due to

phenotypic plasticity Phenotypic plasticity refers to some of the changes in an organism's behavior, morphology and physiology in response to a unique environment. Fundamental to the way in which organisms cope with environmental variation, phenotypic plasticity encompa ...

. Sexual systems are viewed as a key factor for

genetic variation Genetic variation is the difference in DNA among individuals or the differences between populations. The multiple sources of genetic variation include mutation and genetic recombination. Mutations are the ultimate sources of genetic variation, ...

and

reproductive success Reproductive success is an individual's production of offspring per breeding event or lifetime. This is not limited by the number of offspring produced by one individual, but also the reproductive success of these offspring themselves. Reproduct ...

, and may have also led to the origin or

extinction Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

of certain

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

. Interests in sexual systems go back to Darwin, who found that

barnacle A barnacle is a type of arthropod constituting the subclass Cirripedia in the subphylum Crustacea, and is hence related to crabs and lobsters. Barnacles are exclusively marine, and tend to live in shallow and tidal waters, typically in eros ...

s contain species that are

androdioecious Androdioecy is a reproductive system characterized by the coexistence of males and hermaphrodites. Androdioecy is rare in comparison with the other major reproductive systems: dioecy, gynodioecy and hermaphroditism. In animals, androdioecy has bee ...

and some that are

dioecious Dioecy (; ; adj. dioecious , ) is a characteristic of a species, meaning that it has distinct individual organisms (unisexual) that produce male or female gametes, either directly (in animals) or indirectly (in seed plants). Dioecious reproductio ...

Types of sexual systems

In plants there are monomorphic sexual systems where a species has

hermaphrodite In reproductive biology, a hermaphrodite () is an organism that has both kinds of reproductive organs and can produce both gametes associated with male and female sexes. Many Taxonomy (biology), taxonomic groups of animals (mostly invertebrate ...

and/or

flower A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants (plants of the division Angiospermae). The biological function of a flower is to facilitate reproduction, usually by providing a mechani ...

s on the same plant. Monomorphic sexual systems include

monoecy Monoecy (; adj. monoecious ) is a sexual system in seed plants where separate male and female cones or flowers are present on the same plant. It is a monomorphic sexual system alongside gynomonoecy, andromonoecy and trimonoecy. Monoecy is conne ...

gynomonoecy Gynomonoecy is defined as the presence of both female and hermaphrodite flowers on the same individual of a plant species. It is prevalent in Asteraceae but is poorly understood. It is a monomorphic sexual system alongside monoecy, andromonoecy ...

andromonoecy Andromonoecy is a breeding system of plant species in which male and hermaphrodite flowers are on the same plant. It is a monomorphic sexual system alongside monoecy, gynomonoecy and trimonoecy. Andromonoecy is frequent among genera with zygomorp ...

and trimonoecy. There are also dimorphic sexual systems like

dioecy Dioecy (; ; adj. dioecious , ) is a characteristic of a species, meaning that it has distinct individual organisms (unisexual) that produce male or female gametes, either directly (in animals) or indirectly (in seed plants). Dioecious reproductio ...

gynodioecy Gynodioecy is a rare breeding system that is found in certain flowering plant species in which female and hermaphroditic plants coexist within a population. Gynodioecy is the evolutionary intermediate between hermaphroditism (exhibiting both fem ...

and

androdioecy Androdioecy is a reproductive system characterized by the coexistence of males and hermaphrodites. Androdioecy is rare in comparison with the other major reproductive systems: dioecy, gynodioecy and hermaphroditism. In animals, androdioecy has bee ...

. Mixed sexual systems are where

s coexist with single sexed individuals. This includes androdioecy, gynodioecy, and

trioecy Trioecy, or subdioecy, is a rare sexual system characterized by the coexistence of males, females, and hermaphrodites. It has been found in both plants and animals. Trioecy is sometimes referred to as a mixed mating system alongside androdioecy an ...

List of sexual systems

A

Androdioecy

Androdioecy Androdioecy is a reproductive system characterized by the coexistence of males and hermaphrodites. Androdioecy is rare in comparison with the other major reproductive systems: dioecy, gynodioecy and hermaphroditism. In animals, androdioecy has bee ...

is a sexual system in which males and hermaphrodites coexist in a population. It is rare in both plants and animals.

Andromonoecy

Andromonoecy Andromonoecy is a breeding system of plant species in which male and hermaphrodite flowers are on the same plant. It is a monomorphic sexual system alongside monoecy, gynomonoecy and trimonoecy. Andromonoecy is frequent among genera with zygomorp ...

is a rare sexual system in

angiosperms 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 ...

, in which a plant has both male and hermaphroditic flowers. It has been a subject of interest regarding the mechanism of sex expression.

D

Dioicy

Dioicy Dioicy () is a sexual system where archegonia and antheridia are produced on separate gametophytes. It is one of the two main sexual systems in bryophytes. Both dioicous () and monoicous gametophytes produce gametes in gametangia by mitosis ra ...

is one of the two main sexual systems in

bryophyte The Bryophyta s.l. are a proposed taxonomic division containing three groups of non-vascular land plants (embryophytes): the liverworts, hornworts and mosses. Bryophyta s.s. consists of the mosses only. They are characteristically limited in ...

s. In dioicy male and female sex organs are on separate

gametophyte A gametophyte () is one of the two alternation of generations, alternating multicellular organism, multicellular phases in the life cycles of plants and algae. It is a haploid multicellular organism that develops from a haploid spore that has on ...

Dioecy

Dioecy Dioecy (; ; adj. dioecious , ) is a characteristic of a species, meaning that it has distinct individual organisms (unisexual) that produce male or female gametes, either directly (in animals) or indirectly (in seed plants). Dioecious reproductio ...

is a sexual system in which a species has distinct individual organisms that are either male or female, i.e., they produce only male or only female gametes, either directly (in animals) or indirectly (in plants).

G

Gonochorism

Gonochorism In biology, gonochorism is a sexual system where there are only two Sex, sexes and each individual organism is either male or female. The term gonochorism is usually applied in animal species, the vast majority of which are gonochoric. Gonochor ...

is a sexual system where individuals are either male or female. The term "gonochorism" is usually applied to animals while "dioecy" is applied to plants. Gonochorism is the most common sexual system in animals, occurring in 95% of animal species.

Gynodioecy

Gynodioecy Gynodioecy is a rare breeding system that is found in certain flowering plant species in which female and hermaphroditic plants coexist within a population. Gynodioecy is the evolutionary intermediate between hermaphroditism (exhibiting both fem ...

is a sexual system in which females and hermaphrodites coexist in the same population.

Gynomonoecy

Gynomonoecy Gynomonoecy is defined as the presence of both female and hermaphrodite flowers on the same individual of a plant species. It is prevalent in Asteraceae but is poorly understood. It is a monomorphic sexual system alongside monoecy, andromonoecy ...

is defined as the presence of both

and

flowers on the same individual of a plant species. It is prevalent in

Asteraceae The family Asteraceae, alternatively Compositae, consists of over 32,000 known species of flowering plants in over 1,900 genera within the order Asterales. Commonly referred to as the aster, daisy, composite, or sunflower family, Compositae w ...

but is poorly understood.

Gynodioecy-Gynomonoecy

Gynodioecy-Gynomonoecy is a sexual system for plants when female, hermaphrodite, and gynomonoecious plants coexist in the same population.

M

Monoicy

Monoicy Monoicy () is a sexual system in haploid plants (mainly bryophytes) where both sperm and eggs are produced on the same gametophyte, in contrast with dioicy, where each gametophyte produces only sperm or eggs but never both.Crandall-Stotler, B.J ...

is one of the two main sexual systems in

s. In monoicy male and female sex organs are present in the same

Monoecy

Monoecy Monoecy (; adj. monoecious ) is a sexual system in seed plants where separate male and female cones or flowers are present on the same plant. It is a monomorphic sexual system alongside gynomonoecy, andromonoecy and trimonoecy. Monoecy is conne ...

is a sexual system in which male and female flowers are present on the same plant. It is common in

, and occurs in 10% of all plant species.

S

Sequential hermaphroditism

sequential hermaphroditism Sequential hermaphroditism (called dichogamy in botany) is a type of hermaphroditism that occurs in many fish, gastropods, and plants. Sequential hermaphroditism occurs when the individual changes its sex at some point in its life. In particular, ...

individuals start their adult lives as one sex, and change to the other sex at a later age.

Sequential monoecy

Sequential monoecy is a considered a confusing sexual system. Sequential monoecy can be difficult to differentiate from dioecy.

Simultaneous hermaphroditism

Simultaneous hermaphroditism Simultaneous hermaphroditism is one of the two types of Hermaphrodite, hermaphroditism, the other type being sequential hermaphroditism. In this form of hermaphroditism an individual has Sex organ, sex organs of both Sex, sexes and can produce bo ...

is a sexual system where an individual can produce both gamete types in the same breeding season. Simultaneous hermaphroditism is one of the most common sexual systems in animals (though far less common than

gonochorism In biology, gonochorism is a sexual system where there are only two Sex, sexes and each individual organism is either male or female. The term gonochorism is usually applied in animal species, the vast majority of which are gonochoric. Gonochor ...

) and is one of the most stable.

Synoecy

Synoecy is a sexual system in which all individuals in a population of flowering plants bear solely hermaphrodite flowers.

T

Trioecy

Trioecy Trioecy, or subdioecy, is a rare sexual system characterized by the coexistence of males, females, and hermaphrodites. It has been found in both plants and animals. Trioecy is sometimes referred to as a mixed mating system alongside androdioecy an ...

is a sexual system where males, females, and hermaphrodites exist in the same population. It is present in both plants and animals but is always extremely rare. Trioecy occurs in about 3.6% of flowering plants.

Trimonoecy

Trimonoecy Trimonoecy, also called polygamomonoecious, is when male, female, and hermaphrodite flowers are on the same plant. Trimonoecy is rare. It is a monomorphic sexual system along with monoecy, gynomonoecy, and andromonoecy. It is hypothesized that t ...

(also called androgynomonoecy) is when male, female, and hermaphrodite flowers are present on the same plant. Triomonoecy is rare.

References

{{Reflist Sex Reproduction Developmental biology Sexual system Evolutionary biology Taxonomy (biology)