Sexual dimorphism

sexually dimorphicdimorphicdimorphismsexual dichromatismsexually dichromaticsexual size dimorphismsex differencessexually monomorphicmonomorphicreverse sexual dimorphism
Sexual dimorphism is the condition where the two sexes of the same species exhibit different characteristics beyond the differences in their sexual organs.wikipedia
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biological sexsexesanatomical sex
Sexual dimorphism is the condition where the two sexes of the same species exhibit different characteristics beyond the differences in their sexual organs.
Physical differences are often associated with the different sexes of an organism; these sexual dimorphisms can reflect the different reproductive pressures the sexes experience.


Paradisaeidaebirds-of-paradisebirds of paradise
Similar examples are manifold, such as in birds of paradise and argus pheasants.
The members of this family are perhaps best known for the plumage of the males of the sexually dimorphic species (the majority), in particular the highly elongated and elaborate feathers extending from the beak, wings, tail or head.

Secondary sex characteristic

secondary sexual characteristicsecondary sex characteristicssecondary sexual characteristics
Differences may include secondary sex characteristics, size, weight, colour, markings, and may also include behavioral and cognitive differences.
These characteristics are particularly evident in the sexually dimorphic phenotypic traits that distinguish the sexes of a species, but--unlike the sex organs (primary sex characteristics)--are not directly part of the reproductive system.


eclipse plumageplumesalbinism in birds
The ornate plumage of peacocks, as used in the courting display, attracts peahens.
Many male ducks have bright, colourful plumage, exhibiting strong sexual dimorphism.

Gonepteryx rhamni

common brimstonebrimstonebrimstones
The common brimstone also displays sexual dichromatism; males have yellow and iridescent wings, while female wings are white and non-iridescent.
The adult common brimstone has sexual dimorphism in its wing coloration: males have yellow wings and iridescence while females have greenish-white wings and are not iridescent.


guppiesPoecilia reticulataguppie
For example, male guppies have colorful spots and ornamentations while females are generally grey in color.
Guppies exhibit sexual dimorphism.

Osmia bicornis

Osmia rufaRed mason bee
In Osmia rufa, for example, the female is larger/broader than males, with males being 8–10 mm in size and females being 10–12 mm in size.
Cells containing females are typically larger than those containing males, due to the sexual dimorphism of the species.

Orb-weaver spider

Araneidaeorb-weaver spidersorb weaver
In addition, female fecundity is positively correlated with female body size and large female body size is selected for, which is seen in the family Araneidae.
Sexual dimorphism refers to physical differences between males and females of the same species.

Sexual cannibalism

Canabalism during matingcannibalism before and after copulationcannibalized after mating
Size dimorphism shows a correlation with sexual cannibalism, which is prominent in spiders (it is also found in insects such as praying mantises).
Sexual cannibalism is common among species with prominent sexual size dimorphism (SSD); extreme SSD likely drove the evolution of sexual cannibalism in spiders.

Macrotera portalis

This is seen in the bee species Macrotera portalis in which there is a small-headed morph, capable of flight, and large-headed morph, incapable of flight, for males.
texana'' are not dimorphic, and nests are usually not reused for several generations.


Another example is the dragonet, in which males are considerably larger than females and possess longer fins.
Many species exhibit marked sexual dimorphism: males and females are coloured and patterned differently from each other, and (in addition to the spine filament) males have a much higher dorsal fin.


Sexual size dimorphism varies among taxa with males typically being larger, though this is not always the case, e.g. birds of prey, hummingbirds, and some species of flightless birds.
Hummingbirds exhibit sexual size dimorphism according to Rensch's rule, in which males are smaller than females in small species, and males are larger than females in large-bodied species.


Pinnipeds are known for early differential growth and maternal investment since the only nutrients for newborn pups is the milk provided by the mother.
Several species exhibit sexual dimorphism.

Ophioblennius atlanticus

redlip blenniesredlip blennyBlennophis webbii
In redlip blennies, only the male fish develops an organ at the anal-urogenital region that produces antimicrobial substances.
This organ only exists in males due to sexual dimorphism.


turtlesTestudinesTestudines indet.
The sexual dimorphism in amphibians and reptiles may be reflected in any of the following: anatomy; relative length of tail; relative size of head; overall size as in many species of vipers and lizards; coloration as in many amphibians, snakes, and lizards, as well as in some turtles; an ornament as in many newts and lizards; the presence of specific sex-related behaviour is common to many lizards; and vocal qualities which are frequently observed in frogs.
However, due to the sexual dimorphism present in most turtle species, males must develop different courting strategies or use alternate methods to gain access to a potential mate.

Asterocampa celtis

hackberry emperorAsterocampa celtis antonia
In the hackberry emperor females are similarly larger than males.
A. celtis adults exhibit sexual dimorphism.


anoleanole lizardanoles
Anole lizards show prominent size dimorphism with males typically being significantly larger than females.
In some anoles the sexes are very similar and difficult to separated under normal viewing conditions, but most species exhibit clear sexual dimorphism, which allows one to fairly easily discern between adult males and females.

Sockeye salmon

sockeyekokaneekokanee salmon
For example, in sockeye salmon, males develop larger body size at maturity, including an increase in body depth, hump height, and snout length.
There is a dramatic sexual dimorphism at maturity.


dioeciousdioecious plantdioecious plants
Most flower plants are hermaphroditic but approximately 6% of species have separate males and females (dioecy).

Nephila pilipes

Nephila maculataAranea maculatared wood spiders
Male body size is not under selection due to cannibalism in all spider species such as Nephila pilipes, but is more prominently selected for in less dimorphic species of spiders, which often selects for larger male size.
Nephila pilipes display sexual dimorphism, the presence of distinct difference between the males and females of a species.

Anthidium manicatum

European wool carder beeAnthidum manicatumwool-carder bees
Anthidium manicatum also displays male-biased sexual dimorphism.
manicatum'' are larger than females in size, displays male-biased sexual dimorphism.

Red-backed fairywren

red-backedMalurus melanocephalusred-backed fairy-wren
An example of sexual polymorphism determined by environmental conditions exists in the red-backed fairywren.
Like other fairywrens, the red-backed fairywren is notable for its marked sexual dimorphism; the male adopts full breeding plumage by the fourth year, later than all other fairywrens apart from the closely related white-winged fairywren.

Andrena agilissima

Andrena agilissima is a mining bee where the females only have a slightly larger head than the males.
The males do not show discrete size dimorphism unlike other bees and all are able to fly.

Lamprologus callipterus

Neolamprologus callipterus
An example is Lamprologus callipterus, a type of cichlid fish.
These fish exhibit strong sexual dimorphism.


Sexual dimorphism is maintained by the counteracting pressures of natural selection and sexual selection.
The phenotypic difference between males and females is called sexual dimorphism.