page_title: Sexual mimicry
section_title: Genetic control over sexual mimicry
hierarchical_section_title: Sexual mimicry / Genetic control over sexual mimicry
caption_attribution_description: English: An illustration showing the relative sizes and shapes of the different forms of Paracerceis sculpta
context_page_description: Sexual mimicry occurs when one sex mimics the opposite sex in its behavior, appearance, or chemical signalling. It is more commonly seen within invertebrate species, although sexual mimicry is also seen among vertebrates such as spotted hyenas. Sexual mimicry is commonly used as a mating strategy to gain access to a mate, a defense mechanism to avoid more dominant individuals, or a survival strategy. It can also be a physical characteristic that establishes an individual's place in society. Sexual mimicry is employed differently across species and it is part of their strategy for survival and reproduction. Examples of sexual mimicry in animals include the spotted hyena, certain types of fish, passerine birds and some species of insect among others. These are cases of intraspecific sexual mimicry, but interspecific sexual mimicry can also occur in some plant species, especially orchids. In plants employing sexual mimicry, flowers mimic mating signals of their pollinator insects. These insects are attracted and pollinate the flowers through pseudocopulations or other sexual behaviors performed on the flower.
context_section_description: Some organisms’ sexual mimicry is genetically determined by specific alleles. Unlike sexual mimicry that arises due to molecular compounds or hormones and can sometimes be induced through these molecules, this sexual mimicry arises from the organism's genetic material. Besides the female hyenas’ sexual anatomy, which is part of their genetics, some other organisms have only some males/females in their population who look like the opposite sex and this is determined by specific alleles.
  In the marine isopod population, Paracerceis sculpta, there are three different male morphologies: the alpha male is the largest morph, it matures last, and it is the one who gets privileged access to the females. The beta male is of intermediate size, and it mimics the female to get access to females. Last, the gamma male is the smallest morph and it invades harems, where females go to mate with alpha males, for mating opportunities. This morphology is associated with a single autosomal gene and three different alleles. Beta is the most dominant allele, followed by gamma, which is followed by alpha.  Selection on these alleles acts according to the Hardy-Weinberg equilibrium and mating success is equivalent among all three morphs.
  The alpha males, who are homozygous for the alpha allele, mate with many females in a harem. The females prefer to aggregate with other females in the harem, which gives the alpha male a bigger selection of mating partners. Shuster (1992) looked at the behaviour and relationship of each morph with respect to the harem and found that beta and gamma males could locate harems that have sexually receptive females. They were also able to differentiate between a harem with a sexually receptive female, i.e. one that is able to mate, and a non-sexually receptive female, i.e. one that has already deposited the embryo into her pouch and can no longer mate. While it is still unclear how the beta males do this or how their mating strategies work, they are not harassed by alpha males due to their mimicry of females: the beta males can attract other females into the harem since females like to go where other females are, and this provides the alpha males with more mates.
  Another order of organisms whose sexual mimicry is influenced by their DNA is the Odonata, carnivorous insects known as dragonflies and damselflies. In these species, it is the female who sometimes mimics the male. Within a species, groups of females will differ in colour: one group mimics the males’ colour and they are known as androchromes. Other groups will have their own female colouration and they are known as gynochromes. In Ischnura elegans, androchromes comprise 6-30% of the female population and their colour is usually blue, like the males; in some populations, androchromes are larger in size than gynochromes. This polymorphism is controlled by an autosomal allele and some studies have looked at the reason for the polymorphism's maintenance.
  The most likely theory for the  maintenance of the polymorphism in Odonata is the density dependence theory  that states that at a high male density, the androchromes are not bothered by the males and their existence is not threatened by male harassment. This hypothesis also assumes that males cannot distinguish between androchromes and other males. This advantage, however, is counteracted with the fact that they will not get a lot of mating opportunities (if any) and their reproduction is limited. This theory is the most likely explanation for the maintenance of polymorphism, since studies have shown that there is an advantage for androchromes in high male-density populations.
caption: Paracerceis sculpta (Marine isopod)
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