Ants have a haplodiploid sex-determination system, where females are diploid and develop from fertilized eggs (sexually) and males are haploid and develop from unfertilized eggs (arrhenotokous parthenogenesis). However, a handful of ant species can produce female offspring parthenogenetically. In these, asexual reproduction produces a diploid embryo which develops from an unfertilized egg (thelytokous parthenogensis). Facultative parthenogenesis occurs when a female can produce offspring either sexually or asexually, although this ability is extremely rare.
With thelytoky, female offspring may or may not be complete clones of their mothers, depending on the type of parthenogenesis that takes place (automixis or apomixis) (Fournier et al., 2005; Rabling & Kronauer, 2013), and these offspring can develop into either queens or workers. Examples of such species included Mycocepurus smithii and clonal raider ant, Ooceraea biroi.
The workers in some species and the queens in others are known to reproduce by parthenogenesis. In Cataglyphis cursor, a European formicine ant, queens and workers can produce new queens by parthenogenesis while workers are produced sexually (Pearcy et al., 2004).
In Central and South American little fire ants, Wasmannia auropunctata, queens produce more queens through automictic parthenogenesis with central fusion. Sterile workers are usually produced from fertilized eggs. In some of the eggs fertilized by males, however, the fertilization can cause the female genetic material to be ablated from the zygote. In this way, males pass on only their genes to become fertile male offspring. This is the first recognized example of an animal species where both females and males can reproduce clonally resulting in a complete separation of male and female gene pools (Fournier et al., 2005). As a consequence, the males will only have fathers and the queens only mothers, while the sterile workers are the only ones with parents of both genders.
These ants get the benefits of both asexual and sexual reproduction - the daughters who can reproduce (the queens) have all of the mother's genes, while the sterile workers whose physical strength and disease resistance are important are produced sexually.
Reproductive strategy can vary across populations within a single species. Workers of Platythyrea punctata from the Caribbean are fully capable of parthenogenesis and produce diploid female offspring from unfertilized eggs, and mated females and males are rare. In contrast, workers in one colony from Costa Rica were incapable of thelytoky; instead mated workers produced all female offspring while the northernmost population from Texas show sexual reproduction, and individuals were incapable of reproduction by thelytoky (Kellner et al., 2013).
Taxa Known to be Parthenogenetic
Subfamily placement (in red) of species known to reproduce using parthenogenesis.
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