''Platythyrea'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of predaceous

ant Ants are Eusociality, eusocial insects of the Family (biology), family Formicidae and, along with the related wasps and bees, belong to the Taxonomy (biology), order Hymenoptera. Ants evolved from Vespoidea, vespoid wasp ancestors in the Cre ...

s in the

subfamily In biological classification, a subfamily (Latin: ', plural ') is an auxiliary (intermediate) taxonomic rank, next below family but more inclusive than genus. Standard nomenclature rules end botanical subfamily names with "-oideae", and zo ...

Ponerinae Ponerinae, the ponerine ants, is a subfamily of ants in the Poneromorph subfamilies group, with about 1,600 species in 47 extant genera, including '' Dinoponera gigantea'' - one of the world's largest species of ant. Mated workers have replac ...

and the sole member of the

tribe The term tribe is used in many different contexts to refer to a category of human social group. The predominant worldwide use of the term in English is in the discipline of anthropology. The definition is contested, in part due to conflict ...

Platythyreini.

Distribution

The genus has a worldwide distribution, and is found in the

tropics The tropics are the regions of Earth surrounding the equator, where the sun may shine directly overhead. This contrasts with the temperate or polar regions of Earth, where the Sun can never be directly overhead. This is because of Earth's ax ...

and

subtropics The subtropical zones or subtropics are geographical and climate zones immediately to the north and south of the tropics. Geographically part of the temperate zones of both hemispheres, they cover the middle latitudes from to approximately ...

of the world.

Description

Workers are small to very large in size (4–20 mm). Gamergates (reproductive female workers) are known from all studied species except one, ''P. conradti'', which have

ergatoid An ergatoid (from Greek '' ergat-'', "worker" + '' -oid'', "like") is a permanently wingless reproductive adult ant or termite. The similar but somewhat ambiguous term ergatogyne refers to any intermediate form between workers and standard gyne ...

queens (wingless reproductive ants, intermediate in form between workers and winged queens). Some species with gamergates also have

alate Alate (Latin ''ālātus'', from ''āla'' (“wing”)) is an adjective and noun used in entomology and botany to refer to something that has wings or winglike structures. In entomology In entomology, "alate" usually refers to the winged form of ...

queens, which are similar to the workers but winged. Central fusion and terminal fusion automixis

Parthenogenesis

Parthenogenesis is a natural form of reproduction in which growth and development of

embryo An embryo ( ) is the initial stage of development for a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male sp ...

s occur without

fertilisation Fertilisation or fertilization (see spelling differences), also known as generative fertilisation, syngamy and impregnation, is the fusion of gametes to give rise to a zygote and initiate its development into a new individual organism or of ...

Thelytoky Thelytoky (from the Ancient Greek, Greek θῆλυς ''thēlys'' "female" and τόκος ''tókos'' "birth") is a type of parthenogenesis and is the absence of mating and subsequent production of all female diploid offspring as for example in aph ...

is a particular form of parthenogenesis in which the development of a female individual occurs from an unfertilized egg. Automixis is a form of thelytoky, but there are different kinds of automixis. The kind of automixis relevant here is one in which two haploid products from the same

meiosis Meiosis () is a special type of cell division of germ cells in sexually-reproducing organisms that produces the gametes, the sperm or egg cells. It involves two rounds of division that ultimately result in four cells, each with only one c ...

combine to form a

diploid Ploidy () is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes. Here ''sets of chromosomes'' refers to the number of maternal and paternal chromosome copies, ...

zygote A zygote (; , ) is a eukaryote, eukaryotic cell (biology), cell formed by a fertilization event between two gametes. The zygote's genome is a combination of the DNA in each gamete, and contains all of the genetic information of a new individ ...

(see diagram). Colonies of ''Platythyrea punctata'' from Florida and the Caribbean Islands produce offspring almost exclusively by automictic thelytoky. Automixis appears to involve central fusion of two of the haploid products of meiosis (see diagram). This form of automixis tends to maintain

heterozygosity Zygosity (the noun, zygote, is from the Greek "yoked," from "yoke") () is the degree to which both copies of a chromosome or gene have the same genetic sequence. In other words, it is the degree of similarity of the alleles in an organism. Mos ...

in transmission of the genome from mother to offspring, and to minimize

inbreeding depression Inbreeding depression is the reduced biological fitness caused by loss of genetic diversity as a consequence of inbreeding, the breeding of individuals closely related genetically. This loss of genetic diversity results from small population siz ...

. Furthermore, crossover recombination occurs at a greatly reduced rate during

, which likely restrains the transition from heterozygosity to homozygosity.

Species

References

External links

* Ponerinae Ant genera {{Ponerinae-stub