Editing Asexual reproduction

{{Short description|Reproduction without a sexual process}}
{{Distinguish|Asexuality}}
{{pp-pc|small=yes}}
{{Use dmy dates|date=July 2020}}
[[File:caduco.jpg|thumb|Asexual reproduction in [[Marchantiophyta|liverworts]]: a [[dehiscence (botany)|caducous]] [[leaf|phylloid]] germinating]]
'''Asexual reproduction''' is a type of [[reproduction]] that does not involve the fusion of [[gamete]]s or change in the number of [[chromosomes]]. The offspring that arise by asexual reproduction from either unicellular or [[multicellular organism]]s inherit the full set of genes of their single parent and thus the newly created individual is genetically and physically similar to the parent or an exact clone of the parent. Asexual reproduction is the primary form of reproduction for [[single-celled organism]]s such as [[archaea]] and [[eubacteria|bacteria]]. Many [[Eukaryote|eukaryotic]] organisms including [[plant]]s, [[animal]]s, and [[Fungus|fungi]] can also reproduce asexually.<ref>{{cite journal |last1=Engelstädter |first1=Jan |title=Asexual but Not Clonal: Evolutionary Processes in Automictic Populations |journal=Genetics |date=June 2017 |volume=206 |issue=2 |pages=993–1009 |doi=10.1534/genetics.116.196873 |pmid=28381586 |pmc=5499200 }}</ref> In [[Vertebrate|vertebrates]], the most common form of asexual reproduction is [[parthenogenesis]], which is typically used as an alternative to sexual reproduction in times when reproductive opportunities are limited. Some [[Monitor lizard|monitor lizards]], including [[Komodo dragon]]s, can reproduce asexually.<ref name="Dudgeon-2017">{{cite journal |last1=Dudgeon |first1=Christine L. |last2=Coulton |first2=Laura |last3=Bone |first3=Ren |last4=Ovenden |first4=Jennifer R. |last5=Thomas |first5=Severine |title=Switch from sexual to parthenogenetic reproduction in a zebra shark |journal=Scientific Reports |date=16 January 2017 |volume=7 |issue=1 |page=40537 |doi=10.1038/srep40537 |pmid=28091617 |pmc=5238396 |bibcode=2017NatSR...740537D }}</ref>

While all [[prokaryote]]s reproduce without the formation and fusion of gametes, mechanisms for [[lateral gene transfer]] such as [[Bacterial conjugation|conjugation]], [[Transformation (genetics)|transformation]] and [[Transduction (genetics)|transduction]] can be likened to [[sexual reproduction]] in the sense of [[genetic recombination]] in [[meiosis]].<ref name="Narra-2006">{{cite journal |author1=Narra, H. P. |author2=Ochman, H.  |title=Of what use is sex to bacteria? |journal=Current Biology |year=2006 |volume=16 |pages=R705–710 |pmid=16950097 |doi=10.1016/j.cub.2006.08.024 |issue=17 |doi-access=free |bibcode=2006CBio...16.R705N }}</ref><ref>{{cite news |last1=Bryner |first1=Jeanna |title=Female Komodo Dragon Has Virgin Births |url=https://www.livescience.com/9460-female-komodo-dragon-virgin-births.html |work=Live Science |date=20 December 2006 }}</ref>

==Types of asexual reproduction==

===Fission===
{{main|Fission (biology)}}

[[Prokaryote]]s ([[Archaea]] and [[Bacteria]]) reproduce asexually through [[Fission (biology)|binary fission]], in which the parent organism divides in two to produce two genetically identical daughter organisms. [[Eukaryote]]s (such as [[protist]]s and unicellular [[fungi]]) may reproduce in a functionally similar manner by [[mitosis]]; most of these are also capable of sexual reproduction.

Multiple fission at the cellular level occurs in many [[protist]]s, e.g. [[sporozoa]]ns and [[algae]]. The [[cell nucleus|nucleus]] of the parent cell divides several times by [[mitosis]], producing several nuclei. The cytoplasm then separates, creating multiple [[daughter cells]].<ref name="E-Britannica">{{cite encyclopedia |url=https://www.britannica.com/EBchecked/topic/498542/reproduction/76146/Multiple-fission |title=Cell reproduction |encyclopedia=Encyclopædia Britannica}}</ref><ref name="Britannica-2011">{{cite book |author=Britannica Educational Publishing |title=Fungi, Algae, and Protists |publisher=The Rosen Publishing Group |year=2011 |isbn=978-1-61530-463-9 |url=https://books.google.com/books?id=_U9MB4iUpDIC&q=multiple%20fission&pg=PA101}}</ref><ref name="Puranik-2007">{{cite book |author=P.Puranik |author2=Asha Bhate |title=Animal Forms And Functions: Invertebrata |publisher=Sarup & Sons |year=2007 |isbn=978-81-7625-791-6 |url=https://books.google.com/books?id=-kdq6RyyVE0C&q=multiple%20fission&pg=PA87}}</ref>

In [[apicomplexa]]ns, multiple fission, or [[schizogony]] appears either as [[protozoal merogony|merogony]], [[sporogony]] or [[gametogony]]. Merogony results in [[merozoite]]s, which are multiple daughter cells, that originate within the same cell membrane,<ref name="Margulis-2001">{{cite book |author1=Margulis, Lynn |author1-link=Lynn Margulis |author2=McKhann, Heather I. |author3=Olendzenski, Lorraine |title=Illustrated glossary of protoctista: vocabulary of the algae, apicomplexa, ciliates, foraminifera, microspora, water molds, slime molds, and the other protoctists |publisher=Jones & Bartlett learn |year=2001 |url=https://books.google.com/books?id=y55Efu3baksC&q=Merogony%20multiple%20division&pg=PA72 |isbn=978-0-86720-081-2}}</ref><ref name="Tanada-1993">{{cite book |author1=Yoshinori Tanada |author2=Harry K. Kaya |title=Insect pathology |publisher=Gulf Professional Publishing |year=1993 |isbn=978-0-12-683255-6 |url=https://books.google.com/books?id=99YwOQnsgGUC&q=difference%20between%20merogony%20and%20schizogony&pg=PA415}}</ref> sporogony results in [[sporozoite]]s, and gametogony results in micro[[gamete]]s.

===Budding===
{{main|Budding}}
[[File:S cerevisiae under DIC microscopy.jpg|thumb|The yeast ''[[Saccharomyces cerevisiae]]'' reproducing by [[budding]]]]

Some cells divide by [[budding]] (for example [[Saccharomyces cerevisiae|baker's yeast]]), resulting in a "mother" and a "daughter" cell that is initially smaller than the parent. Budding is also known on a multicellular level; an animal example is the [[Hydra (genus)|hydra]],<ref>{{cite journal |last1=Leeuwenhoek |first1=Antoni Van |title=IV. Part of a letter from Mr Antony van Leeuwenhoek, F. R. S. concerning green weeds growing in water, and some animalcula found about them. |journal=Philosophical Transactions of the Royal Society of London |date=February 1703 |volume=23 |issue=283 |pages=1304–1311 |doi=10.1098/rstl.1702.0042 }}</ref> which reproduces by budding. The buds grow into fully matured individuals which eventually break away from the parent organism.

Internal budding is a process of asexual reproduction, favoured by parasites such as ''[[Toxoplasma gondii]]''. It involves an unusual process in which two (''endodyogeny'') or more (''endopolygeny'') daughter cells are produced inside a mother cell, which is then consumed by the offspring prior to their separation.<ref name="Smyth-1994">{{cite book |author1=Smyth, James Desmond |author2=Wakelin, Derek |title=Introduction to animal parasitology |year=1994 |publisher=Cambridge University Press |pages=101–102 |edition=3 |isbn=978-0-521-42811-8 }}</ref>

Also, budding (external or internal) occurs in some worms like ''[[Taenia (flatworm)|Taenia]]'' or ''[[Echinococcus]]''; these worms produce cysts and then produce (invaginated or evaginated) [[protoscolex]] with [[budding]].

===Vegetative propagation===
{{main|Vegetative propagation}}
[[File:Bryophyllum daigremontianum nahaufnahme1.jpg|thumb|Vegetative plantlets of mother-of-thousands, ''[[Bryophyllum daigremontianum|Bryophyllum daigremontianum (Kalanchoe daigremontiana)]]'']]

[[Vegetative propagation]] is a type of asexual reproduction found in plants where new individuals are formed without the production of seeds or spores and thus without [[syngamy]] or [[meiosis]].<ref>{{cite web |url=http://www.ucmp.berkeley.edu/glossary/gloss6/asexual.html |title=Asexual Reproduction |publisher=Ucmp.berkeley.edu |access-date=13 August 2010}}</ref> Examples of vegetative reproduction include the formation of miniaturized plants called plantlets on specialized leaves, for example in kalanchoe (''[[Bryophyllum daigremontianum]]'') and many produce new plants from [[rhizome]]s or [[stolon]] (for example in [[Garden strawberry|strawberry]]). Some plants reproduce by forming [[bulb]]s or [[tuber]]s, for example [[tulip]] bulbs and ''[[Dahlia]]'' tubers. In these examples, all the individuals are clones, and the clonal population may cover a large area.<ref>{{cite web |url=http://www.fs.fed.us/wildflowers/communities/aspen/grow.shtml |title=Celebrating Wildflowers – Fading Gold – How Aspens Grow |publisher=Fs.fed.us |date=11 May 2010 | archive-url= https://web.archive.org/web/20100923073834/http://www.fs.fed.us/wildflowers/communities/aspen/grow.shtml | archive-date= 23 September 2010  | url-status= live}}</ref>

===Spore formation===
{{main|Sporogenesis}}
Many multicellular organisms produce [[spore]]s during their [[biological life cycle]] in a process called ''sporogenesis''. Exceptions are animals and some protists, which undergo ''meiosis'' immediately followed by fertilization. Plants and many algae on the other hand undergo ''sporic meiosis'' where meiosis leads to the formation of [[haploid]] spores rather than gametes. These spores grow into multicellular individuals called [[gametophyte]]s, without a fertilization event. These haploid individuals produce [[gamete]]s through [[mitosis]]. Meiosis and gamete formation therefore occur in separate multicellular generations or "phases" of the life cycle, referred to as [[alternation of generations]]. Since sexual reproduction is often more narrowly defined as the fusion of gametes ([[fertilization]]), spore formation in plant [[sporophyte]]s and algae might be considered a form of asexual reproduction (agamogenesis) despite being the result of [[meiosis]] and undergoing a reduction in [[ploidy]]. However, both events (spore formation and fertilization) are necessary to complete sexual reproduction in the plant life cycle.

Fungi and some algae can also utilize true asexual [[spore]] formation, which involves [[mitosis]] giving rise to reproductive cells called mitospores that develop into a new organism after dispersal. This method of reproduction is found for example in [[Conidium|conidial fungi]] and the [[red algae]] ''Polysiphonia'', and involves sporogenesis without meiosis. Thus the chromosome number of the spore cell is the same as that of the parent producing the spores. However, mitotic sporogenesis is an exception and most spores, such as those of plants and many algae, are produced by [[meiosis]].<ref>"Plant." ''Britannica Academic'', Encyclopædia Britannica, 15 Jun. 2021. Accessed 20 Jan. 2022.</ref><ref>Card, V. (2016). Algae. In M. S. Hill (Ed.), ''Biology'' (2nd ed., Vol. 1, pp. 21–23). Macmillan Reference USA.</ref><ref>"Fungus." ''Britannica Academic'', Encyclopædia Britannica, 4 Oct. 2018. Accessed 20 Jan. 2022.</ref>

===Fragmentation===
[[File:Tu - Linckia guildingi cropped.jpg|thumb |right |alt=Regeneration from an arm |''[[Linckia guildingi]]'' "comet", a [[starfish]] regrowing from a single arm]]
{{main|Fragmentation (reproduction)}}

Fragmentation is a form of asexual reproduction where a new organism grows from a fragment of the parent. Each fragment develops into a mature, fully grown individual. Fragmentation is seen in many organisms. Animals that reproduce asexually include [[planarian]]s, many [[annelid]] worms including [[polychaete]]s<ref name="Ruppert-2004">{{cite book | author1=Ruppert, E. E. | author2=Fox, R. S. | author3=Barnes, R. D. | title=Invertebrate Zoology | chapter=Annelida | publisher=Brooks / Cole | edition=7 | isbn=978-0-03-025982-1 | year=2004 | pages=[https://archive.org/details/isbn_9780030259821/page/434 434–441] | url=https://archive.org/details/isbn_9780030259821/page/434 }}</ref> and some [[oligochaete]]s,<ref name="Ruppert-2004"/> [[turbellarians]] and [[sea stars]]. Many fungi and plants reproduce asexually. Some plants have specialized structures for reproduction via fragmentation, such as ''[[Gemma (botany)|gemmae]]'' in [[mosses]] and [[Marchantiophyta|liverworts]]. Most [[lichen]]s, which are a [[Symbiosis|symbiotic]] union of a fungus and [[Photosynthesis|photosynthetic]] algae or [[cyanobacteria]], reproduce through fragmentation to ensure that new individuals contain both symbionts. These fragments can take the form of ''soredia'', dust-like particles consisting of fungal hyphae wrapped around photobiont cells.

Clonal Fragmentation in multicellular or colonial organisms is a form of asexual reproduction or cloning where an organism is split into fragments. Each of these fragments develop into mature, fully grown individuals that are clones of the original organism. In [[echinoderm]]s, this method of reproduction is usually known as ''fissiparity''.<ref name="Skold-2009">{{cite book |author1=Sköld, Helen Nilsson |author2=Obst, Matthias |author3=Sköld, Mattias |author4=Åkesson, Bertil |editor1=Baruch Rinkevich |editor2=Valeria Matranga |title=Stem Cells in Marine Organisms |chapter=Stem Cells in Asexual Reproduction of Marine Invertebrates |publisher=Springer |year=2009 |page=125 |isbn=978-90-481-2766-5 |chapter-url=https://books.google.com/books?id=-eP2p0VF6VcC&q=Fissiparity&pg=PA125}}</ref> Due to many environmental and [[Epigenetics|epigenetic]] differences, clones originating from the same ancestor might actually be genetically and epigenetically different.<ref>{{cite journal |last1=Neuhof |first1=Moran |last2=Levin |first2=Michael |last3=Rechavi |first3=Oded |title=Vertically and horizontally-transmitted memories – the fading boundaries between regeneration and inheritance in planaria |journal=Biology Open |date=26 August 2016 |pages=1177–1188 |doi=10.1242/bio.020149 |pmid=27565761 |pmc=5051648 |volume=5|issue=9 }}</ref>

===Agamogenesis===
Agamogenesis is any form of reproduction that does not involve any union of gametes. Examples are [[parthenogenesis]] and [[apomixis]].

====Parthenogenesis====
{{main|Parthenogenesis}}

Parthenogenesis is a form of [[agamogenesis]] in which an unfertilized egg develops into a new individual. It has been documented in over 2,000 species.<ref name="Britannica">{{Cite web|title=parthenogenesis {{!}} Definition, Types, & Facts|url=https://www.britannica.com/science/parthenogenesis|access-date=2020-12-03|website=Encyclopedia Britannica|language=en}}</ref> Parthenogenesis occurs in the wild in many [[invertebrate]]s (e.g. water fleas, [[rotifer]]s, aphids, [[stick insect]]s, some ants, bees and parasitic wasps) and [[vertebrate]]s (mostly reptiles, amphibians, and fish). It has also been documented in domestic birds and in genetically altered lab mice.<ref>{{cite journal |last1=Kono |first1=Tomohiro |last2=Obata |first2=Yayoi |last3=Wu |first3=Quiong |last4=Niwa |first4=Katsutoshi |last5=Ono |first5=Yukiko |last6=Yamamoto |first6=Yuji |last7=Park |first7=Eun Sung |last8=Seo |first8=Jeong-Sun |last9=Ogawa |first9=Hidehiko |title=Birth of parthenogenetic mice that can develop to adulthood |journal=Nature |date=April 2004 |volume=428 |issue=6985 |pages=860–864 |doi=10.1038/nature02402 |pmid=15103378 }}</ref><ref>{{cite journal |last1=Ramachandran |first1=R |last2=McDaniel |first2=C D |title=Parthenogenesis in birds: a review |journal=Reproduction |date=June 2018 |volume=155 |issue=6 |pages=R245–R257 |doi=10.1530/REP-17-0728 |pmid=29559496 |doi-access=free }}</ref> Plants can engage in parthenogenesis as well through a process called [[apomixis]]. However this process is considered by many to not be an independent reproduction method, but instead a breakdown of the mechanisms behind sexual reproduction.<ref>{{cite book |doi=10.1016/B978-0-12-381466-1.00016-X |chapter=Regulation of apomixis |title=Plant Biotechnology and Agriculture |date=2012 |last1=Ozias-Akins |first1=Peggy |author-link1=Peggy Ozias-Akins|last2=Conner |first2=Joann A. |pages=243–254 |isbn=978-0-12-381466-1 }}</ref> Parthenogenetic organisms can be split into two main categories: facultative and obligate.

===== Facultative parthenogenesis =====
[[File:Zebra_Shark.jpg|thumb|Zebra shark]]
In facultative parthenogenesis, females can reproduce both sexually and asexually.<ref name="Britannica"/> Because of the many advantages of sexual reproduction, most facultative parthenotes only reproduce asexually when forced to. This typically occurs in instances when finding a mate becomes difficult. For example, female [[zebra shark]]s will reproduce asexually if they are unable to find a mate in their ocean habitats.<ref name="Dudgeon-2017"/>

Parthenogenesis was previously believed to rarely occur in vertebrates, and only be possible in very small animals. However, it has been discovered in many more species in recent years. Today, the largest species that has been documented reproducing parthenogenically is the [[Komodo dragon]] at 10 feet long and over 300 pounds.<ref>{{Cite web|last=Yam|first=Philip|title=Strange but True: Komodo Dragons Show that "Virgin Births" Are Possible|url=https://www.scientificamerican.com/article/strange-but-true-komodo-d/|access-date=2020-12-13|website=Scientific American|language=en}}</ref><ref>{{Cite web|date=2010-09-10|title=Komodo dragon|url=https://www.nationalgeographic.com/animals/reptiles/k/komodo-dragon/|archive-url=https://web.archive.org/web/20161017001707/http://www.nationalgeographic.com/animals/reptiles/k/komodo-dragon/|url-status=dead|archive-date=17 October 2016|access-date=2020-12-13|website=Animals|language=en}}</ref>
[[File:Aphid-giving-birth.jpg|thumb|[[Aphid]] giving birth to live young from an unfertilized egg]]
Heterogony is a form of facultative parthenogenesis where females alternate between sexual and asexual reproduction at regular intervals (see [[#Alternation between sexual and asexual reproduction|Alternation between sexual and asexual reproduction]]). [[Aphid]]s are one group of organism that engages in this type of reproduction. They use asexual reproduction to reproduce quickly and create winged offspring that can colonize new plants and reproduce sexually in the fall to lay eggs for the next season.<ref name="Stern-2008">{{cite journal |last1=Stern |first1=David L. |title=Aphids |journal=Current Biology |date=June 2008 |volume=18 |issue=12 |pages=R504–R505 |doi=10.1016/j.cub.2008.03.034 |pmid=18579086 |pmc=2974440 }}</ref> However, some aphid species are obligate parthenotes.<ref>{{cite journal |last1=Dedryver |first1=C-A |last2=Le Gallic |first2=J-F |last3=Mahéo |first3=F |last4=Simon |first4=J-C |last5=Dedryver |first5=F |title=The genetics of obligate parthenogenesis in an aphid species and its consequences for the maintenance of alternative reproductive modes |journal=Heredity |date=January 2013 |volume=110 |issue=1 |pages=39–45 |doi=10.1038/hdy.2012.57 |pmid=22990313 |pmc=3522239 }}</ref>

===== Obligate parthenogenesis =====
[[File:DesertGrasslandWhiptailLizard_AspidoscelisUniparens56.jpg|thumb|Desert grassland whiptail lizard females reproduce by obligate parthenogenesis.]]
In obligate parthenogenesis, females only reproduce asexually.<ref name="Britannica"/> One example of this is the [[desert grassland whiptail lizard]], a [[Hybrid (biology)|hybrid]] of two other species. Typically hybrids are infertile but through parthenogenesis this species has been able to develop stable populations.<ref>{{cite journal |last1=Crews |first1=David |last2=Fitzgerald |first2=Kevin T. |title='Sexual' behavior in parthenogenetic lizards (''Cnemidophorus'') |journal=Proceedings of the National Academy of Sciences |date=January 1980 |volume=77 |issue=1 |pages=499–502 |doi=10.1073/pnas.77.1.499 |doi-access=free |pmid=16592761 |pmc=348299 }}</ref>

[[Gynogenesis]] is a form of obligate parthenogenesis where a sperm cell is used to initiate reproduction. However, the sperm's genes never get incorporated into the egg cell. The best known example of this is the [[Amazon molly]]. Because they are obligate parthenotes, there are no males in their species so they depend on males from a closely related species (the [[Sailfin molly]]) for sperm.<ref>{{cite journal |last1=Tobler |first1=Michael |last2=Schlupp |first2=Ingo |title=Parasites in sexual and asexual mollies (''Poecilia'', Poeciliidae, Teleostei): a case for the Red Queen? |journal=Biology Letters |date=22 June 2005 |volume=1 |issue=2 |pages=166–168 |doi=10.1098/rsbl.2005.0305 |pmid=17148156 |pmc=1626213 }}</ref>

====Apomixis and nucellar embryony====
{{main|Apomixis |Nucellar embryony}}
Apomixis in plants is the formation of a new [[sporophyte]] without fertilization. It is important in ferns and in flowering plants, but is very rare in other seed plants. In flowering plants, the term "apomixis" is now most often used for [[agamospermy]], the formation of seeds without fertilization, but was once used to include [[vegetative reproduction]]. An example of an [[apomictic]] plant would be the [[triploid]] European [[dandelion]]. Apomixis mainly occurs in two forms: In gametophytic apomixis, the embryo arises from an unfertilized egg within a diploid embryo sac that was formed without completing meiosis. In [[nucellar embryony]], the embryo is formed from the diploid [[nucellus]] tissue surrounding the embryo sac. Nucellar embryony occurs in some [[citrus]] seeds. Male apomixis can occur in rare cases, such as in the Saharan Cypress ''[[Cupressus dupreziana]]'', where the genetic material of the embryo is derived entirely from [[pollen]].<ref>{{Cite web |title=Apomixis {{!}} reproduction {{!}} Britannica |url=https://www.britannica.com/science/apomixis |access-date=2023-03-23 |website=www.britannica.com |language=en}}</ref><ref>{{cite journal |last1=Zhang |first1=Siqi |last2=Liang |first2=Mei |last3=Wang |first3=Nan |last4=Xu |first4=Qiang |last5=Deng |first5=Xiuxin |last6=Chai |first6=Lijun |title=Reproduction in woody perennial Citrus: an update on nucellar embryony and self-incompatibility |journal=Plant Reproduction |date=March 2018 |volume=31 |issue=1 |pages=43–57 |doi=10.1007/s00497-018-0327-4 }}</ref><ref>{{Cite book |last1=Lotsy |first1=Johannes Paulus |url=https://www.biodiversitylibrary.org/item/46760 |title=Progressus rei botanicae = Fortschritte der Botanik = Progrès de la botanique = Progress of botany |last2=botanistes |first2=Association internationale des |date=1907 |publisher=G. Fischer |volume=2 |location=Jena}}</ref>

===Androgenesis===
{{main|Androgenesis}}
'''Androgenesis''' occurs when a [[zygote]] is produced with only paternal [[nuclear gene]]s. During standard [[sexual reproduction]], one female and one male parent each produce haploid [[gamete]]s (such as a sperm or egg cell, each containing only a single set of [[chromosome]]s), which recombine to create offspring with genetic material from both parents. However, in androgenesis, there is no recombination of maternal and paternal chromosomes, and only the paternal chromosomes are passed down to the offspring (the inverse of this is [[gynogenesis]], where only the maternal chromosomes are inherited, which is more common than androgenesis).<ref>{{cite journal |last1=Pigneur |first1=L-M |last2=Hedtke |first2=S M |last3=Etoundi |first3=E |last4=Van Doninck |first4=K |title=Androgenesis: a review through the study of the selfish shellfish Corbicula spp. |journal=Heredity |date=June 2012 |volume=108 |issue=6 |pages=581–591 |doi=10.1038/hdy.2012.3 |pmid=22473310 |pmc=3356815 }}</ref> The offspring produced in androgenesis will still have maternally inherited [[mitochondrion|mitochondria]], as is the case with most sexually reproducing species.
Androgenesis occurs in nature in many invertebrates (for example, clams,<ref name="Hedtke-2008"/> stick insects,<ref name="Tinti-1992">{{cite journal |last1=Tinti |first1=Fausto |last2=Scali |first2=Valerio |title=Genome exclusion and gametic dapi—dna content in the hybridogenetic Bacillus rossius—grandii benazzii complex (insecta phasmatodea) |journal=Molecular Reproduction and Development |date=November 1992 |volume=33 |issue=3 |pages=235–242 |doi=10.1002/mrd.1080330302 |pmid=1449790 }}</ref> some ants,<ref name="Fournier-2005">{{cite journal |last1=Fournier |first1=Denis |last2=Estoup |first2=Arnaud |last3=Orivel |first3=Jérôme |last4=Foucaud |first4=Julien |last5=Jourdan |first5=Hervé |last6=Breton |first6=Julien Le |last7=Keller |first7=Laurent |title=Clonal reproduction by males and females in the little fire ant |journal=Nature |date=June 2005 |volume=435 |issue=7046 |pages=1230–1234 |doi=10.1038/nature03705 |pmid=15988525 }}</ref> bees,<ref name="Schwander-2008" /> flies<ref name="Komma-1995">{{cite journal |last1=Komma |first1=D J |last2=Endow |first2=S A |title=Haploidy and androgenesis in Drosophila. |journal=Proceedings of the National Academy of Sciences |date=5 December 1995 |volume=92 |issue=25 |pages=11884–11888 |doi=10.1073/pnas.92.25.11884 |doi-access=free |pmid=8524868 |pmc=40507 }}</ref> and parasitic wasps<ref name="Schwander-2008" />) and vertebrates (mainly amphibians<ref name="Doležálková-Kaštánková-2024">{{cite web|url=https://link.springer.com/article/10.1186/s13293-018-0172-z|date=28 Sep 2024|title=All-male hybrids of a tetrapod Pelophylax esculentus share its origin and genetics of maintenance
}}</ref> and fish<ref name="Schwander-2008" /><ref name="Matos-2010">{{cite journal |last1=Matos |first1=I. |last2=Machado |first2=M.P. |last3=Sucena |first3=é. |last4=Collares-Pereira |first4=M.J. |last5=Schartl |first5=M. |last6=Coelho |first6=M.M. |title=Evidence for Hermaphroditism in the Squalius alburnoides Allopolyploid Fish Complex |journal=Sexual Development |date=2010 |volume=4 |issue=3 |pages=170–175 |doi=10.1159/000313359 }}</ref>). The [[androgenesis]] has also been seen in genetically modified laboratory mice.<ref>{{cite journal|language=en|title=Making mice with two dads: this biologist rewrote the rules on sexual reproduction|first=Heidi|last=Ledford|journal=Nature |date=2023 |volume=624 |issue=7992 |page=499 |doi=10.1038/d41586-023-03922-6 |pmid=38093054 |bibcode=2023Natur.624..499L |url=https://www.nature.com/articles/d41586-023-03922-6}}</ref>

One of two things can occur to produce offspring with exclusively paternal genetic material: the maternal nuclear genome can be eliminated from the zygote, or the female can produce an egg with no [[cell nucleus|nucleus]], resulting in an embryo developing with only the genome of the male gamete.

===Male apomixis===
Other type of androgenesis is the male apomixis or paternal apomixis is a reproductive process in which a plant develops from a sperm cell (male gamete) without the participation of a female cell (ovum). In this process, the zygote is formed solely with genetic material from the father, resulting in offspring genetically identical to the male organism.<ref name="Pichot-2008">{{cite journal |author1=Christian Pichot |author2=Benjamin Liens |author3=Juana L. Rivera Nava |author4=Julien B. Bachelier |author5=Mohamed El Maâtaoui |date=January 2008 |title=Cypress Surrogate Mother Produces Haploid Progeny From Alien Pollen |journal=Genetics|volume=178 |issue=1 |pages=379–383 |doi=10.1534/genetics.107.080572 |pmid=18202380 |pmc=2206086}}</ref><ref>{{cite journal|author1=Christian Pichot|author2=Bruno Fady|author3=Isabelle Hochu|year=2000|title=Lack of mother tree alleles in zymograms of ''Cupressus dupreziana'' A. Camus embryos|journal=Annals of Forest Science|volume=57|issue=1 |pages=17–22|doi=10.1051/forest:2000108|bibcode=2000AnFSc..57...17P |doi-access=free}}</ref><ref>{{cite journal|author1=Pichot, C. |author2=El Maataoui, M. |author3=Raddi, S. |author4=Raddi, P. |year=2001|title=Conservation: Surrogate mother for endangered ''Cupressus'' |journal=Nature |volume=412|issue=6842 |pages=39|doi=10.1038/35083687 |pmid=11452293 |s2cid=39046191 |doi-access=free}}</ref> This has been noted in many plants like ''[[Nicotiana]]'', ''[[Capsicum frutescens]]'', ''[[Cicer arietinum]]'', ''[[Poa arachnifera]]'', ''[[Solanum verrucosum]]'', ''[[Phaeophyceae]]'',<ref name="Heesch-2021">{{cite journal|first1=Svenja |last1=Heesch |first2=Martha |last2=Serrano-Serrano |first3=Josué |last3=Barrera-Redondo |first4=Rémy |last4=Luthringer |first5=Akira F |last5=Peters |first6=Christophe |last6=Destombe |first7=J Mark |last7=Cock |first8=Myriam |last8=Valero |first9=Denis |last9=Roze |first10=Nicolas |last10=Salamin |first11=Susana M |last11=Coelho |doi=10.1111/jeb.13880|title=Evolution of life cycles and reproductive traits: Insights from the brown algae |journal=Journal of Evolutionary Biology |volume=34 |issue=7 |date=July 2021 |url=https://onlinelibrary.wiley.com/doi/10.1111/jeb.13880?msockid=074e98058c4c6af62bbc8cee8d7d6b8c |pages=992-1009}} </ref> ''[[Pripsacum dactyloides]]'', ''[[Zea mays]]'',<ref name="Schwander-2008">{{cite web|first1=Tanja |last1=Schwander |first2=Benjamin P |last2=Oldroyd |url=https://royalsocietypublishing.org/doi/10.1098/rstb.2015.0534 |date=28 Sep 2008|title=Androgenesis: where males hijack eggs to clone themselves}}</ref> and occurs as the regular reproductive method in ''[[Cupressus dupreziana]]''.<ref name="Pichot-2008"/> This contrasts with the more common apomixis, where development occurs without fertilization, but with genetic material only from the mother.

There are also clonal species that reproduce through [[vegetative reproduction]] like ''[[Lomatia tasmanica]]''<ref name="Lynch-1998"/><ref name="Botanical Electronic News-1996"/> and [[Pando (tree)|''Pando'']],<ref name="DeWoody-2008">{{cite journal|last1=DeWoody |first1=Jennifer |last2=Rowe |first2= Carol A. |last3=Hipkins |first3= Valerie D. |last4=Mock |first4= Karen E. |date=2008 |title= "Pando" Lives: Molecular Genetic Evidence of a Giant Aspen Clone in Central Utah |journal=Western North American Naturalist |volume=68 |issue=4 |pages=493–497 |doi=10.3398/1527-0904-68.4.493|s2cid=59135424 |url=https://scholarsarchive.byu.edu/wnan/vol68/iss4/8}}</ref> where the genetic material is exclusively male.

Other species where [[androgenesis]] has been observed naturally are the stick insects ''[[Bacillus rossius]] and [[Bacillus (insect)|Bassillus Grandii]]'',<ref name="Tinti-1992"/> the little fire ant ''[[Wasmannia auropunctata]]'',<ref name="Fournier-2005"/> ''[[Vollenhovia emeryi]]'',<ref name="Schwander-2008" /> ''[[Paratrechina longicornis]]'',<ref name="Schwander-2008" /> occasionally in ''[[Apis mellifera]]'',<ref name="Schwander-2008" /> the ''[[Hypseleotris]]'' carp gudgeons,<ref name="Schwander-2008" /> the parasitoid ''[[Venturia (wasp)|Venturia canescens]]'',<ref name="Schwander-2008" /> and occasionally in fruit flies ''[[Drosophila melanogaster]]'' carrying a specific mutant allele.<ref name="Komma-1995"/> It has also been induced in many crops and fish via irradiation of an egg cell to destroy the maternal nuclear genome.<ref name="Basavaraju-2023">{{cite book |doi=10.1016/B978-0-323-91240-2.00012-9 |chapter=Monosex population in aquaculture |title=Frontiers in Aquaculture Biotechnology |date=2023 |last1=Basavaraju |first1=Yaraguntappa |pages=89–101 |isbn=978-0-323-91240-2 }}</ref>

==== Obligate androgenesis ====

Obligate androgenesis is the process in which males<ref name="Hedtke-2008">{{cite journal |last1=Hedtke |first1=Shannon M. |last2=Stanger-Hall |first2=Kathrin |last3=Baker |first3=Robert J. |last4=Hillis |first4=David M. |title=All-Male Asexuality: Origin and Maintenance of Androgenesis in the Asian Clam Corbicula |journal=Evolution |date=May 2008 |volume=62 |issue=5 |pages=1119–1136 |doi=10.1111/j.1558-5646.2008.00344.x |pmid=18266987 }}</ref> are capable of producing both eggs and sperm, however, the eggs have no genetic contribution and the offspring come only from the sperm, which allows these individuals to self-fertilize and produce clonal offspring without the need for females. They are also capable of interbreeding with sexual and other androgenetic lineages in a phenomenon known as "egg parasitism." This method of reproduction has been found in several species of the clam genus ''[[Corbicula]]'',<ref name="Hedtke-2008"/> many plants like, ''[[Cupressus dupreziana]]'',<ref name="Pichot-2001">{{Cite journal |last=Pichot |first=C. |last2=El Maâtaoui |first2=M. |last3=Raddi |first3=S. |last4=Raddi |first4=P. |date=2001-07-05 |title=Surrogate mother for endangered Cupressus |url=https://pubmed.ncbi.nlm.nih.gov/11452293/ |journal=Nature |volume=412 |issue=6842 |pages=39 |doi=10.1038/35083687 |issn=0028-0836 |pmid=11452293}}</ref> ''[[Lomatia tasmanica]]'',<ref name="Lynch-1998"/><ref name="Botanical Electronic News-1996"/> ''[[Pando (tree)|Pando]]''<ref name="DeWoody-2008">{{cite journal|last1=DeWoody |first1=Jennifer |last2=Rowe |first2= Carol A. |last3=Hipkins |first3= Valerie D. |last4=Mock |first4= Karen E. |date=2008 |title= "Pando" Lives: Molecular Genetic Evidence of a Giant Aspen Clone in Central Utah |journal=Western North American Naturalist |volume=68 |issue=4 |pages=493–497 |doi=10.3398/1527-0904-68.4.493|s2cid=59135424 |url=https://scholarsarchive.byu.edu/wnan/vol68/iss4/8}}</ref> and recently in the fish ''[[Squalius alburnoides]]''.<ref name="Matos-2010"/> 

Other species where [[androgenesis]] has been observed naturally are the stick insects ''[[Bacillus rossius]] and [[Bacillus (insect)|Bassillus Grandii]]'',<ref name="Tinti-1992"/> the little fire ant ''[[Wasmannia auropunctata]]'',<ref name="Fournier-2005"/> ''[[Vollenhovia emeryi]]'',<ref name="Schwander-2008" /> ''[[Paratrechina longicornis]]'',<ref name="Schwander-2008" /> occasionally in ''[[Apis mellifera]]'',<ref name="Schwander-2008" /> the ''[[Hypseleotris]]'' carp gudgeons,<ref name="Schwander-2008" /> the parasitoid ''[[Venturia (wasp)|Venturia canescens]]'',<ref name="Schwander-2008" /> and occasionally in fruit flies ''[[Drosophila melanogaster]]'' carrying a specific mutant allele.<ref name="Komma-1995"/> It has also been induced in many crops and fish via irradiation of an egg cell to destroy the maternal nuclear genome.<ref name="Basavaraju-2023"/>

==Alternation between sexual and asexual reproduction==
{{See also |Plant reproduction#Sexual reproduction}}
[[File:Soybeanaphidlifecycle.gif|thumb|upright=1.7|[[Aphid]] populations are often entirely female during the summer, with sexual reproduction only to produce eggs for overwintering.]]Some species can alternate between sexual and asexual strategies, an ability known as ''[[heterogamy]]'', depending on many conditions. Alternation is observed in several [[rotifer]] species (cyclical parthenogenesis e.g. in [[Brachionus]] species) and a few types of insects.

One example of this is [[aphid]]s which can engage in heterogony. In this system, females are born pregnant and produce only female offspring. This cycle allows them to reproduce very quickly. However, most species reproduce sexually once a year. This switch is triggered by environmental changes in the fall and causes females to develop eggs instead of embryos. This dynamic reproductive cycle allows them to produce specialized offspring with [[polyphenism]], a type of [[Polymorphism (biology)|polymorphism]] where different phenotypes have evolved to carry out specific tasks.<ref name="Stern-2008"/>

The cape bee [[Apis mellifera capensis|''Apis mellifera'' subsp. ''capensis'']] can reproduce asexually through a process called [[thelytoky]]. The freshwater crustacean ''[[Daphnia]]'' reproduces by parthenogenesis in the spring to rapidly populate ponds, then switches to [[sexual reproduction]] as the intensity of competition and predation increases. Monogonont [[rotifer]]s of the genus ''[[Brachionus]]'' reproduce via cyclical parthenogenesis: at low population densities females produce asexually and at higher densities a chemical cue accumulates and induces the transition to sexual reproduction. Many protists and fungi alternate between sexual and asexual reproduction. A few species of amphibians, reptiles, and birds have a similar ability.{{which|date=November 2021}}

{{which|date=February 2020}}

The slime mold ''[[Dictyostelium]]'' undergoes binary fission (mitosis) as single-celled amoebae under favorable conditions. However, when conditions turn unfavorable, the cells aggregate and follow one of two different developmental pathways, depending on conditions. In the social pathway, they form a multi-cellular slug which then forms a fruiting body with asexually generated spores. In the sexual pathway, two cells fuse to form a giant cell that develops into a large cyst. When this macrocyst germinates, it releases hundreds of amoebic cells that are the product of meiotic recombination between the original two cells.<ref name="Mehotra-1990">{{cite book |author1=Mehrotra, R. S. |author2=Aneja, K. R. |title=An Introduction to Mycology |url=https://books.google.com/books?id=UUorj_O2dcsC&pg=PA83|date=December 1990|publisher=New Age International |isbn=978-81-224-0089-2 |pages=83 ff}}</ref>

The hyphae of the common mold (''[[Rhizopus]]'') are capable of producing both mitotic as well as meiotic spores. Many algae similarly switch between sexual and asexual reproduction.<ref name="Cole-1990">{{cite book |author1=Cole, Kathleen M. |author2=Sheath, Robert G. |title=Biology of the red algae |url=https://books.google.com/books?id=F7CWXuYZFq8C&pg=PA469|year=1990|publisher=Cambridge University Press |isbn=978-0-521-34301-5 |page=469}}</ref> A number of plants use both sexual and asexual means to produce new plants, some species alter their primary modes of reproduction from sexual to asexual under varying environmental conditions.<ref name="Reekie-2005">{{cite book |author1=Edward G. Reekie |author2-link=Fakhri A. Bazzaz |author2=Fakhri A. Bazzaz |title=Reproductive allocation in plants |url=https://books.google.com/books?id=_KJdaiLKAogC&pg=PA99|year=2005|publisher=Academic Press |isbn=978-0-12-088386-8 |page=99}}</ref>

==Inheritance in asexual species==
In the [[rotifer]] ''[[Brachionus]] calyciflorus'' asexual reproduction (obligate [[parthenogenesis]]) can be inherited by a recessive allele, which leads to loss of sexual reproduction in homozygous offspring.<ref>{{cite journal | last1=Stelzer | first1=C.-P. | last2=Schmidt | first2=J. | last3=Wiedlroither | first3=A. | last4=Riss | first4=S. | year=2010 | title=Loss of Sexual Reproduction and Dwarfing in a Small Metazoan | journal=PLOS ONE | volume=5 | issue=9 | page=e12854 | doi=10.1371/journal.pone.0012854 | pmid=20862222 | pmc=2942836| bibcode=2010PLoSO...512854S | doi-access=free }}</ref><ref>{{cite journal | last1=Scheuerl | first1=T. | last2=Riss | first2=S. | last3=Stelzer | first3=C.P. | year=2011 | title=Phenotypic effects of an allele causing obligate parthenogenesis in a rotifer | journal=Journal of Heredity | volume=102 | issue=4 | pages=409–415 | doi=10.1093/jhered/esr036 | pmid=21576287 | pmc=3113615}}</ref><br />
Inheritance of asexual reproduction by a single recessive locus has also been found in the [[parasitoid wasp]] ''Lysiphlebus fabarum''.<ref>{{cite journal |last1=Sandrock |first1=Christoph |last2=Vorburger |first2=Christoph |title=Single-Locus Recessive Inheritance of Asexual Reproduction in a Parasitoid Wasp |journal=Current Biology |date=March 2011 |volume=21 |issue=5 |pages=433–437 |doi=10.1016/j.cub.2011.01.070 |url=https://www.dora.lib4ri.ch/eawag/islandora/object/eawag%3A6665 }}</ref>

==Examples in animals==

Asexual reproduction is found in nearly half of the animal phyla.<ref>{{cite book |last1=Minelli |first1=Alessandro |title=Perspectives in Animal Phylogeny and Evolution |date=2009 |publisher=Oxford University Press |isbn=978-0-19-856620-5 |pages=123–127 }}</ref> Parthenogenesis occurs in the [[hammerhead shark]]<ref>{{cite news |last=Savage |first=Juliet Eilperin |title=Female Sharks Can Reproduce Alone, Researchers Find |newspaper=The Washington Post|date= 23 May 2007 |url=https://www.washingtonpost.com/wp-dyn/content/article/2007/05/22/AR2007052201405.html }}</ref> and the [[blacktip shark]].<ref>{{cite press release |title='Virgin Birth' By Shark Confirmed: Second Case Ever |url=https://www.sciencedaily.com/releases/2008/10/081010173054.htm |work=ScienceDaily |publisher=Stony Brook University |date=11 October 2008 }}</ref><ref>{{cite journal |last1=Chapman |first1=D. D. |last2=Firchau |first2=B. |last3=Shivji |first3=M. S. |title=Parthenogenesis in a large-bodied requiem shark, the blacktip Carcharhinus limbatus |journal=Journal of Fish Biology |date=October 2008 |volume=73 |issue=6 |pages=1473–1477 |doi=10.1111/j.1095-8649.2008.02018.x }}</ref> In both cases, the sharks had reached sexual maturity in captivity in the absence of males, and in both cases the offspring were shown to be genetically identical to the mothers. The [[New Mexico whiptail]] is another example.

Some reptiles use the [[ZW sex-determination system]], which produces either males (with ZZ sex chromosomes) or females (with ZW or WW sex chromosomes). Until 2010, it was thought that the ZW chromosome system used by reptiles was incapable of producing viable WW offspring, but a (ZW) female [[boa constrictor]] was discovered to have produced viable female offspring with WW chromosomes.<ref>{{cite web |url=http://www.cbc.ca/news/technology/boa-constrictor-produces-fatherless-babies-1.947269 |title=Boa constrictor produces fatherless babies |publisher=CBC News – Technology & Science |date=3 November 2010 |access-date=2014-10-20}}</ref> The female boa could have chosen any number of male partners (and had successfully in the past) but on this occasion she reproduced asexually, creating 22 female babies with WW sex-chromosomes.

[[Polyembryony]] is a widespread form of asexual reproduction in animals, whereby the fertilized egg or a later stage of embryonic development splits to form genetically identical clones. Within animals, this phenomenon has been best studied in the parasitic [[Hymenoptera]]. In the [[nine-banded armadillos]], this process is obligatory and usually gives rise to genetically identical quadruplets. In other mammals, [[monozygotic twinning]] has no apparent genetic basis, though its occurrence is common. There are at least 10 million identical human twins and triplets in the world today.

Bdelloid [[rotifer]]s reproduce exclusively asexually, and all individuals in the class [[Bdelloidea]] are females. Asexuality evolved in these animals millions of years ago and has persisted since. There is evidence to suggest that asexual reproduction has allowed the animals to evolve new proteins through the [[Matthew Meselson#Meselson effect|Meselson effect]] that have allowed them to survive better in periods of dehydration.<ref>{{cite journal |last1=Pouchkina-Stantcheva |first1=N. N. |last2=McGee |first2=B. M. |last3=Boschetti |first3=C. |last4=Tolleter |first4=D. |last5=Chakrabortee |first5=S. |last6=Popova |first6=A. V. |last7=Meersman |first7=F. |last8=MacHerel |first8=D. |last9=Hincha |first9=D. K. |title=Functional Divergence of Former Alleles in an Ancient Asexual Invertebrate |journal=Science |volume=318 |issue=5848 |pages=268–71 |year=2007 |pmid=17932297 |doi=10.1126/science.1144363|bibcode=2007Sci...318..268P |doi-access=free }}</ref> Bdelloid rotifers are extraordinarily resistant to damage from [[ionizing radiation]] due to the same DNA-preserving adaptations used to survive dormancy.<ref name="Gladyshev-2008">{{cite journal |last1=Gladyshev |first1=Eugene |last2=Meselson |first2=Matthew |title=Extreme resistance of bdelloid rotifers to ionizing radiation |journal=Proceedings of the National Academy of Sciences |date=April 2008 |volume=105 |issue=13 |pages=5139–5144 |doi=10.1073/pnas.0800966105 |pmid=18362355 |pmc=2278216 |bibcode=2008PNAS..105.5139G |doi-access=free }}</ref> These adaptations include an extremely efficient mechanism for repairing DNA double-strand breaks.<ref name="Hespeels-2014">{{cite journal |last1=Hespeels |first1=B. |last2=Knapen |first2=M. |last3=Hanot-Mambres |first3=D. |last4=Heuskin |first4=A.-C. |last5=Pineux |first5=F. |last6=Lucas |first6=S. |last7=Koszul |first7=R. |last8=van Doninck |first8=K. |title=Gateway to genetic exchange? DNA double-strand breaks in the bdelloid rotifer A dineta vaga submitted to desiccation |journal=Journal of Evolutionary Biology |date=July 2014 |volume=27 |issue=7 |pages=1334–1345 |doi=10.1111/jeb.12326 |pmid=25105197 |url=https://hal-pasteur.archives-ouvertes.fr/pasteur-01420001/file/hespeels%20et%20al%202014.pdf }}</ref> This repair mechanism was studied in two Bdelloidea species, ''Adineta vaga'',<ref name="Hespeels-2014" /> and ''Philodina roseola''.<ref name="Welch-2008">{{cite journal |author=Welch, David B. Mark |author2=Welch, Jessica L. Mark |author3=Meselson, Matthew |name-list-style=amp|title=Evidence for degenerate tetraploidy in bdelloid rotifers |journal=Proceedings of the National Academy of Sciences |volume=105 |issue=13 |pages=5145–9 |date=April 2008 |pmid=18362354 |pmc=2278229 |doi=10.1073/pnas.0800972105 |bibcode=2008PNAS..105.5145M |doi-access=free }}</ref> and appears to involve mitotic recombination between homologous DNA regions within each species.

Molecular evidence strongly suggests that several species of the [[stick insect]] genus ''[[Timema]]'' have used only asexual (parthenogenetic) reproduction for millions of years, the longest period known for any insect.<ref>{{cite journal |last1=Schwander |first1=Tanja |last2=Henry |first2=Lee |last3=Crespi |first3=Bernard J. |title=Molecular Evidence for Ancient Asexuality in Timema Stick Insects |journal=Current Biology |date=July 2011 |volume=21 |issue=13 |pages=1129–1134 |doi=10.1016/j.cub.2011.05.026 |pmid=21683598 }}</ref> Similar findings suggest that the [[mite]] species ''[[Oppiella nova]]'' may have reproduced entirely asexually for millions of years.<ref>{{cite journal |last1=Brandt |first1=Alexander |last2=Tran Van |first2=Patrick |last3=Bluhm |first3=Christian |last4=Anselmetti |first4=Yoann |last5=Dumas |first5=Zoé |last6=Figuet |first6=Emeric |last7=François |first7=Clémentine M. |last8=Galtier |first8=Nicolas |last9=Heimburger |first9=Bastian |last10=Jaron |first10=Kamil S. |last11=Labédan |first11=Marjorie |last12=Maraun |first12=Mark |last13=Parker |first13=Darren J. |last14=Robinson-Rechavi |first14=Marc |last15=Schaefer |first15=Ina |last16=Simion |first16=Paul |last17=Scheu |first17=Stefan |last18=Schwander |first18=Tanja |last19=Bast |first19=Jens |title=Haplotype divergence supports long-term asexuality in the oribatid mite Oppiella nova |journal=Proceedings of the National Academy of Sciences |date=21 September 2021 |volume=118 |issue=38 |doi=10.1073/pnas.2101485118 |doi-access=free |pmid=34535550 |hdl=20.500.11820/9db5ad45-0faf-4260-a6e2-c6d4406874ba |hdl-access=free }}</ref>

In the grass [[thrips]] genus ''[[Aptinothrips]]'' there have been several transitions to asexuality, likely due to different causes.<ref>{{cite journal |first1=C. J. |last1=van der Kooi |first2=T. |last2=Schwander |year=2014 |title=Evolution of asexuality via different mechanisms in grass thrips (Thysanoptera: ''Aptinothrips'') |journal=[[Evolution (journal)|Evolution]] |volume=86 |issue=7 |pages=1883–1893 |doi=10.1111/evo.12402 |pmid=24627993 |s2cid=14853526 }}</ref>

== Adaptive significance of asexual reproduction ==
A complete lack of [[sexual reproduction]] is relatively rare among [[multicellular organism]]s, particularly [[animal]]s. It is not entirely understood why the ability to reproduce sexually is so common among them. Current hypotheses<ref name="Dawson-1995">{{cite journal |author=Dawson, K.J. |title=The Advantage of Asexual Reproduction: When is it Two-fold? |journal=Journal of Theoretical Biology |date=October 1995 |volume=176 |pages=341–347 |issue=3 |doi=10.1006/jtbi.1995.0203|bibcode=1995JThBi.176..341D }}</ref> suggest that asexual reproduction may have short term benefits when rapid population growth is important or in stable environments, while sexual reproduction offers a net advantage by allowing more rapid generation of genetic diversity, allowing adaptation to changing environments. Developmental constraints<ref name="Engelstädter-2008">{{cite journal |author=Engelstädter, J. |title=Constraints on the evolution of asexual reproduction |journal=BioEssays |date=November 2008 |volume=30 |pages=1138–1150 |issue=11–12 |pmid=18937362 |doi=10.1002/bies.20833|s2cid=5357709 }}</ref> may underlie why few animals have relinquished sexual reproduction completely in their life-cycles. Almost all asexual modes of reproduction maintain meiosis either in a modified form or as an alternative pathway.<ref name="Hörandl-2013">{{Cite journal |doi=10.1007/s00497-013-0234-7 |doi-access=free |pmc=3825497 |pmid=23995700|title=The oxidative damage initiation hypothesis for meiosis |year=2013 |last1=Hörandl |first1=Elvira |last2=Hadacek |first2=Franz |journal=Plant Reproduction |volume=26 |issue=4 |pages=351–367 }}</ref> Facultatively apomictic plants increase frequencies of sexuality relative to apomixis after abiotic stress.<ref name="Hörandl-2013"/> Another constraint on switching from sexual to asexual reproduction would be the concomitant loss of meiosis and the protective recombinational repair of DNA damage afforded as one function of meiosis.<ref name="Michod-1987">{{cite book |author1=Bernstein, H. |author2=Hopf, F.A. |author3=Michod, R.E.  |chapter=The Molecular Basis of the Evolution of Sex |title=Molecular Genetics of Development |volume=24 |pages=323–70 |year=1987 |pmid=3324702 |doi= 10.1016/s0065-2660(08)60012-7 |series=Advances in Genetics |isbn=9780120176243 }}</ref><ref>Avise, J. (2008) Clonality: The Genetics, Ecology and Evolution of Sexual Abstinence in Vertebrate Animals. See pp. 22–25. Oxford University Press. {{ISBN |019536967X}} {{ISBN |978-0195369670}}</ref>

==See also==
{{Div col}}
* [[Alternation of generations]]
* [[Autogamy|Self-fertilization]]
* [[Bacterial conjugation]]
* [[Biological life cycle]]
* [[Biological reproduction]], also simply [[reproduction]]
* [[Cloning]]
* [[Hermaphrodite]]
* [[Plant reproduction]]
* [[Sex]]
{{colend}}

==References==
{{Reflist|refs=

<ref name="Botanical Electronic News-1996">
{{Cite web | title= The Oldest Living Plant Individual | date= 8 November 1996 | website= Botanical Electronic News | url= http://www.ou.edu/cas/botany-micro/ben/ben149.html | access-date= 11 November 2013 }}
</ref>

<ref name="Lynch-1998">
{{Cite journal | last1= Lynch | first1= A. J. J. | last2= Barnes | first2= R. W. | last3= Vaillancourt | first3= R. E. | last4= Cambecèdes | first4= J. | year= 1998 | title= Genetic evidence that ''Lomatia tasmanica'' (Proteaceae) is an ancient clone | journal= Australian Journal of Botany | volume= 46 | issue= 1 | pages= 25–33 | doi= 10.1071/BT96120 | url= http://eprints.utas.edu.au/7645/1/Lynch1998.pdf | access-date= 11 November 2013 }}
</ref>


}}

==Further reading==
* {{cite book |last=Avise |first=J. |year=2008 |title=Clonality: The Genetics, Ecology, and Evolution of Sexual Abstinence in Vertebrate Animals |publisher=Oxford University Press |isbn=978-0-19-536967-0 }}
* {{cite book |last1=Graham |first1=L. |last2=Graham |first2=J. |last3=Wilcox |first3=L. |year=2003 |title=Plant Biology |publisher=Pearson Education |location=Upper Saddle River, NJ |pages=258–259 |isbn=978-0-13-030371-4 }}
* {{cite book |last1=Raven |first1=P. H. |last2=Evert |first2=R. F. |last3=Eichhorn |first3=S. E. |year=2005 |title=Biology of Plants |url=https://archive.org/details/biologyofplants00rave_0 |url-access=registration |edition=7th |publisher=W.H. Freeman and Company |location=NY |isbn=978-0-7167-6284-3 }}

==External links==
{{Commons category |Asexual reproduction}}
* [https://web.archive.org/web/20050708073801/http://www.tiscali.co.uk/reference/encyclopaedia/hutchinson/m0030820.html Asexual reproduction]
* [http://www.tulane.edu/~wiser/protozoology/notes/intes.html Intestinal Protozoa]

{{Authority control}}

{{DEFAULTSORT:Asexual Reproduction}}
[[Category:Asexual reproduction| ]]