dioicy
{{Short description|Sexual system in non-vascular plants}}
{{Distinguish|Dioecy}}
Dioicy ({{IPAc-en|d|aɪ|ˈ|oʊ|ə|s|i}}) is a sexual system in non-vascular plants where archegonia (female organs) and antheridia (male organs) are produced on separate plants in the gametophyte phase.{{Cite journal|last1=Villarreal|first1=Juan Carlos|last2=Renner|first2=Susanne S.|author-link2=Susanne Renner|date=2013-11-02|title=Correlates of monoicy and dioicy in hornworts, the apparent sister group to vascular plants|journal=BMC Evolutionary Biology|language=en|volume=13|issue=1|pages=239|doi=10.1186/1471-2148-13-239|issn=1471-2148|pmc=4228369|pmid=24180692 |doi-access=free }} It is one of the two main sexual systems in bryophytes, the other being monoicy. Both dioicous ({{IPAc-en|d|aɪ|ˈ|oʊ|ə|k|ə|s}}) and monoicous gametophytes produce gametes in gametangia by mitosis rather than meiosis, so that sperm and eggs are genetically identical with their parent gametophyte.{{Cite book|last=Goffinet|first=Bernard|url=https://books.google.com/books?id=te0fAwAAQBAJ&q=dioicy|title=Bryophyte Biology|date=2008-10-30|publisher=Cambridge University Press|isbn=978-1-107-37728-8|language=en}}
== Description ==
Dioicy promotes outcrossing.{{Cite book|last=Windsor|first=Jon and Lesley Lovett-Doust Professor of Biology the University of|url=https://books.google.com/books?id=Yjv1woP0QtYC&q=dioicy+liverworts&pg=PA292|title=Plant Reproductive Ecology : Patterns and Strategies: Patterns and Strategies|date=1988-07-07|publisher=Oxford University Press, USA|isbn=978-0-19-802192-6|pages=291–292|language=en}} Sexual dimorphism is commonly found in dioicous species.{{rp|71}}{{rp|378}} Dioicy is correlated with reduced sporophyte production,{{Cite book|last=Windsor|first=Jon and Lesley Lovett-Doust Professor of Biology the University of|url=https://books.google.com/books?id=Yjv1woP0QtYC&q=dioicy+liverworts&pg=PA292|title=Plant Reproductive Ecology : Patterns and Strategies: Patterns and Strategies|date=1988-07-07|publisher=Oxford University Press, USA|isbn=978-0-19-802192-6|pages=295|language=en}} due to spatial separation of male and female colonies, scarcity or absence of males.{{Rp|location=65}}
The term dioecy is inapplicable to bryophytes because it refers to the sexuality of vascular plant sporophytes.{{Cite book |url=https://books.google.com/books?id=qXvSBQAAQBAJ&q=Sexual+systems+in+bryophytes&pg=PA62 |title=Reproductive Biology of Plants |vauthors=Ramawat KG, Merillon JM, Shivanna KR|date=2016-04-19 |publisher=CRC Press |isbn=978-1-4822-0133-8 |language=en }}{{rp|62}} Nonetheless dioecy and dioicy are comparable in many respects.{{Cite journal|last1=Bisang|first1=Irene|last2=Ehrlén|first2=Johan|last3=Hedenäs|first3=Lars|date=2006|title=Reproductive effort and costs of reproduction do not explain female-biased sex ratios in the moss Pseudocalliergon trifarium (Amblystegiaceae) |journal=American Journal of Botany|language=en |volume=93 |issue=9 |pages=1313–1319 |doi=10.3732/ajb.93.9.1313 |pmid=21642196|issn=1537-2197|doi-access=free}}
Etymology
The words dioicous and di(o)ecious are derived from οἶκος or οἰκία and δι- (di-), twice, double. ((o)e is the Latin way of transliterating Greek οι, whereas oi is a more straightforward modern way.) Generally, the term and "dioicous" have been restricted to description of haploid sexuality (gametophytic sexuality), and are thus primarily to describe bryophytes in which the gametophyte is the dominant generation. Meanwhile, "dioecious" is used to describe diploid sexuality (sporophytic sexuality), and thus is used to describe tracheophytes (vascular plants) in which the sporophyte is the dominant generation.{{cite book|author=Buck WR & Goffinet B|title=Bryophyte Biology|date=2000|publisher=Cambridge University Press|isbn=978-0-521-66794-4|editor=Shaw AJ & Goffinet B|location=New York|chapter=Morphology and classification of mosses}}{{rp|82}}
Occurrence
Sixty-eight percent of liverwort species, 57% to 60%{{Cite book|last=Rensing |first=Stefan |url=https://books.google.com/books?id=LlfBBwAAQBAJ&q=Dioicy&pg=PA109|chapter=Genomes and Evolution of Charophytes, Bryophytes, Lycophytes and Ferns|date=2016-03-23|title=Advances in Botanical Research |volume=78 |publisher=Academic Press|isbn=978-0-12-801324-3|pages=109|language=en}} of moss species, and 40% of hornwort species are dioicous. Dioicy also occurs in algae such as Charales and Coleochaetales.{{Rp|location=71}}It is also prevalent in brown algae.{{Cite journal|last1=Zhang|first1=Jiaxun|last2=Li|first2=Yan|last3=Luo|first3=Shiju|last4=Cao|first4=Min|last5=Zhang|first5=Linan|last6=Li|first6=Xiaojie|date=2021-07-14|title=Differential gene expression patterns during gametophyte development provide insights into sex differentiation in the dioicous kelp Saccharina japonica|journal=BMC Plant Biology|volume=21|issue=1|pages=335|doi=10.1186/s12870-021-03117-z|issn=1471-2229|pmc=8278619|pmid=34261451 |doi-access=free }}{{Clarification needed|date=October 2021}}
In all cases sex determination is genetic.{{Cite journal|last=Renner|first=Susanne S.|author-link=Susanne Renner|date=2014|title=The relative and absolute frequencies of angiosperm sexual systems: Dioecy, monoecy, gynodioecy, and an updated online database|journal=American Journal of Botany|language=en|volume=101|issue=10|pages=1588–1596|doi=10.3732/ajb.1400196|pmid=25326608|issn=1537-2197|doi-access=free}}
Evolution of dioicy
{{Main|Evolution of sexual reproduction}}
The ancestral sexual system in bryophytes is unknown but it has been suggested monoicy and dioicy evolved several times.{{Cite journal|last1=McDaniel|first1=Stuart F.|last2=Perroud|first2=Pierre-François|date=2012|title=Invited perspective: bryophytes as models for understanding the evolution of sexual systems|url=https://www.jstor.org/stable/41486736|journal=The Bryologist|volume=115|issue=1|pages=1–11|doi=10.1639/0007-2745-115.1.1|issn=0007-2745|jstor=41486736|s2cid=85943617|url-access=subscription}} It has also been suggested that dioicy is a plesiomorphic character for bryophytes.{{Rp|71}} In order for dioicy to evolve from monoicy it needs two mutations, a male sterility mutation and a female sterility mutation.
Hornworts have gone through twice as many transitions from dioicy to monoicy than monoicy to dioicy.
Among moss species the transition from monoicy to dioicy is more common than dioicy to monoicy{{Cite book|url=https://books.google.com/books?id=LlfBBwAAQBAJ&q=dioicy+evolved+in+liverworts&pg=PA109|title=Genomes and Evolution of Charophytes, Bryophytes, Lycophytes and Ferns|date=2016-03-23|publisher=Academic Press|isbn=978-0-12-801324-3|pages=109|language=en}} with there being at least 133 transitions from monoicy to dioicy in moss. Sexual specialization has been used as an explanation for this recurring evolution of dioicy in mosses.{{Rp|page=71}}