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Dioicy ( /dˈəsi/) is a sexual system where archegonia and antheridia are produced on separate gametophytes. [1] It is one of the two main sexual systems in bryophytes, the other being monoicy. Both dioicous ( /dˈəkəs/) and monoicous gametophytes produce gametes in gametangia by mitosis rather than meiosis, so that sperm and eggs are genetically identical with their parent gametophyte. [2]

Description

Dioicy promotes outcrossing. [3] Sexual dimorphism is commonly found in dioicous species. [4]: 71  [2]: 378  Dioicy is correlated with reduced sporophyte production, [5] due to spatial separation of male and female colonies, scarcity or absence of males. [4]: 65 

The term dioecy is inapplicable to bryophytes because it refers to the sexuality of vascular plant sporophytes. [4]: 62  Nonetheless dioecy and dioicy are comparable in many respects. [6]

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" are used to describe diploid sexuality ( sporophytic sexuality), and thus are used to describe tracheophytes (vascular plants) in which the sporophyte is the dominant generation. [7] [8]: 82 

Occurrence

68% of liverwort species, [1] 57% to 60% [9] of moss species, and 40% of hornwort species are dioicous. [1] Dioicy also occurs in algae such as Charales and Coleochaetales. [4]: 71 It is also prevalent in brown algae. [10][ clarification needed]

In all cases sex determination is genetic. [11]

Evolution of dioicy

The ancestral sexual system in bryophytes is unknown but it has been suggested monoicy and dioicy evolved several times. [12] It has also been suggested that dioicy is a plesiomorphic character for bryophytes. [4]: 71  In order for dioicy to evolve from monoicy it needs two mutations, a male sterility mutation and a female sterility mutation. [12]

Hornworts have gone through twice as many transitions from dioicy to monoicy than monoicy to dioicy. [1]

Among moss species the transition from monoicy to dioicy is more common than dioicy to monoicy [13] 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. [4]: 71 

References

  1. ^ a b c d Villarreal, Juan Carlos; Renner, Susanne S. (2013-11-02). "Correlates of monoicy and dioicy in hornworts, the apparent sister group to vascular plants". BMC Evolutionary Biology. 13 (1): 239. doi: 10.1186/1471-2148-13-239. ISSN  1471-2148. PMC  4228369. PMID  24180692.
  2. ^ a b Goffinet, Bernard (2008-10-30). Bryophyte Biology. Cambridge University Press. ISBN  978-1-107-37728-8.
  3. ^ Windsor, Jon and Lesley Lovett-Doust Professor of Biology the University of (1988-07-07). Plant Reproductive Ecology : Patterns and Strategies: Patterns and Strategies. Oxford University Press, USA. pp. 291–292. ISBN  978-0-19-802192-6.
  4. ^ a b c d e f Ramawat KG, Merillon JM, Shivanna KR (2016-04-19). Reproductive Biology of Plants. CRC Press. ISBN  978-1-4822-0133-8.
  5. ^ Windsor, Jon and Lesley Lovett-Doust Professor of Biology the University of (1988-07-07). Plant Reproductive Ecology : Patterns and Strategies: Patterns and Strategies. Oxford University Press, USA. p. 295. ISBN  978-0-19-802192-6.
  6. ^ Bisang, Irene; Ehrlén, Johan; Hedenäs, Lars (2006). "Reproductive effort and costs of reproduction do not explain female-biased sex ratios in the moss Pseudocalliergon trifarium (Amblystegiaceae)". American Journal of Botany. 93 (9): 1313–1319. doi: 10.3732/ajb.93.9.1313. ISSN  1537-2197. PMID  21642196.
  7. ^ Villarreal, J.C.; Renner, S.S. (2013). "Correlates of monoicy and dioicy in hornworts, the apparent sister group to vascular plants". BMC Evolutionary Biology. 13 (239): 1471–2148. doi: 10.1186/1471-2148-13-239. PMC  4228369. PMID  24180692.
  8. ^ Buck WR & Goffinet B (2000). "Morphology and classification of mosses". In Shaw AJ & Goffinet B (ed.). Bryophyte Biology. New York: Cambridge University Press. ISBN  978-0-521-66794-4.
  9. ^ Rensing, Stefan (2016-03-23). Advances in Botanical Research. Vol. 78. Academic Press. p. 109. ISBN  978-0-12-801324-3. {{ cite book}}: |work= ignored ( help)
  10. ^ Zhang, Jiaxun; Li, Yan; Luo, Shiju; Cao, Min; Zhang, Linan; Li, Xiaojie (2021-07-14). "Differential gene expression patterns during gametophyte development provide insights into sex differentiation in the dioicous kelp Saccharina japonica". BMC Plant Biology. 21 (1): 335. doi: 10.1186/s12870-021-03117-z. ISSN  1471-2229. PMC  8278619. PMID  34261451.
  11. ^ Renner, Susanne S. (2014). "The relative and absolute frequencies of angiosperm sexual systems: Dioecy, monoecy, gynodioecy, and an updated online database". American Journal of Botany. 101 (10): 1588–1596. doi: 10.3732/ajb.1400196. ISSN  1537-2197. PMID  25326608.
  12. ^ a b McDaniel, Stuart F.; Perroud, Pierre-François (2012). "Invited perspective: bryophytes as models for understanding the evolution of sexual systems". The Bryologist. 115 (1): 1–11. doi: 10.1639/0007-2745-115.1.1. ISSN  0007-2745. JSTOR  41486736. S2CID  85943617.
  13. ^ Genomes and Evolution of Charophytes, Bryophytes, Lycophytes and Ferns. Academic Press. 2016-03-23. p. 109. ISBN  978-0-12-801324-3.