Sexual system

For Linnaeus' sexual system, a classification of plants, see Linnaean taxonomy § Classification for plants.

Barnacles have a variety of sexual systems.

A sexual system is a distribution of male and female functions across organisms in a species.^[1][2] The terms reproductive system and mating system have also been used as synonyms.^[3]

Sexual systems play a key role in genetic variation and reproductive success, and may also have led to the origin or extinction of certain species.^[4] The distinctions between different sexual systems is not always clear due to phenotypic plasticity.^[2]

Interest in sexual systems goes back to Charles Darwin, who found that barnacles include some species that are androdioecious and some that are dioecious.^[5]

Types of sexual systems

See also: Plant reproductive morphology

The life cycle of an angiosperm.

Flowering plants may have dimorphic or monomorphic sexual systems. In monomorphic sexual systems, a combination of hermaphrodite, male, and/or female flowers may be present on the same plant. Monomorphic sexual systems include monoecy, gynomonoecy, andromonoecy, and trimonoecy. In dimorphic sexual systems, individual plants within a species only produce one sort of flower, either hermaphrodite or male, or female. Dimorphic sexual systems include dioecy, gynodioecy, androdioecy, and trioecy.^[6]

Male (a.k.a. staminate) flowers have a stamen but no pistil and produce only male gametes. Female (a.k.a. pistillate) flowers only have a pistil. Hermaphrodite (a.k.a. perfect, or bisexual) flowers have both a stamen and pistil. The sex of a single flower may differ from the sex of the whole organism: for example, a plant may have both staminate and pistillate flowers, making the plant as a whole a hermaphrodite. Hence although all monomorphic plants are hermaphrodites, different combinations of flower types (staminate, pistillate, or perfect) produces distinct monomorphic sexual systems.^[7]

In animals, androdioecy, gynodioecy, and trioecy are referred to as mixed sexual systems;^[8]where hermaphrodites coexist with single sexed individuals.^[9]

List of sexual systems

Sexual system	Description
Androdioecy	males and hermaphrodites coexist in a population.[10] It is rare in both plants and animals.[11]
Andromonoecy	rare sexual system in angiosperms, in which a plant has both male and hermaphroditic flowers.[12] It has been a subject of interest regarding the mechanism of sex expression.[13]
Dichogamy	an individual plant produces either exclusively male or exclusively female flowers at different points in time.[14] It is thought the temporal separation of producing male and female flowers occurs to prevent self-fertilization,[15] however this is debatable as dichogamy occurs in similar frequency among species which are self-compatible and self-incompatible.[16]
Dioicy	one of the main sexual systems in bryophytes.[17] In dioicy male and female sex organs are on separate gametophytes.[18]
Dioecy	a species has distinct individual organisms that are either male or female, i.e., they produce only male or only female gametes, either directly (in animals) or indirectly (in plants).[19]
Gonochorism	individuals are either male or female.[19] The term "gonochorism" is usually applied to animals while "dioecy" is applied to plants.[20] Gonochorism is the most common sexual system in animals, occurring in 95% of animal species.[21]
Gynodioecy	females and hermaphrodites coexist in the same population.[10]
Gynomonoecy	defined as the presence of both female and hermaphrodite flowers on the same individual of a plant species.[22] It is prevalent in Asteraceae but is poorly understood.[23]
Gynodioecy-Gynomonoecy	a sexual system for plants when female, hermaphrodite, and gynomonoecious plants coexist in the same population.[24]: 360
Monoicy	one of the main sexual systems in bryophytes.[17] In monoicy male and female sex organs are present in the same gametophyte.[18]
Monoecy	a sexual system in which male and female flowers are present on the same plant. It is common in angiosperms,[25] and occurs in 10% of all plant species.[26]^[dubious – discuss]
Sequential hermaphroditism	individuals start their adult lives as one sex, and change to the other sex at a later age.[27]
Sequential monoecy	a confusing sexual system,[28] in which the combination of male, female, and hermaphrodite flowers presented changes over time.[29] For example, some conifers produce exclusively either male or female cones when young, then both when older.[30] Sequential monoecy can be difficult to differentiate from dioecy.[31] Several alternative terms may be used in reference to sexual systems involving temporal changes to sex presentation of a plant species (e.g. dichogamy, sequential hermaphroditism, sex change, paradioecy, diphasy).[32]
Simultaneous hermaphroditism	an individual can produce both gamete types in the same breeding season.[33] Simultaneous hermaphroditism is one of the most common sexual systems in animals (though far less common than gonochorism) and is one of the most stable.[34]
Synoecy	all individuals in a population of flowering plants bear solely hermaphrodite flowers.[27]
Trioecy	males, females, and hermaphrodites exist in the same population.[8] It is present in both plants and animals but is always extremely rare.[35] Trioecy occurs in about 3.6% of flowering plants.[36] Trioecy may infrequently be referred to as tridioecy.[37]
Trimonoecy	(also called androgynomonoecy) is when male, female, and hermaphrodite flowers are present on the same plant.[27][38] Triomonoecy is rare.[39]

References

Footnotes

1. Encyclopedia of Animal Behavior. Vol. 4. Academic Press. 2019-01-21. p. 584. ISBN 978-0-12-813252-4.
2. Leonard 2019, p. 1.
3. Cardoso, João Custódio Fernandes; Viana, Matheus Lacerda; Matias, Raphael; Furtado, Marco Túlio; Caetano, Ana Paula de Souza; Consolaro, Hélder; Brito, Vinícius Lourenço Garcia de (Jul–Sep 2018). "Towards a unified terminology for angiosperm reproductive systems". Acta Botanica Brasilica. 32 (3): 329–348. doi:10.1590/0102-33062018abb0124. ISSN 0102-3306. S2CID 91470660.
4. Goldberg EE, Otto SP, Vamosi JC, Mayrose I, Sabath N, Ming R, Ashman TL (April 2017). "Macroevolutionary synthesis of flowering plant sexual systems". Evolution; International Journal of Organic Evolution. 71 (4): 898–912. doi:10.1111/evo.13181. PMID 28085192. S2CID 19562183.
5. Yusa Y, Yoshikawa M, Kitaura J, Kawane M, Ozaki Y, Yamato S, Høeg JT (March 2012). "Adaptive evolution of sexual systems in pedunculate barnacles". Proceedings. Biological Sciences. 279 (1730): 959–66. doi:10.1098/rspb.2011.1554. PMC 3259936. PMID 21881138.
6. Torices R, Méndez M, Gómez JM (April 2011). "Where do monomorphic sexual systems fit in the evolution of dioecy? Insights from the largest family of angiosperms". The New Phytologist. 190 (1): 234–248. Bibcode:2011NewPh.190..234T. doi:10.1111/j.1469-8137.2010.03609.x. PMID 21219336.
7. Jabbour, Florian; Espinosa, Felipe; Dejonghe, Quentin; Le Péchon, Timothée (2022-01-07). "Development and Evolution of Unisexual Flowers: A Review". Plants. 11 (2): 155. doi:10.3390/plants11020155. ISSN 2223-7747. PMC 8780417. PMID 35050043.
8. Oyarzún PA, Nuñez JJ, Toro JE, Gardner J (2020). "Trioecy in the Marine Mussel Semimytilus algosus (Mollusca, Bivalvia): Stable Sex Ratios Across 22 Degrees of a Latitudinal Gradient". Frontiers in Marine Science. 7. doi:10.3389/fmars.2020.00348. ISSN 2296-7745.
9. Leonard J, Cordoba-Aguilar A (2010-07-19). The Evolution of Primary Sexual Characters in Animals. Oxford University Press, USA. pp. 29–30. ISBN 978-0-19-532555-3.
10. Fusco G, Minelli A (2019-10-10). The Biology of Reproduction. Cambridge University Press. pp. 132–133. ISBN 978-1-108-49985-9.
11. Pontarotti P (2011-07-20). Evolutionary Biology – Concepts, Biodiversity, Macroevolution and Genome Evolution. Springer Science & Business Media. p. 36. ISBN 978-3-642-20763-1.
12. Casimiro-Soriguer R, Herrera J, Talavera S (March 2013). "Andromonoecy in an Old World Papilionoid legume, Erophaca baetica". Plant Biology. 15 (2): 353–9. Bibcode:2013PlBio..15..353C. doi:10.1111/j.1438-8677.2012.00648.x. PMID 22823201.
13. Pugnaire F, Valladares F (2007-06-20). Functional Plant Ecology. CRC Press. p. 524. ISBN 978-1-4200-0762-6.
14. Lloyd, David G.; Webb, C. J. (1986-07-01). "The avoidance of interference between the presentation of pollen and stigmas in angiosperms I. Dichogamy". New Zealand Journal of Botany. 24 (1): 135–162. Bibcode:1986NZJB...24..135L. doi:10.1080/0028825X.1986.10409725. ISSN 0028-825X.
15. Renner, Susanne S. (2014-10-01). "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. PMID 25326608.
16. Bertin, Robert I. (1993-05-01). "Incidence of Monoecy and Dichogamy in Relation to Self-Fertilization in Angiosperms". American Journal of Botany. 80 (5): 557–560. doi:10.1002/j.1537-2197.1993.tb13840.x. PMID 30139145.
17. Ramawat KG, Merillon JM, Shivanna KR (2016-04-19). Reproductive Biology of Plants. CRC Press. p. 62. ISBN 978-1-4822-0133-8.
18. Villarreal JC, Renner SS (November 2013). "Correlates of monoicy and dioicy in hornworts, the apparent sister group to vascular plants". BMC Evolutionary Biology. 13 (1): 239. Bibcode:2013BMCEE..13..239V. doi:10.1186/1471-2148-13-239. PMC 4228369. PMID 24180692.
19. King RC, Stansfield WD, Mulligan PK (2007). "Gonochorism". A Dictionary of Genetics. Oxford University Press. doi:10.1093/acref/9780195307610.001.0001. ISBN 978-0-19-530761-0. Retrieved 2021-07-28.
20. Encyclopedia of Evolutionary Biology. Vol. 2. Academic Press. 2016-04-14. p. 212. ISBN 978-0-12-800426-5.
21. Leonard JL (October 2013). "Williams' paradox and the role of phenotypic plasticity in sexual systems". Integrative and Comparative Biology. 53 (4): 671–88. doi:10.1093/icb/ict088. PMID 23970358.
22. Allaby M (2006). "Gynomonoecious". A Dictionary of Plant Sciences. Oxford University Press. doi:10.1093/acref/9780198608912.001.0001. ISBN 978-0-19-860891-2.
23. Martínez-Gómez P (2019-07-11). Plant Genetics and Molecular Breeding. MDPI. p. 442. ISBN 978-3-03921-175-3.
24. Lüttge, Ulrich; Cánovas, Francisco M.; Matyssek, Rainer (2016-05-27). Progress in Botany 77. Springer. ISBN 978-3-319-25688-7.
25. Bahadur B, Sujatha M, Carels N (2012-12-14). Jatropha, Challenges for a New Energy Crop: Volume 2: Genetic Improvement and Biotechnology. Springer Science & Business Media. pp. 27–28. ISBN 978-1-4614-4915-7.
26. Willmer P (2011-07-05). Pollination and Floral Ecology. Princeton University Press. p. 85. ISBN 978-1-4008-3894-3.
27. Beentje, Henk (2016). The Kew Plant Glossary (second ed.). Richmond, Surrey: Royal Botanic Gardens, Kew. ISBN 978-1-84246-604-9.
28. Putz, Francis E.; Mooney, Harold A. (1991). The Biology of Vines. Cambridge University Press. p. 411. ISBN 978-0-521-39250-1.
29. Flores-Rentería, Lluvia; Molina-Freaner, Francisco; Whipple, Amy V.; Gehring, Catherine A.; Domínguez, C. A. (2013-03-01). "Sexual stability in the nearly dioecious Pinus johannis (Pinaceae)". American Journal of Botany. 100 (3): 602–612. doi:10.3732/ajb.1200068. ISSN 0002-9122. PMID 23445824.
30. Kang, Hyesoon (2007-04-01). "Changes in gender expression in korean populations ofPinus densiflora over a five-year period". Journal of Plant Biology. 50 (2): 181–189. Bibcode:2007JPBio..50..181K. doi:10.1007/BF03030628. ISSN 1867-0725. S2CID 19890328.
31. Greenwood, Paul J.; Greenwood, Greenwood, Paul John; Harvey, Paul H.; Harvey, Reader in Biology Department of Zoology Paul H.; Slatkin, Montgomery; Slatkin, Professor of Integrative Biology Montgomery; Cambridge, University of (1985-07-11). Evolution: Essays in Honour of John Maynard Smith. CUP Archive. p. 240. ISBN 978-0-521-25734-3.
32. 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. ISBN 978-0-19-802192-6.
33. Leonard 2019, p. 14.
34. Leonard J, Cordoba-Aguilar A (2010-07-19). The Evolution of Primary Sexual Characters in Animals. Oxford University Press, USA. p. 20. ISBN 978-0-19-532555-3.
35. Leonard 2019, p. 23.
36. Albert B, Morand-Prieur MÉ, Brachet S, Gouyon PH, Frascaria-Lacoste N, Raquin C (October 2013). "Sex expression and reproductive biology in a tree species, Fraxinus excelsior L". Comptes Rendus Biologies. 336 (10): 479–85. doi:10.1016/j.crvi.2013.08.004. PMID 24246889.
37. Heikrujam, Monika; Sharma, Kuldeep; Prasad, Manoj; Agrawal, Veena (2015-01-01). "Review on different mechanisms of sex determination and sex-linked molecular markers in dioecious crops: a current update". Euphytica. 201 (2): 161–194. doi:10.1007/s10681-014-1293-z. ISSN 1573-5060. S2CID 254468003.
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Bibliography

Leonard, Janet (2019-05-21), Transitions Between Sexual Systems: Understanding the Mechanisms Of, and Pathways Between, Dioecy, Hermaphroditism and Other Sexual Systems, Springer Publishing, ISBN 978-3-319-94139-4