Editing Kin selection (section)

== In plants ==

=== Observations ===

Though originally thought unique to the [[Animal |animal kingdom]], evidence of kin selection has been identified in the [[Plant |plant kingdom]].<ref name="Karban et al 2013">{{Cite journal |last1=Karban |first1=Richard |last2=Shiojiri |first2=Kaori |last3=Ishizaki |first3=Satomi |last4=Wetzel |first4=William C. |last5=Evans |first5=Richard Y. |date=22 January 2013 |title=Kin recognition affects plant communication and defence |journal=Proceedings of the Royal Society B: Biological Sciences |volume=280 |issue=1756 |pages=20123062 |doi=10.1098/rspb.2012.3062 |pmc=3574382 |pmid=23407838}}</ref>

Competition for resources between developing zygotes in [[Ovary (botany)|plant ovaries]] increases when seeds had been pollinated with male gametes from different plants<!--'fathers'-->.<ref name="Bawa 2016">{{Cite journal |last=Bawa |first=Kamaljit S. |date=24 June 2016 |title=Kin selection and the evolution of plant reproductive traits |journal=Proceedings of the Royal Society B: Biological Sciences |volume=283 |issue=1842 |pages=20160789 |doi=10.1098/rspb.2016.0789 |pmc=5124086 |pmid=27852800}}</ref> How developing [[zygote]]s differentiate between full siblings and half-siblings in the ovary is undetermined, but [[Genetics|genetic]] interactions are thought to play a role.<ref name="Bawa 2016"/> Nonetheless, competition between [[zygote]]s in the ovary is detrimental to the [[reproductive success]] of the (female) plant, and fewer zygotes mature into seeds.<ref name="Bawa 2016"/> As such, the reproductive traits and behaviors of plants suggests the [[evolution]] of behaviors and characteristics that increase the genetic relatedness of fertilized eggs in the plant ovary, thereby fostering kin selection and cooperation among the seeds as they develop. These traits differ among plant species. Some species have evolved to have fewer [[ovule]]s per ovary, commonly one ovule per ovary, thereby decreasing the chance of developing multiple, differently fathered seeds within the same ovary.<ref name="Bawa 2016"/> Multi-ovulated plants have developed mechanisms that increase the chances of all ovules within the ovary being fathered by the same parent. Such mechanisms include dispersal of [[pollen]] in aggregated packets and closure of the [[Stigma (botany)|stigmatic]] lobes after pollen is introduced.<ref name="Bawa 2016"/> The aggregated pollen packet releases pollen gametes in the ovary, thereby increasing likelihood that all ovules are fertilized by pollen from the same parent.<ref name="Bawa 2016"/> Likewise, the closure of the ovary pore prevents entry of new pollen.<ref name="Bawa 2016"/> Other multi-ovulated plants have evolved mechanisms that mimic the evolutionary adaption of single-ovulated ovaries; the ovules are fertilized by pollen from different individuals, but the mother ovary then selectively [[Abortion|aborts]] fertilized ovules, either at the zygotic or [[embryo]]nic stage.<ref name="Bawa 2016"/>

[[File:Ipomoea hederacea 001.JPG|thumb|Morning glory plants grow smaller roots when next to kin than to non-kin plants.]]

After seeds are dispersed, kin recognition and cooperation affects root formation in developing plants.<ref name="Biernaskie 2010">{{Cite journal |last=Biernaskie |first=Jay M. |date=8 December 2010 |title=Evidence for competition and cooperation among climbing plants |journal=Proceedings of the Royal Society B: Biological Sciences |volume=278 |issue=1714 |pages=1989–1996 |doi=10.1098/rspb.2010.1771 |issn=0962-8452 |pmc=3107641 |pmid=21147795}}</ref> Studies have found that the total root mass developed by [[Ipomoea hederacea|''Ipomoea hederacea'' (morning glory shrubs)]] grown next to kin is significantly smaller than those grown next to non-kin;<ref name="Biernaskie 2010"/><ref name="Dudley File 2007">{{Cite journal |last1=Dudley |first1=Susan A. |last2=File |first2=Amanda L. |date=13 June 2007 |title=Kin recognition in an annual plant |journal=Biology Letters |volume=3 |issue=4 |pages=435–438 |doi=10.1098/rsbl.2007.0232 |issn=1744-9561 |pmc=2104794 |pmid=17567552}}</ref> shrubs grown next to kin thus allocate less energy and resources to growing the larger root systems needed for competitive growth. When seedlings were grown in individual pots placed next to kin or non-kin relatives, no difference in root growth was observed.<ref name="Dudley File 2007"/> This indicates that kin recognition occurs via signals received by the roots.<ref name="Dudley File 2007"/> Further, groups of ''I. hederacea'' plants are more varied in height when grown with kin than when grown with non-kin.<ref name="Biernaskie 2010"/> The evolutionary benefit provided by this was further investigated by researchers at the [[University of Montpellier|Université de Montpellier]]. They found that the alternating heights seen in kin-grouped [[crop]]s allowed for optimal light availability to all plants in the group; shorter plants next to taller plants had access to more light than those surrounded by plants of similar height.<ref name="Montazeaud Rousset Fort 2020">{{Cite journal |last1=Montazeaud |first1=Germain |last2=Rousset |first2=François |last3=Fort |first3=Florian |last4=Violle |first4=Cyrille |last5=Fréville |first5=Hélène |last6=Gandon |first6=Sylvain |date=22 January 2020 |title=Farming plant cooperation in crops |journal=Proceedings of the Royal Society B: Biological Sciences |volume=287 |issue=1919 |pages=20191290 |doi=10.1098/rspb.2019.1290 |pmc=7015324 |pmid=31964305}}</ref>

The above examples illustrate the effect of kin selection in the equitable allocation of light, nutrients, and water. The evolutionary emergence of single-ovulated ovaries in plants has eliminated the need for a developing seed to compete for nutrients, thus increasing its chance of survival and [[germination]].<ref name="Bawa 2016"/> Likewise, the fathering of all ovules in multi-ovulated ovaries by one father, decreases the likelihood of competition between developing seeds, thereby also increasing the seeds' chances of survival and germination.<ref name="Bawa 2016"/> The decreased root growth in plants grown with kin increases the amount of energy available for reproduction; plants grown with kin produced more seeds than those grown with non-kin.<ref name="Biernaskie 2010"/><ref name="Dudley File 2007"/> Similarly, the increase in light made available by alternating heights in groups of related plants is associated with higher fecundity.<ref name="Biernaskie 2010"/><ref name="Montazeaud Rousset Fort 2020"/>

Kin selection has also been observed in plant responses to herbivory. In an experiment done by Richard Karban et al., leaves of potted [[Artemisia tridentata|''Artemisia tridentata'' (sagebrushes)]] were clipped with scissors to simulate herbivory. The gaseous [[Green leaf volatiles|volatiles]] emitted by the clipped leaves were captured in a plastic bag. When these volatiles were transferred to leaves of a closely related sagebrush, the recipient experienced lower levels of herbivory than those that had been exposed to volatiles released by non-kin plants.<ref name="Karban et al 2013"/> Sagebrushes do not uniformly emit the same volatiles in response to herbivory: the chemical ratios and composition of emitted volatiles vary from one sagebrush to another.<ref name="Karban et al 2013"/><ref>{{Cite journal |last1=Karban |first1=Richard |last2=Shiojiri |first2=Kaori |date=15 May 2009 |title=Self-recognition affects plant communication and defense |journal=Ecology Letters |volume=12 |issue=6 |pages=502–506 |doi=10.1111/j.1461-0248.2009.01313.x |pmid=19392712 |pmc=3014537|bibcode=2009EcolL..12..502K }}</ref> Closely related sagebrushes emit similar volatiles, and the similarities decrease as relatedness decreases.<ref name="Karban et al 2013"/> This suggests that the composition of volatile gasses plays a role in kin selection among plants. Volatiles from a distantly related plant are less likely to induce a [[Plant defense against herbivory|protective response against herbivory]] in a neighboring plant, than volatiles from a closely related plant.<ref name="Karban et al 2013"/> This fosters kin selection, as the volatiles emitted by a plant will activate the herbivorous defense response in related plants only, thus increasing their chance of survival and reproduction.<ref name="Karban et al 2013"/>

Kin selection may play a role in plant-pollinator interactions, especially because pollinator attraction is influenced not only by floral displays, but by the spatial arrangement of plants in a group, which is referred to as the "magnet effect".<ref name=":0">{{Cite journal |last1=Torices |first1=Rubén |last2=Gómez |first2=José M. |last3=Pannell |first3=John R. |date=2018 |title=Kin discrimination allows plants to modify investment towards pollinator attraction |journal=Nature Communications |language=en |volume=9 |issue=1 |pages=2018 |doi=10.1038/s41467-018-04378-3 |issn=2041-1723 |pmc=5964244 |pmid=29789560|bibcode=2018NatCo...9.2018T }}</ref> For example, in an experiment performed on ''[[Moricandia]] moricandioides'', Torices et al. demonstrated that focal plants in the presence of kin show increased advertising effort (defined as total petal mass of plants in a group divided by the plant biomass) compared to those in the presence of non-kin, and that this effect is greater in larger groups.<ref name=":0" /> ''M. moricandioides'' is a good model organism for the study of plant-pollinator interactions because it relies on pollinators for reproduction, as it is self-incompatible.<ref name=":0" /> The study design for this experiment included planting establishing pots of ''M. moricandioides'' with zero, three or six neighbors (either unrelated or half-sib progeny of the same mother) and advertising effort was calculated after 26 days of flowering.<ref name=":0" /> The exact mechanism of kin recognition in ''M. moricandioides'' is unknown, but possible mechanisms include above-ground communication with volatile compounds,<ref>{{Cite journal |last1=Karban |first1=Richard |last2=Shiojiri |first2=Kaori |last3=Ishizaki |first3=Satomi |last4=Wetzel |first4=William C. |last5=Evans |first5=Richard Y. |date=2013-04-07 |title=Kin recognition affects plant communication and defence |journal=Proceedings of the Royal Society B: Biological Sciences |volume=280 |issue=1756 |pages=20123062 |doi=10.1098/rspb.2012.3062 |pmid=23407838 |pmc=3574382 |issn=0962-8452}}</ref> or below-ground communication with root exudates.<ref>{{Cite journal |last1=Semchenko |first1=Marina |last2=Saar |first2=Sirgi |last3=Lepik |first3=Anu |date=2014-07-10 |title=Plant root exudates mediate neighbour recognition and trigger complex behavioural changes |journal=New Phytologist |volume=204 |issue=3 |pages=631–637 |doi=10.1111/nph.12930 |pmid=25039372 |issn=0028-646X|doi-access=free |bibcode=2014NewPh.204..631S }}</ref>

=== Mechanisms in plants ===

The ability to differentiate between kin and non-kin is not necessary for kin selection in many animals.<ref name="File Murphy Dudley 2011">{{Cite journal |last1=File |first1=Amanda L. |last2=Murphy |first2=Guillermo P. |last3=Dudley |first3=Susan A. |date=9 November 2011 |title=Fitness consequences of plants growing with siblings: reconciling kin selection, niche partitioning and competitive ability |journal=Proceedings of the Royal Society B: Biological Sciences |volume=279 |issue=1727 |pages=209–218 |doi=10.1098/rspb.2011.1995 |issn=0962-8452 |pmc=3223689 |pmid=22072602}}</ref> However, because plants do not reliably germinate in close proximity to kin, it is thought that, within the plant kingdom, kin recognition is especially important for kin selection there, but the mechanism remains unknown.<ref name="File Murphy Dudley 2011"/><ref>{{Cite journal |last1=Dam |first1=Nicole M. van |last2=Bouwmeester |first2=Harro J. |date=March 2016 |title=Metabolomics in the Rhizosphere: Tapping into Belowground Chemical Communication |url=https://www.cell.com/trends/plant-science/abstract/S1360-1385(16)00009-1 |journal=Trends in Plant Science |volume=21 |issue=3 |pages=256–265 |doi=10.1016/j.tplants.2016.01.008 |issn=1360-1385 |pmid=26832948|bibcode=2016TPS....21..256V |url-access=subscription }}</ref>

One proposed mechanism for kin recognition involves communication through roots, with secretion and reception of [[Plant root exudates|root exudates]].<ref name="File Murphy Dudley 2011"/><ref name="Rahman Zhou Wu 2019">{{Cite journal |last1=Rahman |first1=Muhammad Khashi u |last2=Zhou |first2=Xingang |last3=Wu |first3=Fengzhi |date=5 Aug 2019 |title=The role of root exudates, CMNs, and VOCs in plant–plant interaction |journal=Journal of Plant Interactions |volume=14 |issue=1 |pages=630–636 |doi=10.1080/17429145.2019.1689581 |issn=1742-9145 |doi-access=free|bibcode=2019JPlaI..14..630K }}</ref><ref name="Biedrzycki Julany Dudley 2010">{{Cite journal |last1=Biedrzycki |first1=Meredith L. |last2=Jilany |first2=Tafari A. |last3=Dudley |first3=Susan A. |last4=Bais |first4=Harsh P. |date=Jan–Feb 2010 |title=Root exudates mediate kin recognition in plants |journal=Communicative & Integrative Biology |volume=3 |issue=1 |pages=28–35 |doi=10.4161/cib.3.1.10118 |issn=1942-0889 |pmc=2881236 |pmid=20539778}}</ref><ref name="Yang Li Xu 2018">{{Cite journal |last1=Yang |first1=Xue-Fang |last2=Li |first2=Lei-Lei |last3=Xu |first3=You |last4=Kong |first4=Chui-Hua |date=October 2018 |title=Kin recognition in rice ( Oryza sativa) lines |journal=New Phytologist  |volume=220 |issue=2 |pages=567–578 |doi=10.1111/nph.15296 |pmid=29956839 |s2cid=49590796 |doi-access=free |bibcode=2018NewPh.220..567Y }}</ref> This would require exudates to be actively secreted by roots of one plant, and detected by roots of neighboring plants.<ref name="Rahman Zhou Wu 2019"/><ref name="Biedrzycki Julany Dudley 2010"/> The root exudate allantoin produced by rice plants, ''[[Oryza sativa]]'', has been documented to be in greater production when growing next to cultivars that are largely unrelated.<ref name="Yang Li Xu 2018" /><ref name="Anten Chen 2021">{{Cite journal |last1=Anten |first1=Niels P. R. |last2=Chen |first2=Bin J. W. |date=April 2021 |title=Detect thy family: Mechanisms, ecology and agricultural aspects of kin recognition in plants |journal=Plant, Cell & Environment|volume=44 |issue=4 |pages=1059–1071 |doi=10.1111/pce.14011 |pmc=8048686 |pmid=33522615|bibcode=2021PCEnv..44.1059A }}</ref> High production levels of Allantoin correlated to up regulation of auxin and auxin transporters, resulting in increased lateral root development and directional growth of their roots towards non kin, maximizing competition.<ref name="Yang Li Xu 2018" /><ref name="Anten Chen 2021" /> This is mainly not observed in ''Oryza Sativa'' when surrounded by kin, invoking altruistic behaviors to promote inclusive fitness.<ref name="Yang Li Xu 2018" /> However the root [[Receptor (biochemistry)|receptors]] responsible for recognition of kin exudates, and the pathway induced by receptor activation, remain unknown.<ref name="Biedrzycki Julany Dudley 2010"/> The [[mycorrhiza]] associated with roots might facilitate reception of exudates, but again the mechanism is unknown.<ref>{{Cite journal |last1=Johnson |first1=David |last2=Gilbert |first2=Lucy |date=12 September 2014 |title=Interplant signalling through hyphal networks |journal=New Phytologist |language=en |volume=205 |issue=4 |pages=1448–1453 |doi=10.1111/nph.13115 |pmid=25421970 |doi-access=free}}</ref>

Another possibility is communication through [[green leaf volatiles]]. Karban et al. studied kin recognition in sagebrushes, ''[[Artemisia tridentata]]''. The volatile-donating sagebrushes were kept in individual pots, separate from the plants that received the volatiles, finding that plants responded to [[herbivore]] damage to a neighbour's leaves. This suggests that root signalling is not necessary to induce a [[Plant defense against herbivory|protective response against herbivory]] in neighbouring kin plants. Karban et al. suggest that plants may be able to differentiate between kin and non-kin based on the composition of volatiles. Because only the recipient sagebrush's leaves were exposed<ref name="Karban et al 2013"/> the volatiles presumably activated a [[Receptor (biochemistry)|receptor protein]] in the plant's leaves. The identity of this receptor, and the signalling pathway triggered by its activation, both remain to be discovered.<ref>{{Cite journal |last1=Bouwmeester |first1=Harro |last2=Schuurink |first2=Robert C. |last3=Bleeker |first3=Petra M. |last4=Schiestl |first4=Florian |date=Dec 2019 |title=The role of volatiles in plant communication |journal=The Plant Journal |volume=100 |issue=5 |pages=892–907 |doi=10.1111/tpj.14496 |issn=0960-7412 |pmc=6899487 |pmid=31410886}}</ref>