Hubbry Logo
Self-pollinationSelf-pollinationMain
Open search
Self-pollination
Community hub
Self-pollination
logo
8 pages, 0 posts
0 subscribers
Be the first to start a discussion here.
Be the first to start a discussion here.
Self-pollination
Self-pollination
Self-pollination
View on Wikipedia
from Wikipedia
One type of automatic self-pollination occurs in the orchid Ophrys apifera. One of the two pollinia bends itself towards the stigma.

Self-pollination is a form of pollination in which pollen arrives at the stigma of a flower (in flowering plants) or at the ovule (in gymnosperms) of the same plant. The term cross-pollination is used for the opposite case, where pollen from one plant moves to a different plant.

There are two types of self-pollination: in autogamy, pollen is transferred to the stigma of the same flower; in geitonogamy, pollen is transferred from the anther of one flower to the stigma of another flower on the same flowering plant, or from microsporangium to ovule within a single (monoecious) gymnosperm. Some plants have mechanisms that ensure autogamy, such as flowers that do not open (cleistogamy), or stamens that move to come into contact with the stigma.

The term selfing that is often used as a synonym is not limited to self-pollination, but also applies to other types of self-fertilization.

Occurrence

[edit]

Few plants self-pollinate without the aid of pollen vectors (such as wind or insects). The mechanism is seen most often in some legumes such as peanuts. In another legume, soybeans, the flowers open and remain receptive to insect cross pollination during the day. If this is not accomplished, the flowers self-pollinate as they are closing. Among other plants that can self-pollinate are many kinds of orchids, peas, sunflowers and tridax. Most of the self-pollinating plants have small, relatively inconspicuous flowers that shed pollen directly onto the stigma, sometimes even before the bud opens. Self-pollinated plants expend less energy in the production of pollinator attractants and can grow in areas where the kinds of insects or other animals that might visit them are absent or very scarce—as in the Arctic or at high elevations.

Self-pollination limits the variety of progeny and may depress plant vigor. However, self-pollination can be advantageous, allowing plants to spread beyond the range of suitable pollinators or produce offspring in areas where pollinator populations have been greatly reduced or are naturally variable.[1]

Pollination can also be accomplished by cross-pollination. Cross-pollination is the transfer of pollen, by wind or animals such as insects and birds, from the anther to the stigma of flowers on separate plants.

Types of self-pollinating flowers

[edit]

Both hermaphrodite and monoecious species have the potential for self-pollination leading to self-fertilization unless there is a mechanism to avoid it. 80% of all flowering plants are hermaphroditic, meaning they contain both sexes in the same flower, while 5 percent of plant species are monoecious. The remaining 15% would therefore be dioecious (each plant unisexual). Plants that self-pollinate include several types of orchids, and sunflowers. Dandelions are capable of self-pollination as well as cross-pollination.

Advantages

[edit]

There are several advantages for self-pollinating flowers. Firstly, if a given genotype is well-suited for an environment, self-pollination helps to keep this trait stable in the species. Not being dependent on pollinating agents allows self-pollination to occur when bees and wind are nowhere to be found. Self-pollination or cross pollination can be an advantage when the number of flowers is small or they are widely spaced. During self-pollination, the pollen grains are not transmitted from one flower to another. As a result, there is less wastage of pollen. Also, self-pollinating plants do not depend on external carriers. They also cannot make changes in their characters and so the features of a species can be maintained with purity. Self-pollination also helps to preserve parental characters as the gametes from the same flower are evolved. It is not necessary for flowers to produce nectar, scent, or to be colourful in order to attract pollinators.

Disadvantages

[edit]

The disadvantages of self-pollination come from a lack of variation that allows no adaptation to the changing environment or potential pathogen attack. Self-pollination can lead to inbreeding depression caused by expression of deleterious recessive mutations,[2] or to the reduced health of the species, due to the breeding of related specimens. This is why many flowers that could potentially self-pollinate have a built-in mechanism to avoid it, or make it second choice at best. Genetic defects in self-pollinating plants cannot be eliminated by genetic recombination and offspring can only avoid inheriting the deleterious attributes through a chance mutation arising in a gamete.

Mixed mating

[edit]

About 42% of flowering plants exhibit a mixed mating system in nature.[3] In the most common kind of system, individual plants produce a single flower type and fruits may contain self-pollinated, out-crossed or a mixture of progeny types. Another mixed mating system is referred to as dimorphic cleistogamy. In this system a single plant produces both open, potentially out-crossed and closed, obligately self-pollinated cleistogamous flowers.[4]

Example species

[edit]

The evolutionary shift from outcrossing to self-fertilization is one of the most common evolutionary transitions in plants. About 10-15% of flowering plants are predominantly self-fertilizing.[5] A few well-studied examples of self-pollinating species are described below.

Orchids

[edit]

Self-pollination in the slipper orchid Paphiopedilum parishii occurs when the anther changes from a solid to a liquid state and directly contacts the stigma surface without the aid of any pollinating agent.[6]

The tree-living orchid Holcoglossum amesianum has a type of self-pollination mechanism in which the bisexual flower turns its anther against gravity through 360° in order to insert pollen into its own stigma cavity—without the aid of any pollinating agent or medium. This type of self-pollination appears to be an adaptation to the windless, drought conditions that are present when flowering occurs, at a time when insects are scarce.[7] Without pollinators for outcrossing, the necessity of ensuring reproductive success appears to outweigh potential adverse effects of inbreeding. Such an adaptation may be widespread among species in similar environments.

Self-pollination in the Madagascan orchid Bulbophyllum bicoloratum occurs by virtue of a rostellum that may have regained its stigmatic function as part of the distal median stigmatic lobe.[8]

Caulokaempferia coenobialis

[edit]

In the Chinese herb Caulokaempferia coenobialis a film of pollen is transported from the anther (pollen sacs) by an oily emulsion that slides sideways along the flower's style and into the individual's own stigma.[9] The lateral flow of the film of pollen along the style appears to be due solely to the spreading properties of the oily emulsion and not to gravity. This strategy may have evolved to cope with a scarcity of pollinators in the extremely shady and humid habitats of C. coenobialis.

Capsella rubella

[edit]

Capsella rubella (Red Shepherd's Purse)[10][11] is a self-pollinating species that became self-compatible 50,000 to 100,000 years ago, indicating that self-pollination is an evolutionary adaptation that can persist over many generations. Its out-crossing progenitor was identified as Capsella grandiflora.

Arabidopsis thaliana

[edit]

Arabidopsis thaliana is a predominantly self-pollinating plant with an out-crossing rate in the wild estimated at less than 0.3%.[12] A study suggested that self-pollination evolved roughly a million years ago or more.[13]

Tomato

[edit]

In the tomato plant, cleistogamy, a form of automatic self-pollination, is promoted by a modification of floral structures.[14] This modification involves formation of a stigma enclosing floral structure.[14]

Possible long-term benefit of meiosis

[edit]

Meiosis followed by self-pollination produces little overall genetic variation. This raises the question of how meiosis in self-pollinating plants is adaptively maintained over extended periods (i.e. for roughly a million years or more, as in the case of A. thaliana)[13] in preference to a less complicated and less costly asexual ameiotic process for producing progeny. An adaptive benefit of meiosis that may explain its long-term maintenance in self-pollinating plants is efficient recombinational repair of DNA damage.[15] This benefit can be realized at each generation (even when genetic variation is not produced).

See also

[edit]

References

[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Self-pollination

View on Grokipedia
from Grokipedia
Self-pollination is the transfer of from the anther to the stigma within the same flower () or between flowers on the same plant (), leading to self-fertilization in flowering plants. This process occurs primarily in hermaphroditic flowers where reproductive organs mature simultaneously, allowing to contact the stigma without external agents, though mechanisms like systems can prevent it in some to promote . Self-pollination has evolved repeatedly from ancestors, often providing reproductive assurance in environments with unreliable pollinators, but it is counterbalanced by evolutionary traits favoring . Key advantages include reduced dependence on pollinators, minimal pollen wastage, and preservation of desirable traits across generations, enabling reliable production in stable habitats. However, it carries significant disadvantages, such as decreased that limits adaptation to diseases or environmental changes, and increased risk of , where selfed offspring exhibit reduced fitness due to homozygous deleterious alleles. These trade-offs influence the prevalence of self-pollination in approximately 10-15% of angiosperm species, with higher rates in isolated or colonizing populations. Examples of self-pollinating plants include many crops like , , where the trait supports uniform yields but underscores the need for breeding programs to introduce diversity. In evolutionary terms, selfing offers a transmission advantage for self-compatibility alleles but can lead to long-term lineage decline without occasional .

Fundamentals

Definition

Self-pollination is a reproductive in flowering whereby pollen grains are transferred from the anther of a flower to the stigma of the same flower or to the stigma of another flower on the same , enabling fertilization without reliance on external agents such as or pollinators. This mechanism contrasts with cross-pollination, or , which requires pollen transfer between genetically distinct to achieve fertilization and promotes in offspring. In angiosperms, self-pollination represents a form of that can occur autonomously within the flower structure, contributing to production in environments where pollinators are scarce. Key subtypes include autogamy, defined as the transfer of pollen to the stigma within the same flower, and geitonogamy, which involves pollen movement between flowers of the same plant but may still require pollinator assistance. The term "self-pollination" derives from the English prefix "self-" combined with "pollination," the latter rooted in Latin pollinare meaning "to furnish with pollen," while related Greek-derived terms like "autogamy" incorporate auto- ("self") and -gamy ("marriage" or "fertilization"). The phenomenon was first systematically observed and documented by the German botanist Christian Konrad Sprengel in his 1793 work Das entdeckte Geheimnis der Natur im Bau und in der Befruchtung der Blumen, where he explored floral adaptations for pollination, including instances of self-fertilization alongside insect-mediated cross-pollination.

Occurrence

Self-pollination is a reproductive strategy observed in a substantial proportion of angiosperm species, with approximately half exhibiting self-compatibility that enables it, although only 10–15% are predominantly self-fertilizing. This capability allows pollen transfer within the same flower or plant, facilitating reproduction even in the absence of external pollinators. The prevalence increases notably in isolated or stressful environments, such as oceanic islands or arid regions, where pollinator scarcity or mate limitation selects for selfing as a means of reproductive assurance. Ecologically, self-pollination is particularly favored in habitats characterized by low pollinator density, including high-altitude regions, , and post-disturbance sites where resources are ephemeral or fragmented. In such conditions, the strategy ensures production despite unreliable biotic pollination services, as seen in adapting to sparse activity or in recovering ecosystems following fires or floods. These triggers highlight self-pollination's role in enabling persistence in marginal niches, where outcrossing opportunities are limited. Taxonomically, self-pollination is common in certain families, including (grasses), where species like (Triticum aestivum) and () rely on it through cleistogamous or enclosed inflorescences. In (legumes), it prevails in many cultivated forms such as peas (Pisum sativum), often via bud pollination before flowers open. Similarly, (nightshades) features self-pollination in crops like tomatoes (Solanum lycopersicum), supported by anther-stigma proximity. Conversely, it is rare in families with elaborate, showy flowers, such as Orchidaceae, where most species depend on specialized interactions unless rare cleistogamous adaptations occur. The occurrence of self-pollination has arisen through multiple independent evolutionary origins across lineages, frequently associated with the of novel or challenging habitats that impose selective pressures for reproductive . This repeated transition underscores its adaptive value in diverse ecosystems, from continental expansions to insular invasions.

Mechanisms

Autogamy

is the transfer of grains from the anther to the stigma within the same flower, serving as the primary and most direct mechanism of self-pollination in hermaphroditic flowers. This process typically occurs in bisexual flowers where male and female reproductive organs are present simultaneously, enabling fertilization without external agents. Subtypes of autogamy include direct physical contact between the anther and stigma, as well as indirect transfer facilitated by , where grains fall onto the stigma. Floral adaptations in autogamous species often emphasize precise timing to ensure efficient pollen deposition. For instance, the stigma may become receptive prior to anther dehiscence, allowing pollen to contact a viable surface immediately upon release and promoting prior selfing before the flower fully opens. Bud pollination exemplifies this adaptation, where self-pollination transpires in the closed bud stage, minimizing exposure to external pollinators and enhancing reproductive assurance in pollinator-scarce environments. Such mechanisms are particularly evident in species like Collinsia parviflora, where smaller flowers exhibit reduced herkogamy—the spatial separation between anthers and stigma—leading to higher rates of autonomous selfing. Genetically, autogamy results in an immediate increase in homozygosity among progeny, as the offspring inherit identical alleles from a single parental fusion, accelerating the fixation of homozygous genotypes across generations. This contrasts with by promoting and reducing heterozygosity from the outset. Autogamy prevails as the dominant mode of self-pollination, especially in small, inconspicuous flowers that lack elaborate displays or rewards to attract pollinators, thereby conserving resources while ensuring production. These floral traits correlate with faster developmental timing and higher selfing efficiency, as observed in numerous and adapted to or resource-limited habitats.

Geitonogamy and Cleistogamy

refers to the transfer of from the anther of one flower to the stigma of another flower on the same , a process that results in self-fertilization despite involving inter-flower movement similar to cross-pollination mechanisms. This form of self-pollination is commonly mediated by pollinators, such as , or abiotic agents like , particularly in with large inflorescences where sequential flower visits increase the likelihood of within-plant pollen transfer. Genetically, is equivalent to as it unites gametes from the same individual, but it can create an illusion of at the population level since pollen dispersal mimics xenogamy; however, it often leads to pollen wastage by diverting resources that could facilitate between . In species like (common milkweed), high rates of mediated by pollinators have been shown to significantly reduce fruit set due to to aborted selfed seeds. Unlike , which occurs within a single flower, requires plant-level pollen mobility and is more prevalent in larger individuals or those with extended flowering periods, as pollinators tend to forage sequentially within displays, elevating self- deposition on stigmas. For instance, in Ipomopsis aggregata, flowers on larger receive proportionally more self- via , leading to higher selfing rates compared to smaller . This mechanism can impose costs in self-compatible species by increasing competition between self- and outcross- on stigmas, potentially reducing overall . Cleistogamy involves self-pollination and fertilization entirely within unopened, bud-like flowers that remain closed throughout their development, ensuring autonomous without reliance on external . These cleistogamous flowers are typically reduced in size, with fused or absent petals, minimal production, and internal anther dehiscence that deposits directly onto the stigma, often facilitated by mechanical pressure from elongating filaments. This adaptation is energy-efficient, as it minimizes investment in floral attractants and structures for access, often producing smaller but with comparable or higher seed set efficiency due to guaranteed . Cleistogamy has evolved independently in approximately 693 across 50 families (as of 2007), providing reproductive assurance in environments with unreliable pollinators or sparse populations. In many cleistogamous species, plants exhibit dimorphism by producing both cleistogamous flowers for obligatory selfing and larger chasmogamous (open) flowers capable of , allowing flexible based on environmental cues such as nutrient availability or stress. For example, in Viola species (violets), cleistogamous flowers form underground or in leaf axils with tightly appressed structures that prevent opening, while chasmogamous flowers appear aboveground for potential pollinator-mediated . Similarly, the Arachis hypogaea () primarily reproduces via cleistogamous flowers that develop below ground after peg elongation, ensuring seed production in nutrient-poor soils. Some plants integrate geitonogamy and cleistogamy as complementary strategies within mixed-mating systems, shifting allocation toward cleistogamous reproduction under resource limitation while relying on geitonogamous selfing in open flowers during favorable conditions. In Polygala lewtonii, for instance, the production of cleistogamous flowers increases with competition and drought, supplementing geitonogamous selfing in chasmogamous inflorescences to maintain seed output. This dual approach highlights how inter-flower pollen transfer in geitonogamy contrasts with the fully enclosed, intra-flower process of cleistogamy, both enhancing selfing reliability beyond single-flower autogamy.

Evolutionary Aspects

Advantages

Self-pollination provides reproductive assurance by enabling plants to achieve fertilization and production independently of external or mates, which is particularly beneficial in environments where activity is limited or unreliable. This mechanism ensures higher set compared to in such conditions, with studies demonstrating that autonomous selfing can increase production by an average of 84% in alpine populations facing limitation. For instance, in alpine environments with scarce , autonomous selfing has been shown to account for the majority of fruit and set, preventing reproductive failure. In terms of efficiency, self-pollinating plants allocate fewer resources to producing elaborate floral attractants such as , scents, or large displays, allowing them to redirect toward growth, seed development, and survival. This reduced investment in structures often results in smaller, less conspicuous flowers, which lowers overall reproductive costs and enables faster generation times, facilitating quicker maturation and in resource-limited settings. Self-pollination supports by allowing single individuals to establish new populations in novel or isolated habitats, as a lone propagule can produce viable offspring without requiring compatible mates. This capability increases the success of founder events and , particularly for invading disturbed or remote areas, where populations might fail due to mate scarcity. Field studies provide of higher fitness for self-pollinating plants during , where exacerbates pollen limitation, but selfing maintains seed output and plant survival. For example, in water-stressed conditions, self-compatible species exhibit greater through assured seed set, enabling drought escape via rapid life cycles and reduced dependence on fluctuating services.

Disadvantages

Self-pollination often results in , characterized by reduced heterozygosity and the expression of deleterious recessive alleles, leading to lower fitness in offspring compared to outcrossed progeny. In , meta-analyses indicate that inbreeding depression causes fitness reductions across various traits, though this can vary widely depending on the and environmental conditions. Over successive generations, selfing accelerates the accumulation of deleterious alleles due to decreased and weakened purifying selection, further exacerbating fitness declines. Many plant species have evolved self-incompatibility (SI) systems to prevent self-pollination and mitigate these genetic risks. In gametophytic SI, common in families like Solanaceae and Rosaceae, the S-locus encodes pistil-specific S-RNases that recognize and reject self-pollen by degrading its RNA, blocking fertilization. For selfing to occur in SI species, these mechanisms must break down through mutations or environmental factors, such as high temperatures or pollinator scarcity, allowing self-compatible lineages to arise but often at the cost of increased inbreeding. Ecologically, self-pollination reduces within populations, limiting their ability to adapt to environmental changes like pathogens, shifts, or alterations. Low heterozygosity impairs evolutionary potential, making selfing populations more susceptible to local during stressors that favor novel genetic combinations. Historical examples illustrate these risks; similarly, modeling studies on demonstrate that from self-fertilization can shorten population persistence times by 25-30%, contributing to higher overall probabilities in small, isolated groups.

Mixed Mating Systems

Mixed mating systems in involve a combination of self-pollination and cross-pollination, resulting in variable selfing rates typically ranging from 0.2 to 0.8 within populations. These systems often arise through partial self-compatibility, where are not fully self-incompatible but exhibit reduced success in self-fertilization compared to , allowing flexibility in reproductive strategies. Selfing rates in such systems can be modulated by environmental cues, such as availability or stress conditions, or by genetic factors that influence pollen-pistil interactions. The adaptive value of mixed mating lies in balancing the reproductive assurance provided by selfing—ensuring seed production in the absence of mates or pollinators—with the gained from , which mitigates . This equilibrium is particularly evident in colonizing species, as described by Baker's Law, which posits that self-compatible are more likely to successfully establish in new habitats due to their ability to reproduce from single individuals. Empirical studies across global floras confirm that species with higher self-compatibility indices exhibit greater success, supporting the role of mixed mating in invasion biology. Mechanisms regulating mixed mating include delayed selfing, where flowers first facilitate via pollinators before autonomously self-pollinating if unvisited, often through architectural features like stigma retraction or shedding. Many produce both chasmogamous (open, outcrossing-favoring) and cleistogamous (closed, self-pollinating) flowers, enabling context-dependent mating; for instance, cleistogamous flowers predominate under resource limitation to prioritize selfing. At the genetic level, loci such as the S-locus inhibitor (Sli) gene promote partial self-compatibility by overriding responses, allowing controlled self-fertilization in otherwise outcrossing lineages. In , outcrossing rates in mixed systems are commonly estimated using allozyme markers to analyze progeny arrays, revealing multilocus outcrossing rates (t_m) that vary by population but average around 0.6 in many herbaceous species. These markers help quantify the proportion of selfed versus outcrossed offspring, demonstrating how ecological factors like density influence dynamics without requiring full genomic sequencing.

Examples

Crop Plants

The (Solanum lycopersicum) is primarily autogamous, with transfer occurring within the same flower due to the fused structure that releases onto the stigma. Certain parthenocarpic variants develop seedless fruits without or fertilization, enhancing fruit set under adverse conditions like high temperatures or hormone treatments, and are bred for improved yield stability. To achieve hybrid vigor in breeding, of the is performed on the female parent flower before manual cross-, preventing selfing and enabling controlled hybridization for traits like disease resistance and larger fruits. In autogamous grasses such as (Triticum aestivum) and (), self-pollination within florets predominates, promoting uniform plant architecture and synchronized maturation that facilitate mechanical harvesting. This uniformity supports consistent yields across fields but increases risks of genetic bottlenecks, where reduced diversity heightens vulnerability to pests, diseases, and environmental stresses, as seen in modern cultivars derived from narrow founder populations. Agricultural practices for self-pollinating crops include hand-pollination techniques, such as vibrating flowers or using brushes to ensure pollen transfer in enclosed environments like greenhouses, where natural agents may be limited. Historical domestication of these crops, beginning around 10,000 years ago in regions like the Fertile Crescent for wheat and the Yangtze Valley for rice, favored self-pollinators because their tendency to breed true preserved selected traits like non-shattering seeds and larger grains. In controlled environments, self-pollination contributes to high seed set rates, often around 80% in crops like tomato, supporting efficient seed production without reliance on external pollinators.

Model Organisms

Arabidopsis thaliana serves as a premier model organism for studying self-pollination due to its fully autogamous reproductive strategy, where flowers self-pollinate before opening, resulting in an outcrossing rate of less than 0.3%. This trait facilitates rapid generation turnover in laboratory settings, typically completing a life cycle in 6-8 weeks, making it ideal for genetic analyses. The species' genome was the first plant genome fully sequenced in 2000, spanning approximately 135 million base pairs across five chromosomes, which has enabled extensive functional genomics research, including on flowering time regulation. Key genes such as FLOWERING LOCUS T (FT), which promotes the transition to reproductive phase under long-day conditions, have been dissected using Arabidopsis to understand how selfing integrates with developmental timing in autogamous plants. Capsella rubella, a close relative in the family, exemplifies a recent evolutionary shift to self-pollination, serving as a model for investigating the genetic basis of transitions. This annual herb underwent a switch from to predominant selfing approximately 30,000 to 50,000 years ago, coinciding with the loss of alleles at the S-locus, which prevented self-fertilization in its progenitor Capsella grandiflora. Genomic analyses reveal fixation of self-compatible mutations, such as deletions in SRK and SCR genes, leading to reduced and accelerated fixation compared to outcrossing relatives. This system has been instrumental in tracing the molecular underpinnings of selfing syndromes, including floral morphology changes that favor . In research applications, these model organisms support advanced genetic tools like (QTL) mapping to identify genomic regions controlling selfing rates and associated traits. For instance, QTL studies in Capsella have pinpointed loci influencing size reduction and nectar guide loss, adaptations that enhance self-pollination efficiency. CRISPR-Cas9 editing has been employed to manipulate mating-related genes, such as restoring self-incompatibility by targeting S-locus components or disrupting downstream signaling in , allowing precise dissection of reproductive barriers. A key finding from such studies is that selfing in these models accelerates propagation by minimizing the need for manual cross-pollination, enabling high-throughput experiments and fixed genetic backgrounds for trait analysis.

Specialized Cases

In certain orchid genera, cleistogamy manifests as a rare and derived form of self-pollination, enabling reproduction in pollinator-scarce or isolated habitats. The mycoheterotrophic genus Gastrodia includes multiple species with complete cleistogamy, such as G. kuroshimensis and G. takeshimensis, where flowers remain permanently closed, preventing opening and ensuring autonomous self-fertilization. This adaptation involves morphological modifications like the loss of the rostellum—a barrier typically separating pollinia from the stigma—allowing direct contact and pollen transfer within the flower. Transcriptomic studies reveal that cleistogamy in these species arises from heterochronic shifts, prolonging a juvenile developmental state and altering gene expression to converge on selfing without pollinator mediation. Similarly, in Dendrobium wangliangii, a lithophytic from dry-hot valleys in , , cleistogamous flowers predominate under water-deficit stress, with pollinia sliding from the anther cap directly into the stigmatic cavity to achieve at fruit-set rates up to 65%. The compact pollinia structure, unique to , facilitates this efficient selfing mechanism, particularly in fragmented populations where is unreliable due to isolation. Another specialized example occurs in the ginger family (), where Caulokaempferia coenobialis exhibits delayed self-pollination as an to persistently shady, humid microhabitats. This rhizomatous herb forms dense clonal populations on steep limestone cliffs in southern China's monsoon forests, where light levels are low and humidity exceeds 97%. Its bright yellow, ground-parallel flowers, measuring about 3 cm long, open briefly but rely on a novel sliding mechanism: anthers dehisce around 0600 hours, releasing in oily drops that form threads and migrate approximately 3 mm along the style to the stigma by late afternoon or the following morning. This autonomous process, the highest recorded level of self-compatibility in , ensures reproductive success in niches with limited access, contrasting with the bird- or insect-mediated typical of the family. Self-pollination also characterizes certain in extreme niches, such as carnivorous and aquatic species, where it promotes amid environmental constraints. Many carnivorous autonomously self-pollinate to balance the dual role of as both prey and pollinators, mitigating the pollinator-prey conflict that could otherwise limit seed set. Aquatic carnivores like bladderworts in the genus exemplify this, with species such as U. praeterita and U. babui employing delayed selfing in habitats; flowers initially permit insect visitation for but trigger autonomous pollen transfer if unpollinated, yielding high fruit-set rates (around 65%) and ensuring reproduction in geographically isolated, pollinator-poor ponds. This strategy enhances by reducing interspecific in sympatric communities, while providing assurance against mate or pollinator scarcity in ephemeral aquatic environments. These cases illustrate evolutionary transitions from ancestral to self-pollination, driven by selective pressures in isolated or unstable habitats. In orchids like Gastrodia, such shifts have occurred independently multiple times, with molecular dating placing origins in the Pleistocene (e.g., 1.01 Ma for G. kuroshimensis), though broader angiosperm breeding system diversification, including self-compatibility, aligns with floral evolution as evidenced by fossil records of structural changes in reproductive organs. Fossil-calibrated phylogenies further suggest that environmental shifts, such as cooling climates and , facilitated repeated selfing transitions across lineages, enhancing survival in niche environments without relying on biotic vectors.

Genetic Implications

Short-Term Effects

Self-pollination induces a rapid surge in homozygosity within the F1 , as gametes from the same parent combine, resulting in approximately 50% of offspring becoming homozygous for each parental at heterozygous loci. This process fixes alleles more quickly than , reducing heterozygosity and exposing to selection in subsequent generations. In finite populations, the inbreeding coefficient FF, defined as the probability that two alleles at a locus are identical by descent, increases by approximately 12Ne\frac{1}{2N_e} per due to the combined effects of selfing and on allele identity, where NeN_e is the . Physiologically, self-pollination affects seed quality by promoting genetic uniformity, though overall seedling vigor is typically reduced due to . This lower vigor manifests as slower growth, weaker establishment, and higher susceptibility to environmental stresses in early development. Concurrently, the increased homozygosity unmasks recessive traits, including deleterious alleles that were previously hidden in heterozygous states, potentially compromising individual fitness through the expression of harmful phenotypes. In populations, self-pollination restricts by limiting dispersal to within individuals or nearby relatives, thereby enhancing the potential for local adaptations to specific environmental conditions through reduced homogenization of frequencies across habitats. studies, including allozyme and analyses, have documented selfing rates of 50–100% in various wild plant populations, such as and , underscoring the role of selfing in shaping immediate population genetic structure.

Long-Term Benefits of Meiosis

Self-pollination increases homozygosity across the , exposing recessive deleterious mutations to and facilitating their purging from populations over multiple generations. This process mitigates the accumulation of associated with , as homozygous individuals expressing harmful recessive alleles experience reduced fitness and are selected against. Theoretical models indicate that such purging can lead to fitness recovery in selfing populations. Meiosis remains essential in self-pollinating , as it enables recombination during formation, thereby generating novel genetic combinations that counteract the homogenizing effects of repeated self-fertilization. This recombination introduces variation at the level, allowing to changing conditions despite elevated homozygosity. The genetic load from recessive deleterious in selfers can be approximated by the equation L=q2L = q^2, where qq represents the frequency of the deleterious , reflecting the proportion of homozygous individuals affected under complete selfing. From an evolutionary perspective, the transition to self-pollination is widely regarded as a derived trait in angiosperms, evolving from outcrossing ancestors and conferring advantages in stable, predictable environments where pollinator reliability is low. Stebbins' foundational model posits that selfing promotes population uniformity and reproductive assurance in such habitats, reducing reliance on external vectors. Contemporary studies from the reinforce this, showing that selfing lineages exhibit enhanced colonization success in uniform conditions, with genomic signatures indicating repeated independent origins of self-compatibility. Recent genomic investigations provide empirical support for meiosis-mediated benefits in selfers, revealing reduced abundance of transposable elements (TEs) in self-pollinating species compared to relatives. For instance, , a predominant selfer, displays a marked decline in TE content relative to its relative Arabidopsis lyrata, attributed to the exposure and subsequent selection against TE-induced mutations under homozygosity. This TE reduction alleviates mutational burdens, enhancing long-term genomic stability and fitness.

References

  1. https://pmc.ncbi.nlm.nih.gov/articles/PMC34381/
  2. https://faculty.csbsju.edu/ssaupe/biol116/Botany/plant-repro-lec.htm
  3. https://pmc.ncbi.nlm.nih.gov/articles/PMC3652455/
  4. https://byjus.com/biology/difference-between-cross-pollination-and-self-pollination/
  5. https://oertx.highered.texas.gov/courseware/lesson/1777/overview
  6. https://www.ncbi.nlm.nih.gov/books/NBK9991/
  7. https://ib.berkeley.edu/courses/ib168/LectureHandouts/Lecture15.pdf
  8. https://www.bio.fsu.edu/~winn/bsc3402L/Chapter_Three.pdf
  9. https://www.oed.com/dictionary/self-pollination_n
  10. https://www.etymonline.com/word/autogamy
  11. https://pmc.ncbi.nlm.nih.gov/articles/PMC548810/
  12. https://nph.onlinelibrary.wiley.com/doi/10.1111/nph.12874
  13. https://www.researchgate.net/publication/51201585_Self-pollination_in_island_and_mainland_populations_of_the_introduced_hummingbird-pollinated_plant_Nicotiana_glauca_Solanaceae
  14. https://www.mdpi.com/2223-7747/14/10/1410
  15. https://bsapubs.onlinelibrary.wiley.com/doi/10.3732/ajb.1000223
  16. https://pmc.ncbi.nlm.nih.gov/articles/PMC12114905/
  17. https://academic.oup.com/evolut/article/59/4/786/6756961
  18. https://www.britannica.com/plant/Poaceae/Characteristic-morphological-features
  19. https://www.cabidigitallibrary.org/doi/pdf/10.5555/20083249544
  20. https://bsapubs.onlinelibrary.wiley.com/doi/10.3732/ajb.91.5.672
  21. https://www.asianscientist.com/2025/06/environment/on-the-evolution-of-orchids-that-never-bloom/
  22. https://royalsocietypublishing.org/doi/10.1098/rspb.2013.0133
  23. https://academic.oup.com/book/5359/chapter/148152065
  24. https://microbenotes.com/pollination/
  25. http://www.eagri.org/eagri50/GBPR211/lec04.pdf
  26. https://www.researchgate.net/publication/334608278_Early_Maturity_Small_Flowers_and_Autogamy_A_Developmental_Connection
  27. https://www.journals.uchicago.edu/doi/pdfplus/10.1086/297040
  28. https://www.pollinationecology.org/index.php/jpe/article/download/741/410
  29. https://bsapubs.onlinelibrary.wiley.com/doi/10.3732/ajb.90.12.1746
  30. https://link.springer.com/article/10.1007/BF00317407
  31. https://pmc.ncbi.nlm.nih.gov/articles/PMC9399832/
  32. https://open.lib.umn.edu/horticulture/chapter/7-2-flower-morphology/
  33. https://pmc.ncbi.nlm.nih.gov/articles/PMC5751043/
  34. https://bioone.org/journals/the-botanical-review/volume-73/issue-1/0006-8101_2007_73_1_TCBSAR_2.0.CO_2/The-Cleistogamous-Breeding-System--A-Review-of-Its-Frequency/10.1663/0006-8101%282007%2973%5B1:TCBSAR%5D2.0.CO%3B2.short
  35. https://pmc.ncbi.nlm.nih.gov/articles/PMC3829907/
  36. https://www.journals.uchicago.edu/doi/pdfplus/10.1086/337056
  37. https://www.researchgate.net/publication/225503104_The_Cleistogamous_Breeding_System_A_Review_of_Its_Frequency_Evolution_and_Ecology_in_Angiosperms
  38. https://btny.purdue.edu/labs/oakley/ewExternalFiles/Oakleyetal_2007_ARES.pdf
  39. https://pmc.ncbi.nlm.nih.gov/articles/PMC3278291/
  40. https://pmc.ncbi.nlm.nih.gov/articles/PMC2701783/
  41. https://bmcecol.biomedcentral.com/articles/10.1186/1472-6785-5-2
  42. https://www.nature.com/articles/ncomms13313
  43. https://www.mdpi.com/2073-4395/10/3/349
  44. https://pmc.ncbi.nlm.nih.gov/articles/PMC6927913/
  45. https://doi.org/10.1098/rspb.2013.0133
  46. https://pmc.ncbi.nlm.nih.gov/articles/PMC3170157/
  47. https://www.pnas.org/doi/10.1073/pnas.0403809101
  48. https://www.ecologyandsociety.org/vol6/iss1/art16/
  49. https://bsapubs.onlinelibrary.wiley.com/doi/10.1002/ajb2.1045
  50. https://pmc.ncbi.nlm.nih.gov/articles/PMC3278284/
  51. https://www.nature.com/articles/s41467-021-24267-6
  52. https://www.nature.com/articles/hdy199018.pdf
  53. https://www.pnas.org/doi/pdf/10.1073/pnas.81.16.5258
  54. https://seedalliance.org/publications/tomato-seed-production-guide/
  55. https://www.nature.com/articles/s41598-017-00501-4
  56. https://tgrc.ucdavis.edu/pollinating
  57. https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/self-pollination
  58. https://pmc.ncbi.nlm.nih.gov/articles/PMC6304682/
  59. https://agritech.tnau.ac.in/crop_improvement/crop_imprv_selfcross.html
  60. https://www.fao.org/4/i1070e/i1070e01.pdf
  61. https://academic.oup.com/aobpla/article/13/4/plab046/6323247
  62. https://elifesciences.org/articles/06100
  63. https://nph.onlinelibrary.wiley.com/doi/10.1111/nph.18495
  64. https://pmc.ncbi.nlm.nih.gov/articles/PMC6875582/
  65. https://www.researchgate.net/publication/228496873_Self-Pollination_by_Sliding_Pollen_in_Caulokaempferia_coenobialis_Zingiberaceae
  66. https://academic.oup.com/aob/article/102/3/305/228692
  67. https://pubmed.ncbi.nlm.nih.gov/22188434/
  68. https://pubmed.ncbi.nlm.nih.gov/29460199/
  69. https://www.pnas.org/doi/10.1073/pnas.97.13.7030
  70. https://www.ucl.ac.uk/~ucbhdjm/courses/b242/InbrDrift/InbrDrift.html
  71. https://iastate.pressbooks.pub/cropgenetics/chapter/inbreeding-and-heterosis-2/
  72. https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2021.619154/full
  73. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0014473
  74. https://www.jstor.org/stable/56203
  75. https://royalsocietypublishing.org/doi/10.1098/rstb.2020.0510
  76. https://mobilednajournal.biomedcentral.com/articles/10.1186/1759-8753-3-2
  77. https://pmc.ncbi.nlm.nih.gov/articles/PMC1461736/
Add your contribution
Related Hubs
User Avatar
No comments yet.