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Self-pollination

Self-pollination is the transfer of pollen from the anther to the stigma within the same flower (autogamy) or between flowers on the same plant (geitonogamy), leading to self-fertilization in flowering plants.^[1] This process occurs primarily in hermaphroditic flowers where male and female reproductive organs mature simultaneously, allowing pollen to contact the stigma without external agents, though mechanisms like self-incompatibility systems can prevent it in some species to promote outcrossing.^[2]^[1] Self-pollination has evolved repeatedly from outcrossing ancestors, often providing reproductive assurance in environments with unreliable pollinators, but it is counterbalanced by evolutionary traits favoring genetic diversity.^[1] Key advantages include reduced dependence on pollinators, minimal pollen wastage, and preservation of desirable traits across generations, enabling reliable seed production in stable habitats.^[2]^[1] However, it carries significant disadvantages, such as decreased genetic variation that limits adaptation to diseases or environmental changes, and increased risk of inbreeding depression, where selfed offspring exhibit reduced fitness due to homozygous deleterious alleles.^[1] These trade-offs influence the prevalence of self-pollination in approximately 10-15% of angiosperm species, with higher rates in isolated or colonizing populations.^[1]^[3] Examples of self-pollinating plants include many crops like wheat, rice, and peas, where the trait supports uniform yields but underscores the need for breeding programs to introduce diversity.^[4] In evolutionary terms, selfing offers a transmission advantage for self-compatibility alleles but can lead to long-term lineage decline without occasional outcrossing.^[1]

Fundamentals

Definition

Self-pollination is a reproductive process in flowering plants 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 plant, enabling fertilization without reliance on external agents such as wind or pollinators.^[5]^[6] This mechanism contrasts with cross-pollination, or allogamy, which requires pollen transfer between genetically distinct plants to achieve fertilization and promotes genetic diversity in offspring.^[7] In angiosperms, self-pollination represents a form of sexual reproduction that can occur autonomously within the flower structure, contributing to seed production in environments where pollinators are scarce.^[8] 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.^[8]^[7] 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").^[9]^[10] 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.^[11]

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.^[12]^[3] 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.^[13]^[14] Ecologically, self-pollination is particularly favored in habitats characterized by low pollinator density, including high-altitude regions, deserts, and post-disturbance sites where resources are ephemeral or fragmented.^[15]^[16]^[17] In such conditions, the strategy ensures seed production despite unreliable biotic pollination services, as seen in desert flora adapting to sparse insect 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 Poaceae (grasses), where species like wheat (Triticum aestivum) and rice (Oryza sativa) rely on it through cleistogamous or enclosed inflorescences.^[18] In Fabaceae (legumes), it prevails in many cultivated forms such as peas (Pisum sativum), often via bud pollination before flowers open.^[19] Similarly, Solanaceae (nightshades) features self-pollination in crops like tomatoes (Solanum lycopersicum), supported by anther-stigma proximity.^[20] Conversely, it is rare in families with elaborate, showy flowers, such as Orchidaceae, where most species depend on specialized pollinator interactions unless rare cleistogamous adaptations occur.^[21] The occurrence of self-pollination has arisen through multiple independent evolutionary origins across plant lineages, frequently associated with the colonization of novel or challenging habitats that impose selective pressures for reproductive autonomy.^[3]^[22] This repeated transition underscores its adaptive value in diverse ecosystems, from continental expansions to insular invasions.

Mechanisms

Autogamy

Autogamy is the transfer of pollen 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 gravity, where pollen grains fall onto the stigma.^[23]^[24] 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.^[15] Genetically, autogamy results in an immediate increase in homozygosity among progeny, as the offspring inherit identical alleles from a single parental gamete fusion, accelerating the fixation of homozygous genotypes across generations. This contrasts with outcrossing by promoting inbreeding and reducing heterozygosity from the outset.^[25] Autogamy prevails as the dominant mode of self-pollination, especially in small, inconspicuous flowers that lack elaborate displays or nectar rewards to attract pollinators, thereby conserving resources while ensuring seed production. These floral traits correlate with faster developmental timing and higher selfing efficiency, as observed in numerous annual and perennial species adapted to stable or resource-limited habitats.^[26]

Geitonogamy and Cleistogamy

Geitonogamy refers to the transfer of pollen from the anther of one flower to the stigma of another flower on the same plant, a process that results in self-fertilization despite involving inter-flower movement similar to cross-pollination mechanisms.^[27] This form of self-pollination is commonly mediated by pollinators, such as insects, or abiotic agents like wind, particularly in plants with large inflorescences where sequential flower visits increase the likelihood of within-plant pollen transfer.^[28] Genetically, geitonogamy is equivalent to autogamy as it unites gametes from the same individual, but it can create an illusion of outcrossing at the population level since pollen dispersal mimics xenogamy; however, it often leads to pollen wastage by diverting resources that could facilitate gene flow between plants.^[27] In species like Asclepias syriaca (common milkweed), high rates of geitonogamy mediated by pollinators have been shown to significantly reduce fruit set due to resource allocation to aborted selfed seeds.^[29] Unlike autogamy, which occurs within a single flower, geitonogamy 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-pollen deposition on stigmas.^[30] For instance, in Ipomopsis aggregata, flowers on larger plants receive proportionally more self-pollen via geitonogamy, leading to higher selfing rates compared to smaller plants.^[30] This mechanism can impose costs in self-compatible species by increasing competition between self- and outcross-pollen on stigmas, potentially reducing overall reproductive success.^[31] Cleistogamy involves self-pollination and fertilization entirely within unopened, bud-like flowers that remain closed throughout their development, ensuring autonomous reproduction without reliance on external pollinators.^[32] These cleistogamous flowers are typically reduced in size, with fused or absent petals, minimal nectar production, and internal anther dehiscence that deposits pollen directly onto the stigma, often facilitated by mechanical pressure from elongating filaments.^[8] This adaptation is energy-efficient, as it minimizes investment in floral attractants and structures for pollinator access, often producing smaller seeds but with comparable or higher seed set efficiency due to guaranteed pollination.^[33] Cleistogamy has evolved independently in approximately 693 species across 50 families (as of 2007), providing reproductive assurance in environments with unreliable pollinators or sparse populations.^[34] In many cleistogamous species, plants exhibit dimorphism by producing both cleistogamous flowers for obligatory selfing and larger chasmogamous (open) flowers capable of outcrossing, allowing flexible resource allocation based on environmental cues such as nutrient availability or stress.^[35] 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 mating.^[36] Similarly, the legume Arachis hypogaea (peanut) primarily reproduces via cleistogamous flowers that develop below ground after peg elongation, ensuring seed production in nutrient-poor soils.^[37] 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.^[38] 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.^[33] 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.^[27]

Evolutionary Aspects

Advantages

Self-pollination provides reproductive assurance by enabling plants to achieve fertilization and seed production independently of external pollinators or mates, which is particularly beneficial in environments where pollinator activity is limited or unreliable.^[39] This mechanism ensures higher seed set compared to outcrossing in such conditions, with studies demonstrating that autonomous selfing can increase seed production by an average of 84% in alpine populations facing pollinator limitation.^[40] For instance, in alpine environments with scarce pollinators, autonomous selfing has been shown to account for the majority of fruit and seed set, preventing reproductive failure.^[40] In terms of efficiency, self-pollinating plants allocate fewer resources to producing elaborate floral attractants such as nectar, scents, or large displays, allowing them to redirect energy toward growth, seed development, and survival.^[3] This reduced investment in pollination structures often results in smaller, less conspicuous flowers, which lowers overall reproductive costs and enables faster generation times, facilitating quicker maturation and seed dispersal in resource-limited settings.^[41] Self-pollination supports population dynamics 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.^[42] This capability increases the success of founder events and colonization, particularly for species invading disturbed or remote areas, where outcrossing populations might fail due to mate scarcity.^[3] Field studies provide empirical evidence of higher fitness for self-pollinating plants during droughts, where pollinator decline exacerbates pollen limitation, but selfing maintains seed output and plant survival.^[43] For example, in water-stressed conditions, self-compatible species exhibit greater reproductive success through assured seed set, enabling drought escape via rapid life cycles and reduced dependence on fluctuating pollinator services.^[44]

Disadvantages

Self-pollination often results in inbreeding depression, characterized by reduced heterozygosity and the expression of deleterious recessive alleles, leading to lower fitness in offspring compared to outcrossed progeny.^[45] In plants, meta-analyses indicate that inbreeding depression causes fitness reductions across various traits, though this can vary widely depending on the species and environmental conditions. Over successive generations, selfing accelerates the accumulation of deleterious alleles due to decreased effective population size and weakened purifying selection, further exacerbating fitness declines.^[45] 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.^[46] 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 genetic diversity within populations, limiting their ability to adapt to environmental changes like pathogens, climate shifts, or habitat alterations.^[45] Low heterozygosity impairs evolutionary potential, making selfing populations more susceptible to local extinctions during stressors that favor novel genetic combinations.^[47] Historical examples illustrate these risks; similarly, modeling studies on threatened species demonstrate that inbreeding from self-fertilization can shorten population persistence times by 25-30%, contributing to higher overall extinction probabilities in small, isolated groups.^[48]

Mixed Mating Systems

Mixed mating systems in plants 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 plants are not fully self-incompatible but exhibit reduced success in self-fertilization compared to outcrossing, allowing flexibility in reproductive strategies.^[42] Selfing rates in such systems can be modulated by environmental cues, such as pollinator availability or stress conditions, or by genetic factors that influence pollen-pistil interactions.^[49] 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 genetic diversity gained from outcrossing, which mitigates inbreeding depression.^[42] This equilibrium is particularly evident in colonizing species, as described by Baker's Law, which posits that self-compatible plants are more likely to successfully establish in new habitats due to their ability to reproduce from single individuals.^[50] Empirical studies across global floras confirm that species with higher self-compatibility indices exhibit greater naturalization success, supporting the role of mixed mating in invasion biology.^[42] Mechanisms regulating mixed mating include delayed selfing, where flowers first facilitate outcrossing via pollinators before autonomously self-pollinating if unvisited, often through architectural features like stigma retraction or pollen shedding.^[49] Many plants 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.^[33] At the genetic level, loci such as the S-locus inhibitor (Sli) gene promote partial self-compatibility by overriding self-incompatibility responses, allowing controlled self-fertilization in otherwise outcrossing lineages.^[51] In population genetics, outcrossing rates in mixed mating 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.^[52] These markers help quantify the proportion of selfed versus outcrossed offspring, demonstrating how ecological factors like pollinator density influence mating dynamics without requiring full genomic sequencing.^[53]

Examples

Crop Plants

The tomato (Solanum lycopersicum) is primarily autogamous, with pollen transfer occurring within the same flower due to the fused anther cone structure that releases pollen onto the stigma.^[54] Certain parthenocarpic variants develop seedless fruits without pollination or fertilization, enhancing fruit set under adverse conditions like high temperatures or hormone treatments, and are bred for improved yield stability.^[55] To achieve hybrid vigor in tomato breeding, emasculation of the anther cone is performed on the female parent flower before manual cross-pollination, preventing selfing and enabling controlled hybridization for traits like disease resistance and larger fruits.^[56] In autogamous grasses such as wheat (Triticum aestivum) and rice (Oryza sativa), self-pollination within florets predominates, promoting uniform plant architecture and synchronized maturation that facilitate mechanical harvesting.^[57] 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.^[58] 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.^[59] 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.^[60] 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.^[61]

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 Brassicaceae family, exemplifies a recent evolutionary shift to self-pollination, serving as a model for investigating the genetic basis of mating system transitions. This annual herb underwent a switch from outcrossing to predominant selfing approximately 30,000 to 50,000 years ago, coinciding with the loss of self-incompatibility 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 genetic diversity and accelerated allele fixation compared to outcrossing relatives. This system has been instrumental in tracing the molecular underpinnings of selfing syndromes, including floral morphology changes that favor autogamy. In research applications, these model organisms support advanced genetic tools like quantitative trait locus (QTL) mapping to identify genomic regions controlling selfing rates and associated traits. For instance, QTL studies in Capsella have pinpointed loci influencing petal 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 Arabidopsis, allowing precise dissection of reproductive barriers. A key finding from such studies is that selfing in these models accelerates laboratory propagation by minimizing the need for manual cross-pollination, enabling high-throughput experiments and fixed genetic backgrounds for trait analysis.^[62]

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.^[63] 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 MADS-box gene expression to converge on selfing without pollinator mediation.^[63] Similarly, in Dendrobium wangliangii, a lithophytic orchid from dry-hot valleys in Yunnan, China, cleistogamous flowers predominate under water-deficit stress, with pollinia sliding from the anther cap directly into the stigmatic cavity to achieve autogamy at fruit-set rates up to 65%.^[64] The compact pollinia structure, unique to orchids, facilitates this efficient selfing mechanism, particularly in fragmented populations where outcrossing is unreliable due to isolation.^[64] Another specialized example occurs in the ginger family (Zingiberaceae), where Caulokaempferia coenobialis exhibits delayed self-pollination as an adaptation 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%.^[65] Its bright yellow, ground-parallel flowers, measuring about 3 cm long, open briefly but rely on a novel sliding pollen mechanism: anthers dehisce around 0600 hours, releasing pollen in oily drops that form threads and migrate approximately 3 mm along the style to the stigma by late afternoon or the following morning.^[65] This autonomous process, the highest recorded level of self-compatibility in Zingiberaceae, ensures reproductive success in understory niches with limited pollinator access, contrasting with the bird- or insect-mediated outcrossing typical of the family.^[66] Self-pollination also characterizes certain plants in extreme niches, such as carnivorous and aquatic species, where it promotes reproductive isolation amid environmental constraints. Many carnivorous plants autonomously self-pollinate to balance the dual role of insects as both prey and pollinators, mitigating the pollinator-prey conflict that could otherwise limit seed set.^[67] Aquatic carnivores like bladderworts in the genus Utricularia exemplify this, with species such as U. praeterita and U. babui employing delayed selfing in wetland habitats; flowers initially permit insect visitation for outcrossing but trigger autonomous pollen transfer if unpollinated, yielding high fruit-set rates (around 65%) and ensuring reproduction in geographically isolated, pollinator-poor ponds.^[68] This strategy enhances reproductive isolation by reducing interspecific gene flow in sympatric communities, while providing assurance against mate or pollinator scarcity in ephemeral aquatic environments.^[68] These cases illustrate evolutionary transitions from ancestral outcrossing 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 cleistogamy origins in the Pleistocene (e.g., 1.01 Ma for G. kuroshimensis), though broader angiosperm breeding system diversification, including self-compatibility, aligns with Miocene floral evolution as evidenced by fossil records of structural changes in reproductive organs.^[63]^[69] Fossil-calibrated phylogenies further suggest that Miocene environmental shifts, such as cooling climates and habitat fragmentation, facilitated repeated selfing transitions across lineages, enhancing survival in niche environments without relying on biotic vectors.^[69]

Genetic Implications

Short-Term Effects

Self-pollination induces a rapid surge in homozygosity within the F1 generation, as gametes from the same parent combine, resulting in approximately 50% of offspring becoming homozygous for each parental allele at heterozygous loci. This process fixes alleles more quickly than outcrossing, reducing heterozygosity and exposing genetic variation to selection in subsequent generations. In finite populations, the inbreeding coefficient F, defined as the probability that two alleles at a locus are identical by descent, increases by approximately \frac{1}{2N_e} per generation due to the combined effects of selfing and genetic drift on allele identity, where N_e is the effective population size.^[70] Physiologically, self-pollination affects seed quality by promoting genetic uniformity, though overall seedling vigor is typically reduced due to inbreeding depression. 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.^[71] In populations, self-pollination restricts gene flow by limiting pollen dispersal to within individuals or nearby relatives, thereby enhancing the potential for local adaptations to specific environmental conditions through reduced homogenization of allele frequencies across habitats. Molecular marker studies, including allozyme and microsatellite analyses, have documented selfing rates of 50–100% in various wild plant populations, such as Arabidopsis thaliana and Medicago truncatula, underscoring the role of selfing in shaping immediate population genetic structure.^[22]^[72]

Long-Term Benefits of Meiosis

Self-pollination increases homozygosity across the genome, exposing recessive deleterious mutations to natural selection and facilitating their purging from populations over multiple generations. This process mitigates the accumulation of genetic load associated with inbreeding, 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.^[73] Meiosis remains essential in self-pollinating species, as it enables recombination during gamete formation, thereby generating novel genetic combinations that counteract the homogenizing effects of repeated self-fertilization. This recombination introduces variation at the population level, allowing adaptation to changing conditions despite elevated homozygosity. The genetic load from recessive deleterious alleles in selfers can be approximated by the equation L = q^2, where q represents the frequency of the deleterious allele, reflecting the proportion of homozygous individuals affected under complete selfing.^[22] 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.^[74] Contemporary studies from the 2020s reinforce this, showing that selfing lineages exhibit enhanced colonization success in uniform conditions, with genomic signatures indicating repeated independent origins of self-compatibility.^[75] 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 outcrossing relatives. For instance, Arabidopsis thaliana, a predominant selfer, displays a marked decline in TE content relative to its outcrossing 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.^[76]^[77]

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INBREEDING AND GENETIC DRIFT
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[PDF] Self-Pollination Effects on Seed and Seedling Traits in Noble Fir
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Theoretical models predict that the mating system should be an important factor driving the dynamics of transposable elements in natural populations due to ...