Autogamy, or self-fertilization, refers to the fusion of two gametes that come from one individual. Autogamy is predominantly observed in the form of self- pollination, a reproductive mechanism employed by many flowering plants. However, species of protists have also been observed using autogamy as a means of reproduction. Flowering plants engage in autogamy regularly, while the protists that engage in autogamy only do so in stressful environments.
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The relation of autogamy to senescence and rejuvenescence in Paramecium aurelia.
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The evolutionary shift from outcrossing to self-fertilization is one of the most frequent evolutionary transitions in plants. About 10-15% of flowering plants are predominantly self-fertilizing. Since autogamy in flowering plants and autogamy in unicellular species is fundamentally different, and plants and protists are not related, it is likely that both instances evolved separately. In flowering plants, it is believed that autogamy evolved one million years ago.
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Research shows that Paramecium aurelia undergo autogamy synchronously with other individuals of the same species.
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Similar to Paramecium aurelia, the parasitic ciliate Tetrahymena rostrata has also been shown to engage in meiosis, autogamy and development of new macronuclei when placed under nutritional stress. Due to the degeneration and remodeling of genetic information that occurs in autogamy, genetic variability arises and possibly increases an offspring’s chances of survival in stressful environments.
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Cleistogamous flowers are produced along with chasmogamous flowers on the same plant resulting in a mixed mating system that ensures reproductive success through autogamy.
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However, due to the little overall genetic variation that arises in progeny, it is not fully understood how autogamy has been maintained in the tree of life.
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It is possible that the nutrition deprived state of the parent cells before autogamy created a barrier for producing offspring that could thrive in those same stressful environments.
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Similar to delayed selfing, fertilization via autogamy occurs when there is a lack of pollinators and has evolved as a form of reproductive assurance to ensure successful reproduction.
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The flowering period extends from July through October. The hermaphroditic flowers are either self-fertilized (autogamy) or pollinated by insects (entomogamy). The seeds are an achene that ripens in October.
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Cullenia exarillata is an outcrossing species, producing negligible fruit-set under geitonogamy and no fruit-set under autogamy. The seeds are mechanically dispersed (gravity) as well as by Lion-tailed Macaques over short distances.
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The odorless, nectar-less flowers do not rely on insect pollinators for pollination, rather setting seed well through self-pollination (autogamy). The black ovoid seed forms in a dehiscent capsule and is 1 to mm long.
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It has been found that xenogamy in this species leads to more fruits per flower and more seeds in each fruit compared to autogamy; this was reported to be true in both observational studies and controlled experiments.
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In flowering plants, autogamy has the disadvantage of producing low genetic diversity in the species that use it as the predominant mode of reproduction. This leaves those species particularly susceptible to pathogens and viruses that can harm it. In addition, the foraminiferans that use autogamy have shown to produce substantially smaller progeny as a result. This indicates that since it is generally an emergency survival mechanism for unicellular species, the mechanism does not have the nutritional resources that would be provided by the organism if it were undergoing binary fission.
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Synandra is a monotypic genusCantino, P. D. (1985). Facultative autogamy in Synandra hispidula (Labiatae). Castanea 50(2) 105-11. of flowering plants in the mint family containing the single species Synandra hispidula, which is known by the common name Guyandotte beauty.
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Finley, Harold E. "The conjugation of Vorticella microstoma." Transactions of the American Microscopical Society (1943): 97-121. In most ciliate groups, however, the cells separate after conjugation, and both form new macronuclei from their micronuclei. Conjugation and autogamy are always followed by fission.
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It flowers from June until September. The flowers are pollinated by insects (usually bees, wasps and butterflies) (entomogamy) and are hermaphrodite (self fertilization or autogamy). The fruits are hairy cylindrical achenes about 7 to 8 mm long. They ripen from September through October.
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The flowering period extends from May to July in the Northern Hemisphere. The flowers are either self- fertilized (autogamy) or pollinated by insects such as bees and butterflies (entomogamy). The seeds ripen from August to September and are dispersed by gravity alone (barochory).
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Such a benefit may have been sufficient to allow the long-term persistence of meioses even when followed by self- fertilization. A physical mechanism for self-pollination in A. thaliana is through pre-anthesis autogamy, such that fertilisation takes place largely before flower opening.
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Individual crowns are treated as, "independent mitotic mutation-accumulation lines" and so the appearance of deleterious somatic mutations in the autogamous crosses will be heterozygous or homozygous at the same locus (~25% homozygous) and the appearance of deleterious somatic mutations in the geitonogamous crosses will be heterozygous. The autogamy depression can be calculated through the simple equation AD = 1-(wa/wg), where AD is the Autogamy Depression, wa is the fitness of the autogamous progeny and wg is the fitness of the geitonogamous progeny. When the fitnesses are equal the AD is 0. The difference can be calculated by the equation, D = wg-wa.
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Monocots have mechanisms to promote or suppress cross-fertilization (allogamy) and self- fertilization (autogamy or geitonogamy). The pollination syndromes of monocots can be quite distinct; they include having flower parts in multiples of three, adaptations to pollination by water (hydrogamy), and pollination by sexual deception in orchids.
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Most strains are haploid, mating very rarely and diploidize transiently by somatogamous autogamy (i.e. fusion of two cells but excluding their nuclei). Sexual reproduction proceeds via heterogamous conjugation (i.e. the conjugation of two cells of different form or size) leading to short diplophase followed by meiosis and ascospore formation.
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Allogamy, which is also known as cross-fertilisation, refers to the fertilisation of an egg cell from one individual with the male gamete of another. Autogamy which is also known as self-fertilisation, occurs in such hermaphroditic organisms as plants and flatworms; therein, two gametes from one individual fuse.
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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.
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Under unfavourable conditions, some species will form a cyst. This is often the product of autogamy, in which case the cysts produced are zygotes. Cells undergoing this process withdraw their axopodia, adhere to the substrate, and take on an opaque and grayish appearance. This cyst then divides until only uninucleate cells remain.
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Autogamy has been observed in several species of onion orchid. In some cases, the pollen grains fall onto the stigma and germinate but in others, including in some populations of M. parvifolia, if the flowers have not been cross-pollinated, the stigma grows upwards until it contacts the pollinia, so that seed is always produced.
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These hairs, along with the more or less oblong form of the inflorescence, are the inspiration for the common name. Pollination is carried out by bees, or via autogamy, since the plant is hermaphroditic, and the flowering season is from mid-spring to late summer. The fruit is a small pod containing a single seed.
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Owing to the prenathesis cleistogamy, a form of autogamy (self-pollination), the known population of L. schismatica lacks genetic variability and has a high incidence of homozygosity.Coello, G., Escalante, A., and Soberon, J. (1993). Lack of genetic variation in Lacandonia schismatica in its only known locality. Annals of the Missouri Botanical Garden, 80(4): 898-901.
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If the protists reproduce asexually, they do so through binary fission, multiple fission, budding, and fragmentation. If the protists reproduce sexually, they do so through a syngamy process where there is a fusion of the gametes. If this occurs in an individual it is recognized as autogamy. If this occurs between individuals, it is known as conjugation.
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Allogamy or cross-fertilization is the fertilization of an ovum from one individual with the spermatozoa of another. By contrast, autogamy is the term used for self-fertilization. In humans, the fertilization event is an instance of allogamy. Self-fertilization occurs in hermaphroditic organisms where the two gametes fused in fertilization come from the same individual.
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This indicates that insect-mediated pollination is important in keeping fruit- and seed-set high, and individual fecundity high. Pollinators appear to be the limiting factor in fruit and seed production. Because aboveground populations fluctuate wildly, autogamy helps ensure fecundity and may be a key life history trait. Germination in W. carteri occurs in late winter through early spring (January–March).
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Habit Experiments have demonstrated that Warea carteri is self-pollinating, autogamous, and self-compatible. Autogamy and selfcompatibility allow isolated or sparsely distributed individuals to reproduce. Natural levels of fruit- and seed-set are quite high, with a fruit- set of 62 percent, and seed-set of 50 percent. Self-pollinated flowers showed significantly lower fruit- and seed-set, 41 percent fruit-set and 28 percent seed-set.
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Outcrossing, cross-fertilization or allogamy, in which offspring are formed by the fusion of the gametes of two different plants, is the most common mode of reproduction among higher plants. About 55% of higher plant species reproduce in this way. An additional 7% are partially cross-fertilizing and partially self-fertilizing (autogamy). About 15% produce gametes but are principally self-fertilizing with significant out-crossing lacking.
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Mating may also lead to external fertilization, as seen in amphibians, fishes and plants. For the majority of species, mating is between two individuals of opposite sexes. However, for some hermaphroditic species, copulation is not required because the parent organism is capable of self-fertilization (autogamy); for example, banana slugs. The term mating is also applied to related processes in bacteria, archaea and viruses.
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Self- pollination is an example of autogamy that occurs in flowering plants. Self- pollination occurs when the sperm in the pollen from the stamen of a plant goes to the carpels of that same plant and fertilizes the egg cell present. Self-pollination can either be done completely autogamously or geitonogamously. In the former, the egg and sperm cells that united came from the same flower.
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This species blossoms usually from April to May, sometimes already in March. When the flowers open, the stamens move towards the centre and arrange in a conical structure, where the anthers at the tip surround the stigmas. This structure involves an efficient autogamy mechanism, that guarantees the self-fetilization.A. Guillen, E. Rico, E. Castroviejo Reproductive biology of the Iberian species of Potentilla (Rosaceae) This plant reproduces by seeds.
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The seedlings from one kernel can germinate at the same time or be spread over a year. The nut has four apertures in the endocarp each guarded by an oval door and each leading to a seed chamber. The Puriri is self-fertile with self-fertilization (autogamy) possible. Seed production in 12 samples ranged from 8% to 45% with usually only 1 or 2 live seeds in a fruit.
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As opposed to outcrossing or outbreeding, inbreeding is the process by which organisms with common descent come together to mate and eventually procreate. An archetype of inbreeding is self-pollination. When a plant has both anthers and a stigma, the process of inbreeding can occur. Another word for this self- fertilization is autogamy, which is when an anther releases pollen to attach to the stigma on the same plant.
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There are often observations of macronuclei and chromosomal fragments coexisting in Allogromia laticollaris. This is indicative of nuclear and chromosomal degeneration, a process similar to the subdivisions observed in Paramecium aurelia. Multiple generations of haploid Allogromia laticollaris individuals can exist before autogamy actually takes place. The autogamous behavior in Allogromia laticollaris has the added consequence of giving rise to daughter cells that are substantially smaller than those rising from binary fission.
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Aside from extreme circumstances, it is possible that this form of reproduction gives rise to a genotype in the offspring that will increase fitness in the environment. This is due to the nature of the genetic degeneration and remodeling intrinsic to autogamy in unicellular organisms. Thus, autogamous behavior may become advantageous to have if an individual wanted to ensure offspring viability and survival. This advantage also applies to flowering plants.
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Allogromia laticollaris is perhaps the best- studied foraminiferan amoeboid for autogamy. Allogromia laticollaris can alternate between sexual reproduction via cross-fertilization and asexual reproduction via binary fission. The details of the life cycle of Allogromia laticollaris are unknown, but similar to Paramecium aurelia, Allogromia laticollaris is also shown to sometimes defer to autogamous behavior when placed in nutritional stress. As seen in Paramecium, there is some nuclear dimorphism observed in Allogromia laticollaris.
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Self- fertilization (selfing, or autogamy) is more common in annual compared to perennial herbs. Since annuals typically have only one opportunity for reproduction, selfing provides a reliable source of fertilization. However, switches to selfing in annuals may result in an "evolutionary dead end," in the sense that it is probably unlikely to return to an outcrossing (allogamous) state. Selfing and inbreeding can also result in the accumulation of deleterious alleles, resulting in inbreeding depression.
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When two filaments of opposing mating types come close together, the cells form conjugation tubes between the filaments. Once the tubes are formed, one cell balls up and crawls through the tube into the other cell to fuse with it, forming a zygote. In ciliates, cell fission may follow self-fertilization (autogamy), or it may follow conjugation (exchange of nuclei). In zygomycetes fungi, two hyphae of opposing mating types form special structures called gametangia where the hyphae touch.
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Protists have the advantage of diversifying their modes of reproduction. This is useful for a multitude of reasons. First, if there is an unfavorable change in the environment that puts the ability to deliver offspring at risk, then it is advantageous for an organism to have autogamy at its disposal. In other organisms, it is seen that genetic diversity arising from sexual reproduction is maintained by changes in the environment that favor certain genotypes over others.
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Actinophrys undergoing multiple plasmotomy Reproduction in actinophryids generally takes place via fission, where one parent cell divides into two or more daughter cells. For multinucleate heliozoa, this process is plasmotomic as the nuclei are not duplicated prior to division. It has been observed that reproduction appears to be a response to food scarcity, with an increased number of divisions following the removal of food and larger organisms during times of food excess. Actinophryids also undergo autogamy during times of food scarcity.
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In 2005 van Roestenberg organized Autogamy, an event which gave participants the opportunity to experience what it was like to plan his wedding. van Roestenberg served five years on the Zoning Board of Appeals, over two years on the zoning commission, and served as Vice Chair of the town Democratic Commission. Van Roestenberg made an unsuccessful bid for County Legislature on the Democratic ticket in 2005. In 2010, van Roestenberg organized the "Unhappy Anniversary" to commemorate the sixth anniversary of the New Paltz same-sex weddings.
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The primary mating systems in plants are outcrossing (cross-fertilisation), autogamy (self-fertilisation) and apomixis (asexual reproduction without fertilization, but only when arising by modification of sexual function). Mixed mating systems, in which plants use two or even all three mating systems, are not uncommon. A number of models have been used to describe the parameters of plant mating systems. The basic model is the mixed mating model, which is based on the assumption that every fertilisation is either self-fertilisation or completely random cross-fertilisation.
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There are several advantages for the self- fertilization observed in flowering plants and protists. In flowering plants, it is important for some plants not to be dependent on pollinating agents that other plants rely on for fertilization. This is unusual, however, considering that many plant species have evolved to become incompatible with their own gametes. While these species would not be well served by having autogamous self-fertilization as a reproductive mechanism, other species, which do not have self-incompatibility, would benefit from autogamy.
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However, other types of fission occur in some ciliate groups. These include budding (the emergence of small ciliated offspring, or "swarmers", from the body of a mature parent); strobilation (multiple divisions along the cell body, producing a chain of new organisms); and palintomy (multiple fissions, usually within a cyst). Fission may occur spontaneously, as part of the vegetative cell cycle. Alternatively, it may proceed as a result of self- fertilization (autogamy), or it may follow conjugation, a sexual phenomenon in which ciliates of compatible mating types exchange genetic material.
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For example, in the short-styled morph, the two sets of stamen are arranged in the mid and long position in order to prevent autogamy. In trimorphic incompatibility system, full seed set is accomplished only with pollination of stigmas by pollen from anthers of the same height. This incompatibility system produces pollen and styles with three different incompatibility phenotypes because of the three style and stamen lengths. Tristylous species have been found in several angiosperm families including the Oxalidaceae, Pontederiaceae, Amaryllidaceae, Connaraceae, Linaceae and Lythraceae, though several others have been proposed.
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The fixation of a single allele for a specific gene can also reduce fitness where heterozygote advantage was previously present (i.e., where heterozygous individuals have higher fitness than homozygotes of either allele), although this phenomenon seems to make a usually small contribution to inbreeding depression. Although naturally occurring, purging can be important for population survival, deliberately attempting to purge deleterious mutations from a population is not generally recommended as a technique to improve the fitness of captive bred animals. In plants, genetic load can be assessed through a test analogous to an inbreeding depression test called an Autogamy depression test.
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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 when pollen from the same plant arrives at the stigma of a flower (in flowering plants) or at the ovule (in gymnosperms). 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.
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Reproductive assurance (fertility assurance) occurs as plants have mechanisms to assure full seed set through selfing when outcross pollen is limiting. It is assumed that self-pollination is beneficial, in spite of potential fitness costs, when there is insufficient pollinator services or outcross pollen from other individuals to accomplish full seed set.. This phenomenon has been observed since the 19th century, when Darwin observed that self-pollination was common in some plants. Constant pollen limitation may cause the evolution of automatic selfing, also known as autogamy. This occurs in plants such as weeds, and is a form of reproductive assurance.
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The macronucleus controls non-reproductive cell functions, expressing the genes needed for daily functioning. The micronucleus is the generative, or germline nucleus, containing the genetic material that is passed along from one generation to the next. In the asexual fission phase of growth, during which cell divisions occur by mitosis rather than meiosis, clonal aging occurs leading to a gradual loss of vitality. In some species, such as the well studied Paramecium tetraurelia, the asexual line of clonally aging paramecia loses vitality and expires after about 200 fissions if the cells fail to undergo meiosis followed by either autogamy (self-fertilization) or conjugation (outcrossing) (see aging in Paramecium).
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DNA damage increases dramatically during successive clonal cell divisions and is a likely cause of clonal aging in P. tetraurelia. When clonally aged P. tetraurelia are stimulated to undergo meiosis in association with either autogamy or conjugation, the progeny are rejuvenated, and are able to have many more mitotic binary fission divisions. During either of these processes the micronuclei of the cell(s) undergo meiosis, the old macronucleus disintegrates and a new macronucleus is formed by replication of the micronuclear DNA that had recently undergone meiosis. There is apparently little, if any, DNA damage in the new macronucleus, suggesting that rejuvenation is associated with the repair of these damages in the micronucleus during meiosis.
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