Letteratura scientifica selezionata sul tema "Asexuel"
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Articoli di riviste sul tema "Asexuel"
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Key, Adam. "The Silent A". Journal of Autoethnography 2, n. 4 (2021): 446–65. http://dx.doi.org/10.1525/joae.2021.2.4.446.
Testo completoAbstract (sommario):
This critical autoethnography explores experiences as an asexual cismale and the inherent tensions and struggles experienced in the dialectic between societal expectations of sexual desire as a man and the lack of sex drive characteristic of an asexual orientation. It explores the exclusion asexuals experience, as they occupy a third space between straightness and queerness, leaving them nowhere in either the gender or sexuality roles spectrums to truly call home. As asexuals exist in a space not often considered by heterosexual and queer individuals and asexual men exist between the tension of sexual expectation and orientation, music is utilized as a means of common language. This essay offers this connection through a series of autoethnographic glimpses, each set to a different song or lyric, as a soundtrack to give voice to the silenced experiences of asexuals.
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Tobler, M., e I. Schlupp. "Expanding the horizon: the Red Queen and potential alternatives". Canadian Journal of Zoology 86, n. 8 (agosto 2008): 765–73. http://dx.doi.org/10.1139/z08-056.
Testo completoAbstract (sommario):
The Red Queen hypothesis (RQH) is one of the most widely accepted hypotheses explaining the persistence of sexual reproduction despite its costs. It posits that sexual species, compared with asexuals, are more adept at countering parasites, because their per-generation recombination rate is higher. Despite theoretical support, current empirical studies have failed to provide unanimous support. Here, we suggest that future tests of the RQH should more thoroughly elucidate its underlying assumptions and potential alternative hypotheses. While the RQH predicts that negative frequency-dependent selection shapes host–parasite interactions, differences between sexuals and asexuals are potentially important. Key assumptions about asexual species and their sexual close relatives include (i) ecological and behavioral traits are similar, (ii) among-individual genetic diversity is greater in sexuals than in asexuals, and (iii) within-individual genetic diversity is similar in asexuals and sexuals. We review current evidence for the RQH, highlight differences between asexual and sexual species and how those differences might translate into differential responses to parasite infections, and discuss how they can influence the results and interpretation of empirical studies. Considering differences between asexual and sexual species in future tests of the RQH will help to refine predictions and eliminate alternative hypotheses.
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Scheu, S., e B. Drossel. "Sexual reproduction prevails in a world of structured resources in short supply". Proceedings of the Royal Society B: Biological Sciences 274, n. 1614 (27 febbraio 2007): 1225–31. http://dx.doi.org/10.1098/rspb.2007.0040.
Testo completoAbstract (sommario):
We present a model for the maintenance of sexual reproduction based on the availability of resources, which is the strongest factor determining the growth of populations. The model compares completely asexual species to species that switch between asexual and sexual reproduction (sexual species). Key features of the model are that sexual reproduction sets in when resources become scarce, and that at a given place only a few genotypes can be present at the same time. We show that under a wide range of conditions the sexual species outcompete the asexual ones. The asexual species win only when survival conditions are harsh and death rates are high, or when resources are so little structured or consumer genotypes are so manifold that all resources are exploited to the same extent. These conditions, largely represent the conditions in which sexuals predominate over asexuals in the field.
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Larose, Chloé, Darren J. Parker e Tanja Schwander. "Fundamental and realized feeding niche breadths of sexual and asexual stick insects". Proceedings of the Royal Society B: Biological Sciences 285, n. 1892 (28 novembre 2018): 20181805. http://dx.doi.org/10.1098/rspb.2018.1805.
Testo completoAbstract (sommario):
The factors contributing to the maintenance of sex over asexuality in natural populations remain unclear. Ecological divergences between sexual and asexual lineages could help to maintain reproductive polymorphisms, at least transiently, but the consequences of asexuality for the evolution of ecological niches are unknown. Here, we investigated how niche breadths change in transitions from sexual reproduction to asexuality. We used host plant ranges as a proxy to compare the realized feeding niche breadths of five independently derived asexual Timema stick insect species and their sexual relatives at both the species and population levels. Asexual species had systematically narrower realized niches than sexual species, though this pattern was not apparent at the population level. To investigate how the narrower realized niches of asexual species arise, we performed feeding experiments to estimate fundamental niche breadths but found no systematic differences between reproductive modes. The narrow realized niches found in asexual species are therefore probably a consequence of biotic interactions such as predation or competition, that constrain realized niche size in asexuals more strongly than in sexuals.
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Riesch, Rüdiger, Ingo Schlupp e Martin Plath. "Female sperm limitation in natural populations of a sexual/asexual mating complex ( Poecilia latipinna , Poecilia formosa )". Biology Letters 4, n. 3 (4 marzo 2008): 266–69. http://dx.doi.org/10.1098/rsbl.2008.0019.
Testo completoAbstract (sommario):
In sperm-dependent sexual/asexual mating systems, male mate choice is critical for understanding the mechanisms behind apparent stability observed in natural populations. The gynogenetic Amazon molly ( Poecilia formosa ) requires sperm from sexual males (e.g. Poecilia latipinna ) to trigger embryogenesis, but inheritance is strictly maternal. Consequently, males should try to avoid or reduce the cost of mating with asexuals. We investigated male mate choice by documenting the presence of sperm in natural populations and found that a higher proportion of sexual females had sperm than asexuals. In addition, among those females that had sperm, sexuals had more sperm than asexuals. Our results hint at a role for male mate choice as a stabilizing factor in such systems.
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Carranza, Juan, e Vicente Polo. "Sexual reproduction with variable mating systems can resist asexuality in a rock–paper–scissors dynamics". Royal Society Open Science 2, n. 7 (luglio 2015): 140383. http://dx.doi.org/10.1098/rsos.140383.
Testo completoAbstract (sommario):
While sex can be advantageous for a lineage in the long term, we still lack an explanation for its maintenance with the twofold cost per generation. Here we model an infinite diploid population where two autosomal loci determine, respectively, the reproductive mode, sexual versus asexual and the mating system, polygynous (costly sex) versus monogamous (assuming equal contribution of parents to offspring, i.e. non-costly sex). We show that alleles for costly sex can spread when non-costly sexual modes buffer the interaction between asexual and costly sexual strategies, even without twofold benefit of recombination with respect to asexuality. The three interacting strategies have intransitive fitness relationships leading to a rock–paper–scissors dynamics, so that alleles for costly sex cannot be eliminated by asexuals in most situations throughout the parameter space. Our results indicate that sexual lineages with variable mating systems can resist the invasion of asexuals and allow for long-term effects to accumulate, thus providing a solution to the persisting theoretical question of why sex was not displaced by asexuality along evolution.
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Amat, Isabelle, Jacques J. M. van Alphen, Alex Kacelnik, Emmanuel Desouhant e Carlos Bernstein. "Adaptations to different habitats in sexual and asexual populations of parasitoid wasps: a meta-analysis". PeerJ 5 (12 settembre 2017): e3699. http://dx.doi.org/10.7717/peerj.3699.
Testo completoAbstract (sommario):
BackgroundCoexistence of sexual and asexual populations remains a key question in evolutionary ecology. We address the question how an asexual and a sexual form of the parasitoidVenturia canescenscan coexist in southern Europe. We test the hypothesis that both forms are adapted to different habitats within their area of distribution. Sexuals inhabit natural environments that are highly unpredictable, and where density of wasps and their hosts is low and patchily distributed. Asexuals instead are common in anthropic environments (e.g., grain stores) where host outbreaks offer periods when egg-load is the main constraint on reproductive output.MethodsWe present a meta-analysis of known adaptations to these habitats. Differences in behavior, physiology and life-history traits between sexual and asexual wasps were standardized in term of effect size (Cohen’sdvalue; Cohen, 1988).ResultsSeeking consilience from the differences between multiple traits, we found that sexuals invest more in longevity at the expense of egg-load, are more mobile, and display higher plasticity in response to thermal variability than asexual counterparts.DiscussionThus, each form has consistent multiple adaptations to the ecological circumstances in the contrasting environments.
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Stelzer, Claus-Peter. "Does the avoidance of sexual costs increase fitness in asexual invaders?" Proceedings of the National Academy of Sciences 112, n. 29 (21 luglio 2015): 8851–58. http://dx.doi.org/10.1073/pnas.1501726112.
Testo completoAbstract (sommario):
The high prevalence of sexual reproduction is considered a paradox mainly for two reasons. First, asexuals should enjoy various growth benefits because they seemingly rid themselves of the many inefficiencies of sexual reproduction—the so-called costs of sex. Second, there seems to be no lack of asexual origins because losses of sexual reproduction have been described in almost every larger eukaryotic taxon. Current attempts to resolve this paradox concentrate on a few hypotheses that provide universal benefits that would compensate for these costs and give sexual reproduction a net advantage. However, are new asexual lineages really those powerful invaders that could quickly displace their sexual ancestors? Research on the costs of sex indicates that sex is often stabilized by highly lineage-specific mechanisms. Two main categories can be distinguished. First are beneficial traits that evolved within a particular species and became tightly associated with sex (e.g., a mating system that involves sexual selection, or a sexual diapausing stage that allows survival through harsh periods). If such traits are absent in asexuals, simple growth efficiency considerations will not capture the fitness benefits gained by skipping sexual reproduction. Second, lineage-specific factors might prevent asexuals from reaching their full potential (e.g., dependence on fertilization in sperm-dependent parthenogens). Such observations suggest that the costs of sex are highly variable and often lower than theoretical considerations suggest. This has implications for the magnitude of universal benefits required to resolve the paradox of sex.
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Stelzer, Claus-Peter, e Jussi Lehtonen. "Diapause and maintenance of facultative sexual reproductive strategies". Philosophical Transactions of the Royal Society B: Biological Sciences 371, n. 1706 (19 ottobre 2016): 20150536. http://dx.doi.org/10.1098/rstb.2015.0536.
Testo completoAbstract (sommario):
Facultative sex combines sexual and asexual reproduction in the same individual (or clone) and allows for a large diversity of life-history patterns regarding the timing, frequency and intensity of sexual episodes. In addition, other life-history traits such as a diapause stage may become linked to sex. Here, we develop a matrix modelling framework for addressing the cost of sex in facultative sexuals, in constant, periodic and stochastically fluctuating environments. The model is parametrized using life-history data from Brachionus calyciflorus , a facultative sexual rotifer in which sex and diapause are linked. Sexual propensity was an important driver of costs in constant environments, in which high costs (always > onefold, and sometimes > twofold) indicated that asexuals should outcompete facultative sexuals. By contrast, stochastic environments with high temporal autocorrelation favoured facultative sex over obligate asex, in particular, if the penalty to fecundity in ‘bad’ environments was large. In such environments, obligate asexuals were constrained by their life cycle length (i.e. time from birth to last reproductive adult age class), which determined an upper limit to the number of consecutive bad periods they could tolerate. Nevertheless, when facultative asexuals with different sexual propensities competed simultaneously against each other and asex, the lowest sex propensity was the most successful in stochastic environments with positive autocorrelation. Our results suggest that a highly specific mechanism (i.e. diapause linked to sex) can alone stabilize facultative sex in these animals, and protect it from invasion of both asexual and pure sexual strategies. This article is part of the themed issue ‘Weird sex: the underappreciated diversity of sexual reproduction’.
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Choleva, Lukáš, Apostolos Apostolou, Petr Ráb e Karel Janko. "Making it on their own: sperm-dependent hybrid fishes ( Cobitis ) switch the sexual hosts and expand beyond the ranges of their original sperm donors". Philosophical Transactions of the Royal Society B: Biological Sciences 363, n. 1505 (2 giugno 2008): 2911–19. http://dx.doi.org/10.1098/rstb.2008.0059.
Testo completoAbstract (sommario):
Interspecific hybridization may result in asexual hybrid lineages that reproduce via parthenogenesis. Contrary to true parthenogens, sperm-dependent asexuals (gynogens and hybridogens) are restricted to the range of bisexual species, generally the parental taxa, by their need for a sperm donor. It has been documented that asexual lineages may rarely use sperm from a non-parental species or even switch a host. The available literature reports do not allow distinguishing, between whether such host switches arise by the expansion of asexuals out of their parental's range (and into that of another's) or by the local extinction of a parental population followed by a host switch. The present study combines new and previously collected data on the distribution and history of gynogenetic spined loaches ( Cobitis ) of hybrid origin. We identified at least three clonal lineages that have independently switched their sperm dependency to different non-parental Cobitis species, and in cases incorporated their genomes. Our current knowledge of European Cobitis species and their hybrids suggests that this pattern most probably results from the expansion of gynogenetic lineages into new areas. Such expansion was independent of the original parental species. This suggests that sperm dependence is not as restrictive to geographical expansion when compared with true parthenogenesis as previously thought.
Tesi sul tema "Asexuel"
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De, Ory Zoé. "Un non-désir qui dit son nom : enquête sur une auto-identification émergente, l'asexualité". Electronic Thesis or Diss., Paris, EHESS, 2024. http://www.theses.fr/2024EHES0048.
Testo completoAbstract (sommario):
À la croisée de la sociologie de la « déviance », de la sociologie de la sexualité et du genre, et de la critique des sciences, cette thèse porte sur un groupe social émergent : les personnes qui s'identifient en tant qu'asexuelles. Venant compléter d'un A le sigle LGBTQIA (+), ces personnes revendiquent une absence de désir et/ou d'attirance sexuelle pour autrui. La recherche s'appuie principalement sur une enquête qualitative par entretiens. Ont été recueillis et analysés les discours, revendications et récits autobiographiques de personnes asexuelles auto-identifiées résidant en France, militantes ou non. Ont aussi été interrogés un ensemble de sexologues et de psychothérapeutes, ainsi qu'un groupe témoin de personnes ne s'identifiant pas à l'asexualité et rapportant des « problèmes » dans leur vie sexuelle. Des événements collectifs (réunions, Marche des fiertés, congrès de sexologie) ont également été observés. L'idée, par ce travail et l'articulation de ces divers matériaux, était d'une part de s'intéresser en profondeur à cette auto-identification historiquement très récente, d'en mieux cerner les contours, les caractéristiques et les enjeux, et d'autre part de questionner le traitement social ordinaire du non-désir sexuel pour autrui, le plus souvent impensé ou implicitement problématisé, à la lumière des normes d'hier et d'aujourd'hui, de sexualité, de genre, de santé, d'identitéThis thesis uses tools from labelling theory, sociology of “deviance”, sociology of sexuality and gender and criticism of science to focus on an emergent social group: individuals who self-identify as asexual, completing the acronym LGBTQIA(+) and reporting an absence of sexual desire for and/or sexual attraction to others. The dissertation is based on a qualitative survey and on a series of interviews. Discourses and trajectories of French self-identified asexuals (vocal activists or not) have been collected and analyzed. Sexologists and psychotherapists, and individuals having reported some sexual “issues” (without asexual self-identification) have also been interviewed. Finally, collective/community events (meetings, LGBT/Gay Pride, sexology conference in France) have been observed. The purpose of this research was, first of all, to study in detail this recent self-identification (asexuality) in order to better understand its characteristics and its implications, its words and its actions. Moreover, this work tries to highlight the ordinary conception of non-desire, and to propose a reflection, through asexuality, on sexuality, gender, health and identity standards
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Ricci, Lorenzo. "A new model to study alternative developments : asexual propagation and regeneration in the basal chordate Botryllus schlosseri". Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066683.
Testo completoAbstract (sommario):
Chez l’ascidie coloniale Botryllus schlosseri, en plus de l’embryogénèse existent deux voies de développement aboutissant à la production de la même structure : l’organisme adulte ou zooide. Ces développements alternatifs ont lieu lors de processus biologiques distincts : le bourgeonnement palléal (BP) et le bourgeonnement vasculaire (BV). Le BP est un processus de multiplication asexuée présentant une ontogénèse stéréotypée. En revanche, le BV est un phénomène régénératif, induit dans les vaisseaux sanguins de la colonie par l’ablation de tous les zooides et bourgeons palléaux. Mes travaux de recherche ont eu pour objectif de caractériser les bases moléculaires et cellulaires régissant le BP et le BV chez B. schlosseri. L’étude de gènes marqueurs des lignées méso-, endo- et ectodermiques a révélé l’existence de territoires présomptifs pour chacune de ces lignées, dès les premiers stades du BV et du BP, et suggéré l’existence d’un programme unique aux deux processus. Les lignées neurales et musculaires ont été étudiées plus en détail lors du BP, indiquant un double rôle potentiel, neuro- et myo-génétique, au tube dorsal, une structure jusqu’à présent uniquement associée au système nerveux. Une caractérisation morphologique poussée a mené à l’identification de stades précoces stéréotypés du BV lors de la régénération. Enfin, l’analyse de transcriptomes de différents stades du BP et de la régénération ont initié l’étude non biaisée des bases moléculaires du bourgeonnement chez Botryllus. L’objectif à long terme de ces travaux est de décrypter les bases moléculaires et génétiques facilitant, chez les métazoaires, l’évolution de voies de développement alternativesIn addition to embryogenesis, the colonial ascidians Botryllus schlosseri evolved two alternative developmental pathways leading to the same final structure: the adult body, or zooid. These non-embryonic ontogenesis occur during distinct biological processes: palleal budding (PB) and vascular budding (VB). PB is a process of asexual propagation, with a very stereotyped morphogenesis. Conversely, VB is a purely regenerative phenomenon, induced in the vascular system of the colony by the ablation of all zooids and palleal buds. My research work followed the objective to characterize the molecular and cellular basis of both PB and VB in B. schlosseri. The study of meso-, endo- and ectodermal lineage marker genes revealed the existence of presumptive territories of these lineages in the early palleal and vascular buds and that a single developmental program was launched in both VB and PB. Neural and muscle fates were studied in more detail for PB, indicating a potential double function, both neuro- and myo-genic for the dorsal tube, a structure so far associated with the nervous system only. A detailed morphological description of VB allowed to identify stereotyped stages during early regeneration. Eventually, a transcriptomic characterization of early VB and PB processes initiated an unbiased study of the molecular basis underlying the budding phenomenon in Botryllus. The overall goal of these research works is to unravel the molecular and genetic basis that facilitated, in Botryllus and globally in metazoan, the evolution of alternative developmental pathways
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Puisay, Antoine. "La reproduction sexuée et asexuée des coraux face aux changements environnementaux : Implications pour la conservation et la restauration des récifs coralliens". Thesis, Paris Sciences et Lettres (ComUE), 2018. http://www.theses.fr/2018PSLEP030.
Testo completoAbstract (sommario):
Le changement climatique et l’augmentation des températures globales perturbent l’abondance et la distribution de milliers d’organismes, aquatiques et terrestres, et certains écosystèmes sont particulièrement sensibles à ces changements environnementaux. L’augmentation de température est la principale menace au maintien des populations de coraux, véritables ingénieurs écologiques de ces écosystèmes. Bien que la recherche sur les récifs coralliens se soit d’abord attachée à l’étude des coraux adultes, de nombreuses informations manquent sur la reproduction sexuée et asexuée, et leur rôle dans la conservation et restauration récifale. Le premier axe de ma thèse s’est donc construit sur la réponse des jeunes stades de vie à l’augmentation de température, pour d’abord évaluer les modifications de leur performance et ensuite évaluer dans quelles mesures les jeunes stades seraient capables de s’acclimater à des conditions de températures plus élevées. Au travers de différentes expérimentations en laboratoire sur le genre Acropora, j’ai ainsi mis en évidence 1) une résistance thermique importante (+2-3°C au-dessus des températures ambiantes) des gamètes face à l’augmentation de température, 2) une résistance thermique différente entre spermatozoïdes et ovocytes: ovocytes < spermatozoïdes, 3) et la mise en évidence du rôle majeur de l’environnement dans lequel se rencontre les gamètes une fois libérés, sur la qualité et la quantité de la fécondation. Enfin, j’ai identifié les conditions optimales thermiques de pré-exposition des gamètes pour maximiser leur succès de fécondation. Bien qu’un intérêt croissant soit porté sur la reproduction sexuée ces dernières années, l’utilisation de la reproduction asexuée demeure la méthode la plus utilisée pour restaurer les récifs coralliens, plus connue sous le nom de bouturage. Ainsi le second axe de ma thèse a cherché à mettre en évidence la plasticité phénotypique des coraux en cultivant des boutures provenant de 3 espèces dans 3 environnements différents et en analysant leur taux de croissance, leur état de santé et leur survie. Cet axe a pu montrer qu’il existait des différences à plusieurs échelles, entre espèces, mais aussi au sein d’une même espèce. Mes travaux montrent qu’une sélection des individus basée sur l’étude de la plasticité phénotypique de certains traits d’histoires de vie comme la croissance ou l’état de santé dans des environnements variables permettrait d’améliorer l’efficacité de la restauration récifale. Ainsi le choix des individus au sein d’une même espèce afin de réaliser du bouturage (reproduction asexuée) et le conditionnement de la phase de vie gamètes (reproduction sexuée) peut permettre d’augmenter l’efficacité des méthodes de restaurations tout en nous donnant des informations nouvelles sur la biologie et la physiologie des coraux scléractiniaires face aux changements environnementauxClimate change and increasing temperature impact abundance and distribution of thousands of organisms, aquatic and terrestrial, and some ecosystems are particularly sensitive to these global changes. Increasing temperature is the principal threat for coral populations, which are ecological engineers of coral reef ecosystems. While research on coral reefs has first sought to study adult corals, data are still lacking on early life stages of corals. As sexual and asexual reproduction may play a key role in the conservation and restoration of coral reefs, my doctoral research aims to better understand changes on sexual and asexual reproduction in the face of rising temperature. The first axis of my Ph. D. was built on the response of early life stages to increasing temperature, in order to assess whether pre-exposure of early life may improve their ulterior performance. Among the different experiments performed on the genus Acropora, I highlighted 1) a high thermal tolerance (+2-3°C above ambient temperature) of gametes, 2) a higher sensibility of oocytes than sperm to rising temperature exposure, and 3) the pivotal role of gamete thermal history on fertilization output. Finally, I identified optimal pre-exposure conditions in order to maximize fertilization success. While an increasing interest in sexual reproduction was observed these last years, asexual reproduction and fragmentation still remain the main tool to restore damaged reefs. Thus, in the second axis of my doctoral project, I investigated the phenotypic plasticity of corals by growing 3 different species of corals across 3 different environments. Their growth rates, health status and survival probability were determined. Results from this axis showed that differences were observed at the interspecific and intraspecific levels. This work revealed that a selection based on phenotypic plasticity among different life-traits (growth rates and health status) and different environments should allow to increase coral reef restoration strategies. Hence the selection of individuals (asexual reproduction) in a species based on coral common garden experiment allow to identify individuals of interest to use as restoration biological materials. Additionally, thermal pre-conditioning of early life stages (sexual reproduction) is another way to increase efficiency of restoration measures in the face of rising temperature. My doctoral research provided new information regarding physiological and biological processes of scleractinian corals facing environmental changes and proposed new solutions for restorations based on sexual and/or asexual reproduction
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Kozlowski, Djampa. "Contribution des éléments transposables à l’adaptabilité de ravageurs de cultures en absence de reproduction sexuée". Electronic Thesis or Diss., Université Côte d'Azur, 2020. http://www.theses.fr/2020COAZ6028.
Testo completoAbstract (sommario):
Les nématodes à galles (genre Meloidogyne) sont parmi les parasites de plantes les plus nuisibles. Ces organismes se distinguent par la diversité de leurs modes de reproduction. Étonnement, il a été observé que les espèces les plus néfastes se reproduisent de manière strictement asexuée et certaines sont capables de contourner la résistance de la plante hôte en un nombre de générations restreint. Ainsi, bien qu'incapables de combiner des mutations bénéfiques provenant de différents individus, ces espèces peuvent s'adapter à des changements du milieu. L’adaptabilité et le succès parasitaire de ces espèces malgré l’absence de reproduction sexuée semblent paradoxaux et doivent reposer sur d’autres mécanismes capables de générer de la plasticité génétique.Les éléments transposables (ETs) sont des fragments d’ADN capables de se déplacer et de se multiplier dans les génomes. De ce fait, les ETs peuvent avoir des répercussions fonctionnelles et structurales sur les génomes. Les ETs pourraient constituer un des mécanismes permettant de générer la diversité génétique nécessaire à l’adaptabilité chez Meloidogyne.En réalisant une analyse de génomique comparative entre 7 espèces de Meloidogyne, j’ai montré que le contenu en ETs actuellement observé chez ces espèces semble suivre leur histoire évolutive et la dérive entre espèces, plutôt que des traits d’histoires de vie tels que le mode de reproduction. Par ailleurs, cette analyse soutient une activité récente des ETs au sein de la plupart des espèces. Ces résultats suggèrent que bien que les ETs aient récemment été actifs au sein du genre Meloidogyne, leur dynamique dans les génomes semble spécifique à chaque espèce et nécessite donc une étude ciblée.Dans cette optique, j’ai concentré mes efforts sur M. incognita, l’espèce à reproduction asexuée la plus préjudiciable pour l’agriculture. Dans un premier temps, j’ai annoté en détail le contenu en ETs du génome de M. incognita. L’analyse du contenu en ETs a confirmé que ces éléments ont probablement été récemment actifs dans le génome. Afin de mieux caractériser cette activité et ses potentiels effets, j’ai ensuite estimé la mobilité de ces ETs via une analyse de génomique comparative portant sur 12 isolats géographiques. J’ai pu identifier plusieurs milliers de loci dans le génome où les fréquences de présence d'ETs varient entre les différents isolats. Par une approche phylogénétique, j’ai montré que ces variations de fréquence d’ETs suivent l’histoire évolutive des isolats étudiés. Par rapport au génome de référence, j’ai prédit des néo-insertions d’ETs, certaines ayant un potentiel impact fonctionnel. Les validations expérimentales réalisées pour plusieurs de ces insertions confirment le rôle probable des ETs dans la plasticité du génome de cette espèce.Lors de cette analyse, j’ai également identifié des ETs présents à des fréquences intermédiaires (différentes de 0 ou 1) au sein de chaque isolat, signe d’une variabilité entre individus. Or M. incognita est un organisme supposé clonal et chaque isolat étudié est issu d’une seule femelle. En nous concentrant sur l’analyse d’un de ces isolats, nous avons validé expérimentalement plusieurs polymorphismes de présence, ce qui confirme qu’il existe une hétérogénéité génétique non négligeable au sein d’un même isolat. Par ailleurs, en comparant des données de séquençage issues du même isolat à deux points de cinétique différents, nous avons pu prédire que quelques ETs varient en fréquences au sein de l’isolat en un faible nombre de générations, ce qui sous-entend que ces ETs participent à la dynamique de la diversité génétique de cet organisme. Ces résultats posent les bases pour de futures analyses visant à déterminer si l'activité des ETs joue un rôle actif dans la capacité d’espèces à s'adapter à leur environnement en absence de reproduction sexuéeRoot-knot nematodes (genus Meloidogyne) are among the most devastating plant parasites. These organisms present an important diversity of reproductive modes. Surprisingly, it has been observed that the most damaging species reproduce in a strictly asexual manner and some can bypass the host plant's resistance in a limited number of generations. Thus, although being unable to combine beneficial mutations from different individuals, these species can adapt to environmental changes. The adaptability and parasitic success of these species despite the absence of sexual reproduction seem paradoxical and must rely on other mechanisms capable of generating genetic plasticity. Transposable Elements (TEs) are DNA fragments capable of moving and multiplying in genomes. As a result, TEs can have functional and structural repercussions on genomes. Hence, TEs could be one of the mechanisms involved in generating the genetic diversity necessary for adaptability in Meloidogyne.By performing a comparative genomics analysis between 7 Meloidogyne species, I have shown that the TE landscape currently observed in these species seems to follow their evolutionary history and interspecies drift rather than life-history traits such as the reproduction mode. Furthermore, this analysis supports recent TE activity within all these species. The results also suggest that although TEs have recently been active within the genus Meloidogyne, their dynamics in the genomes appear to be species-specific and thus require targeted study.With this in mind, I have focused my efforts on M. incognita, arguably the most detrimental asexually reproductive species to agriculture. As a first step, I have annotated in detail the TE content in the genome of M. incognita. The TE content analysis confirmed these elements have probably been recently active in the genome. To better characterize this activity and its potential effects, I then estimated the mobility of these TEs through a comparative genomics analysis of 12 geographic isolates. I was able to identify several thousand loci in the genome where the frequencies of TE presence varied substantially between different isolates. Using a phylogenetic approach, I showed that these TE frequency variations followed the evolutionary history of the studied isolates. Compared to the reference genome, I have predicted TE neo-insertions, some with potential functional impact. Experimental validations carried out for several of these insertions confirmed the potential role of TEs in the genome plasticity in this species.During this analysis, I also identified TEs present at intermediate frequencies (different from 0 or 1) within each isolate, indicating variability between individuals despite the fact M. incognita is a supposedly clonal organism and that each isolate studied was derived from a single female. Focusing on the analysis of one of these isolates, we have experimentally validated several TE polymorphisms, confirming that there is significant genetic heterogeneity within the same isolate. Furthermore, by comparing sequencing data from the same isolate at two different time points, we predicted that a few TEs varied in frequency within the isolate within a small number of generations, implying these TEs participate in the dynamics of genetic diversity in this organism. These results lay the foundation for future analyses to determine whether TEs play an active role in the ability of species to adapt to their environment in the absence of sexual reproduction
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Ricci, Lorenzo. "A new model to study alternative developments : asexual propagation and regeneration in the basal chordate Botryllus schlosseri". Electronic Thesis or Diss., Paris 6, 2015. http://www.theses.fr/2015PA066683.
Testo completoAbstract (sommario):
Chez l’ascidie coloniale Botryllus schlosseri, en plus de l’embryogénèse existent deux voies de développement aboutissant à la production de la même structure : l’organisme adulte ou zooide. Ces développements alternatifs ont lieu lors de processus biologiques distincts : le bourgeonnement palléal (BP) et le bourgeonnement vasculaire (BV). Le BP est un processus de multiplication asexuée présentant une ontogénèse stéréotypée. En revanche, le BV est un phénomène régénératif, induit dans les vaisseaux sanguins de la colonie par l’ablation de tous les zooides et bourgeons palléaux. Mes travaux de recherche ont eu pour objectif de caractériser les bases moléculaires et cellulaires régissant le BP et le BV chez B. schlosseri. L’étude de gènes marqueurs des lignées méso-, endo- et ectodermiques a révélé l’existence de territoires présomptifs pour chacune de ces lignées, dès les premiers stades du BV et du BP, et suggéré l’existence d’un programme unique aux deux processus. Les lignées neurales et musculaires ont été étudiées plus en détail lors du BP, indiquant un double rôle potentiel, neuro- et myo-génétique, au tube dorsal, une structure jusqu’à présent uniquement associée au système nerveux. Une caractérisation morphologique poussée a mené à l’identification de stades précoces stéréotypés du BV lors de la régénération. Enfin, l’analyse de transcriptomes de différents stades du BP et de la régénération ont initié l’étude non biaisée des bases moléculaires du bourgeonnement chez Botryllus. L’objectif à long terme de ces travaux est de décrypter les bases moléculaires et génétiques facilitant, chez les métazoaires, l’évolution de voies de développement alternativesIn addition to embryogenesis, the colonial ascidians Botryllus schlosseri evolved two alternative developmental pathways leading to the same final structure: the adult body, or zooid. These non-embryonic ontogenesis occur during distinct biological processes: palleal budding (PB) and vascular budding (VB). PB is a process of asexual propagation, with a very stereotyped morphogenesis. Conversely, VB is a purely regenerative phenomenon, induced in the vascular system of the colony by the ablation of all zooids and palleal buds. My research work followed the objective to characterize the molecular and cellular basis of both PB and VB in B. schlosseri. The study of meso-, endo- and ectodermal lineage marker genes revealed the existence of presumptive territories of these lineages in the early palleal and vascular buds and that a single developmental program was launched in both VB and PB. Neural and muscle fates were studied in more detail for PB, indicating a potential double function, both neuro- and myo-genic for the dorsal tube, a structure so far associated with the nervous system only. A detailed morphological description of VB allowed to identify stereotyped stages during early regeneration. Eventually, a transcriptomic characterization of early VB and PB processes initiated an unbiased study of the molecular basis underlying the budding phenomenon in Botryllus. The overall goal of these research works is to unravel the molecular and genetic basis that facilitated, in Botryllus and globally in metazoan, the evolution of alternative developmental pathways
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Cortes, Blanca R. "Horizontal genetic transfer in asexual fungi". FIU Digital Commons, 2000. http://digitalcommons.fiu.edu/etd/2644.
Testo completoAbstract (sommario):
Four aspects of horizontal genetic transfer during heterokaryon formation were examined in the asexual pathogen Fusarium oxysporum f.sp. cubense (Foe): 1) variability based on method of heterokaryon formation 2) differences in nuclear and mitochondrial inheritance 3) the occurrence of recombination without nuclear fusion 4) the occurrence of horizontal genetic transfer between distantly related isolates. The use of non- pathogenic strains of Fusarium oxysporum as biocontrol agents warrants a closer examination at the reproductive life cycle of this fungus, particularly if drag resistance or pathogenicity genes can be transmitted horizontally. Experiments were divided into three phases. Phase I looked at heterokaryon formation by hyphal anastomosis and protoplast fusion. Phase II was a time course of heterokaryon formation to look at patterns of nuclear and mitochondrial inheritance. Phase III examined the genetic relatedness of the different vegetative compatibility groups using a multilocus analysis approach. Heterokaryon formation was evident within and between vegetative compatibility groups. Observation of non-parental genotypes after heterokaryon formation confirmed that, although a rare event, horizontal genetic transfer occurred during heterokaryon formation. Uniparental mitochondria inheritance was observed in heterokaryons formed either by hyphal anastomosis or protoplast fusion. Drag resistance was expressed during heterokaryon formation, even across greater genetic distances than those distances imposed by vegetative compatibility. Phytogenies inferred from different molecular markers were incongruent at a significant level, challenging the clonal origins of Foe. Mating type genes were identified in this asexual pathogen Polymorphisms were detected within a Vegetative Compatibility Group (VCG) suggesting non-clonal inheritance and/or sexual recombination in Foe. This research was funded in part by a NIH-NIGMS (National Institutes of Health-National Institute of General Medical Sciences) Grant through the MBRS (Minority Biomedical Research Support), the Department of Biological Sciences and the Tropical Biology Program at FIU.
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Laaka-Lindberg, Sanna. "Ecology of asexual reproduction in hepatics /". Helsinki : Yliopistopaino, 2000. http://ethesis.helsinki.fi/julkaisut/mat/ekolo/vk/laaka-lindberg.
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Polak, Eline. "Asexual sporulation in the basidiomycete Coprinus cinereus /". [S.l.] : [s.n.], 1999. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=13125.
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Gingas, Vicki Marie. "Asexual embryogenesis and plant regeneration in Quercus /". The Ohio State University, 1988. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487588939088322.
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Anciaux, Yoann. "Dynamiques éco-évolutives en populations asexuées : sauvetage évolutif dans le paysage adaptatif de Fisher". Thesis, Montpellier, 2017. http://www.theses.fr/2017MONTT135/document.
Testo completoAbstract (sommario):
La capacité de persistance d’une population face à un changement environnemental stressant est une question complexe à l’interface entre l’écologie et l’évolution. Le processus par lequel une population échappe à l’extinction en s’adaptant aux nouvelles conditions environnementales stressantes est nommé sauvetage évolutif. Ce cas particulier de dynamique éco-évolutive est de plus en plus étudié autant théoriquement, qu’expérimentalement, entre autres dans le contexte des changements environnementaux d’origines anthropiques. Cependant, les études modélisant ce processus négligent les interactions entre génotypes et environnements impactant le potentiel évolutif des populations faisant aux changements environnementaux. Dans le cadre de cette thèse, j’ai développé des modèles intégrant ces interactions. Pour cela, j’ai modélisé le processus de sauvetage évolutif de populations à reproduction asexuée, face à des changements environnementaux abruptes, en utilisant le paysage adaptatif de Fisher (modèle géométrique de Fisher (1930)). Ce paysage nous a permis de modéliser ces interactions génotypes-environnement et leur impact sur la proportion de mutations pouvant sauver une population. A travers deux modèles, considérant soit le sauvetage d’une population par une mutation d’effet fort, soit par un grand nombre de mutations d’effets faibles, nous avons pu dégager des prédictions pour la probabilité de sauvetage évolutif en fonction des conditions environnementales et des caractéristiques de l’organisme étudié. Ces modèles peuvent être paramétrés sur des données d’évolution expérimentale et leurs prédictions comparées à des données de traitement antibiotiques visant des pathogènes asexués. Au-delà du sauvetage évolutif, les modèles développés nous ont également permis d’établir des outils permettant de modéliser d’autres dynamiques éco-évolutives, intégrant des interactions génotype-environnement et leurs effets sur la distribution d’effets des mutationsThe persistence ability of a population facing a stressing environmental change is a complex question at the connection between ecology and evolution. The process by which a population avoid extinction by adapting to the new stressing environmental conditions is termed evolutionary rescue. This particular case of eco-evolutionary dynamic is increasingly investigated both theoretically and experimentally, among other things in the context of the environmental changes from human activity. However, the studies modelling this process neglect the interactions between genotypes and environments impacting the evolutionary potential of the populations facing environmental changes. In the context of this thesis, I developed models integrating these interactions. To this end, I modelled the process of evolutionary rescue in asexual populations, facing abrupt environmental changes, using the adaptive landscape of Fisher (Fisher’s geometric model (1930)). This landscape allowed us to model the genotypes-environments interactions and their impact on the proportion of mutations able to save a population. Using two models, considering either the rescue of a population by a mutation of strong effect, either by a large number of mutation of small effect, we derived predictions for the probability of evolutionary rescue, which depends on the environmental conditions and the characteristics of the studied organism. These models can be parametrized on data from evolutionary experiments and their predictions compared to data of antibiotic treatments aiming on asexual pathogens. Beyond evolutionary rescue, the models developed in this thesis also gave tools to model other eco-evolutionary dynamics, integrating genotype-environment interactions and their effects on the distribution of mutations effects
Libri sul tema "Asexuel"
1
Rubt͡sova, Z. M. Ėvoli͡ut͡sionnoe znachenie apomiksisa: Istoriko-kriticheskoe issledovanie. Leningrad: "Nauka," Leningradskoe otd-nie, 1989.
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2
Rothblum, Esther D. Boston marriages: Romantic but asexual relationships among contemporary lesbians. Amherst: University of Massachusetts Press, 1993.
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3
Foster, Aasha. Measuring social invisibility and erasure: Development of the Asexual Microaggressions Scale. [New York, N.Y.?]: [publisher not identified], 2017.
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4
Phillips, Sarah Wynne. Asexual overwintering and morph determination in the lettuce root aphid Pemphigus bursarius (L.). Birmingham: University of Birmingham, 1999.
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5
Togashi, Tatsuya. The evolution of anisogamy: A fundamental phenomenon underlying sexual selection. New York: Cambridge University Press, 2011.
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6
Quist, Jeremy. Asexual. Mason Crest, 2022.
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Quist, Jeremy. Asexual. Mason Crest, 2022.
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Asexual Erotics. Columbus, OH: The Ohio State University Press, 2019.
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9
Asexual Pride. Independently Published, 2021.
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Schwerdtner, Hannes. Nope: 6x9 Asexual Pride Notizbuch Asexualität Tagebuch Regenbogen Bullet Journal Asexuell Notizblock LGBT Notizheft a Sexuell Logbuch. Independently Published, 2022.
Cerca il testo completoCapitoli di libri sul tema "Asexuel"
1
Hangay, George, Severiano F. Gayubo, Marjorie A. Hoy, Marta Goula, Allen Sanborn, Wendell L. Morrill, Gerd GÄde et al. "Asexual". In Encyclopedia of Entomology, 305. Dordrecht: Springer Netherlands, 2008. http://dx.doi.org/10.1007/978-1-4020-6359-6_10357.
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William Birky, C., e Timothy G. Barraclough. "Asexual Speciation". In Lost Sex, 201–16. Dordrecht: Springer Netherlands, 2009. http://dx.doi.org/10.1007/978-90-481-2770-2_10.
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3
Mehlhorn, Heinz. "Asexual Reproduction". In Encyclopedia of Parasitology, 234. Berlin, Heidelberg: Springer Berlin Heidelberg, 2016. http://dx.doi.org/10.1007/978-3-662-43978-4_3655.
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Mehlhorn, Heinz. "Asexual Reproduction". In Encyclopedia of Parasitology, 1. Berlin, Heidelberg: Springer Berlin Heidelberg, 2015. http://dx.doi.org/10.1007/978-3-642-27769-6_3655-1.
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Pandian, T. J. "Asexual Reproduction". In Reproduction and Development in Echinodermata and Prochordata, 94–135. Boca Raton, FL : CRC Press, Taylor & Francis Group, [2018] | Series: Reproduction and development in aquatic invertebrates ; volume 3 | “A science publishers book.”: CRC Press, 2018. http://dx.doi.org/10.1201/9780815364733-4.
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Edge, Jared. "Asexual Reproduction". In Encyclopedia of Animal Cognition and Behavior, 1–6. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-319-47829-6_325-1.
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Edge, Jared. "Asexual Reproduction". In Encyclopedia of Animal Cognition and Behavior, 481–86. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-319-55065-7_325.
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Simon, Kay A., Alyssa N. Clark e Ryan J. Watson. "Asexual Youth". In Encyclopedia of Adolescence, 1–6. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-319-32132-5_824-1.
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Kim, Eunjung. "Asexual Kinship". In Asexualities, 305–21. London: Routledge, 2024. http://dx.doi.org/10.4324/9781003178798-25.
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Jacobs, Joela, e Nicole Seymour. "Asexual Ecologies". In Asexualities, 23–36. London: Routledge, 2024. http://dx.doi.org/10.4324/9781003178798-4.
Testo completoAtti di convegni sul tema "Asexuel"
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Ahmadian, Sajad, e Ali Reza Khanteymoori. "Training back propagation neural networks using asexual reproduction optimization". In 2015 7th Conference on Information and Knowledge Technology (IKT). IEEE, 2015. http://dx.doi.org/10.1109/ikt.2015.7288738.
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2
Tongnunui, Prasert, Prasert Tongnunui, Woraporn Tarangkoon, Woraporn Tarangkoon, Parichat Hukiew, Parichat Hukiew, Patcharee Kaeoprakan et al. "SEAGRASS RESTORATION: AN UPDATE FROM TRANG PROVINCE, SOUTHWESTERN THAILAND". In Managing risks to coastal regions and communities in a changing world. Academus Publishing, 2017. http://dx.doi.org/10.31519/conferencearticle_5b1b9447ad58f1.23030316.
Testo completoAbstract (sommario):
Natural disasters may adversely affect coastal resources potentially leading to coastal habitat restorations that incorporate stakeholders and the general public. Appropriate methodologies for habitat restoration are developed to ensure the outcomes of this project. Currently, seagrass bed restoration by means of asexual and sexual propagation techniques have been used worldwide. However, the experience of seagrass (Enhalus acoroides) habitat restoration in Trang Province noted that to accomplish this project’s strategies involved the application of restoration techniques along with public and stakeholder participation. The application of asexual propagation, specifically the collection of single shoots from donor seagrasses and subsequent transplantation, is a convenient tool. However, from this project results, this process still has conceptual problems as from the large numbers of single shoots collected from donor seagrasses, the survival rate was relatively low. Furthermore, this process was complicated by conflicting interests between local communities near to the donor site and the project’s organizers. In order to reduce said conflicts, other techniques to balance stakeholder interests were instigated by this project, namely the development of both asexual and sexual propagation techniques. This project initiated a sexual propagation technique by the collection of wild seeds of Enhalus acoroides that were subsequently grown in the laboratory before natural habitat transplantation. This project results showed that seeds can be grown rapidly and can be cultured in large numbers. However, this development technique has a limit on rearing time because seedlings were found to be in decline after the third month of the experiment. These problems were compounded by a limiting factor that pushed the project’s organizers to decide to transplant seagrasses from the laboratory to the wild whether a time was seasonally suitable or unsuitable, the planting activity still done forward. This matter may have enhanced the low survival rate situation after seagrass transplantation to the wild. If there is a need to recover a seagrass bed, the above culture and transplantation methodologies should be used in conjunction with repeated periodic plantings until natural ecological function has been restored. In conclusion, further research should be instigated to improve the cultivation method for producing ready to plant seedlings and to improve methods of project operation.
3
Tongnunui, Prasert, Prasert Tongnunui, Woraporn Tarangkoon, Woraporn Tarangkoon, Parichat Hukiew, Parichat Hukiew, Patcharee Kaeoprakan et al. "SEAGRASS RESTORATION: AN UPDATE FROM TRANG PROVINCE, SOUTHWESTERN THAILAND". In Managing risks to coastal regions and communities in a changing world. Academus Publishing, 2017. http://dx.doi.org/10.21610/conferencearticle_58b431687e149.
Testo completoAbstract (sommario):
Natural disasters may adversely affect coastal resources potentially leading to coastal habitat restorations that incorporate stakeholders and the general public. Appropriate methodologies for habitat restoration are developed to ensure the outcomes of this project. Currently, seagrass bed restoration by means of asexual and sexual propagation techniques have been used worldwide. However, the experience of seagrass (Enhalus acoroides) habitat restoration in Trang Province noted that to accomplish this project’s strategies involved the application of restoration techniques along with public and stakeholder participation. The application of asexual propagation, specifically the collection of single shoots from donor seagrasses and subsequent transplantation, is a convenient tool. However, from this project results, this process still has conceptual problems as from the large numbers of single shoots collected from donor seagrasses, the survival rate was relatively low. Furthermore, this process was complicated by conflicting interests between local communities near to the donor site and the project’s organizers. In order to reduce said conflicts, other techniques to balance stakeholder interests were instigated by this project, namely the development of both asexual and sexual propagation techniques. This project initiated a sexual propagation technique by the collection of wild seeds of Enhalus acoroides that were subsequently grown in the laboratory before natural habitat transplantation. This project results showed that seeds can be grown rapidly and can be cultured in large numbers. However, this development technique has a limit on rearing time because seedlings were found to be in decline after the third month of the experiment. These problems were compounded by a limiting factor that pushed the project’s organizers to decide to transplant seagrasses from the laboratory to the wild whether a time was seasonally suitable or unsuitable, the planting activity still done forward. This matter may have enhanced the low survival rate situation after seagrass transplantation to the wild. If there is a need to recover a seagrass bed, the above culture and transplantation methodologies should be used in conjunction with repeated periodic plantings until natural ecological function has been restored. In conclusion, further research should be instigated to improve the cultivation method for producing ready to plant seedlings and to improve methods of project operation.
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Noei, Mohammadreza, e Mohammad Saniee Abadeh. "A Genetic Asexual Reproduction Optimization Algorithm for Imputing Missing Values". In 2019 9th International Conference on Computer and Knowledge Engineering (ICCKE). IEEE, 2019. http://dx.doi.org/10.1109/iccke48569.2019.8964808.
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"An asexual genetic algorithm for the smallholders’ demand selection problem". In The 9th International Food Operations and Processing Simulation Workshop. CAL-TEK srl, 2023. http://dx.doi.org/10.46354/i3m.2023.foodops.008.
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Jiao, Shuyun, Yanbo Wang e Ping Ao. "Dynamics of coexistence of asexual and sexual reproduction in adaptive landscape". In 2012 IEEE 6th International Conference on Systems Biology (ISB). IEEE, 2012. http://dx.doi.org/10.1109/isb.2012.6314135.
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Mahmoudi, Sina, Ebrahim Jelvehfard e Mohammad-Shahram Moin. "Evolutionary fractal image compression using asexual reproduction optimization with guided mutation". In 2013 8th Iranian Conference on Machine Vision and Image Processing (MVIP). IEEE, 2013. http://dx.doi.org/10.1109/iranianmvip.2013.6780022.
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Ross, R., e R. Hall. "A FPGA Simulation Using Asexual Genetic Algorithms for Integrated Self-Repair". In First NASA/ESA Conference on Adaptive Hardware and Systems (AHS'06). IEEE, 2006. http://dx.doi.org/10.1109/ahs.2006.3.
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Hashemi, Seyyed Mohammad R., Ehsan Kozegar, Mohammad Mahdi Deramgozin e Behrouz Minaei-Bidgoli. "Training Feed-forward Neural Networks using Asexual Reproduction Optimization (ARO) Algorithm". In 2019 5th Conference on Knowledge Based Engineering and Innovation (KBEI). IEEE, 2019. http://dx.doi.org/10.1109/kbei.2019.8735035.
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Yalong, Zhang, Hao Yongjun, Li Hongye, Chen Peng, Lian Chengbin e Bao Xuan. "Global Path Planning of Unmanned Underwater Vehicle with Asexual Reproduction Optimization". In 2023 IEEE 11th International Conference on Computer Science and Network Technology (ICCSNT). IEEE, 2023. http://dx.doi.org/10.1109/iccsnt58790.2023.10334570.
Testo completoRapporti di organizzazioni sul tema "Asexuel"
1
Gazit, Shmuel, e Robert Knight, Jr. Asexual Embryogenesis in the Mango (Mangifera indica L). United States Department of Agriculture, febbraio 1989. http://dx.doi.org/10.32747/1989.7593408.bard.
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2
Bell, Alexa. Romantic Identity and LGBTQ Identification: Variations of Experience in the Asexual Community. Portland State University Library, gennaio 2015. http://dx.doi.org/10.15760/honors.159.
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3
Rochel Ortega, Elizabeth, Jefersson Andrés Rodríguez Blandón, Pedro David Suárez Villota e Jorge Andrés Castillo. Taxonomía y material genético: propagación de material vegetal. Corporación colombiana de investigación agropecuaria - AGROSAVIA, 2021. http://dx.doi.org/10.21930/agrosavia.infografia.2021.26.
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Tippery, Nicholas, Nathan Harms, Matthew Purcell, Sun Lee Hong, Patrick Häfliger, Katelin Killoy, Ashley Wolfe e Ryan Thum. Assessing the genetic diversity of Nymphoides peltata in the native and adventive range using microsatellite markers. Engineer Research and Development Center (U.S.), febbraio 2024. http://dx.doi.org/10.21079/11681/48222.
Testo completoAbstract (sommario):
Nymphoides peltata (yellow floatingheart), native to Eurasia, is an invasive plant in the USA, where it grows in relatively isolated but widespread populations. The species is capable of sexual reproduction by seed and asexual reproduction through fragmentation. Although N. peltata is recognized as a noxious weed, little is known about its geographic region of origin or its dispersal mechanisms and relative amount of genetic variation in its adventive range. We conducted a genetic analysis of N. peltata by studying 68 localities across the native range and 47 localities in the adventive range, using microsatellite markers to determine genetic variability within and among populations, and to infer regions in the native range from which invasive plants originated. A large number of sites in the USA were genetically identical to one another, and there were two predominant multilocus allele phenotypes that were distributed in the northern and southern latitudes, respectively. Additional USA sites were similar to one of the predominant genetic profiles, with greater genetic diversity in southern populations. The genetically identical sites are consistent with asexual spread, potentially via anthropogenic mechanisms. Plants across the USA range were observed to produce viable seeds, and some genetic variation could be explained by sexual reproduction. All USA plants were more similar to plants in Europe than they were to plants in Asia, indicating that the plants likely were introduced originally from Europe. The existence of two genetic clusters and their similarity to plants in different parts of Europe constitute evidence for at least two N. peltata introductions into the USA.
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Cothron, Annaliese, Don Clermont, Amber Shaver, Elizabeth Alpert e Chukwuebuka Ogwo. Improving Knowledge, Comfort, and Attitudes for LGBTQIA+ Clinical Care and Dental Education. American Institute of Dental Public Health, 2023. http://dx.doi.org/10.58677/tvin3595.
Testo completoAbstract (sommario):
Oral health does not exist in a silo. The mouth-body connection is a biological aspect of physical wellbeing that exists alongside the social and political drivers of whole-person health. Lesbian, gay, bisexual, transgender, queer, intersex, and agender/ asexual people, and people of other marginalized gender or sexual identities (LGBTQIA+), have experienced historical exclusion from healthcare systems perpetuated by chronic stigma. Ongoing discrimination, cultural insensitivity, and blatant homophobia/transphobia among healthcare staff results in poor health outcomes, including oral health. These exchanges either facilitate or inhibit respectful, high-quality, patient-centered care cognizant of intersectionality. In 2022, the American Institute of Dental Public Health (AIDPH) disseminated a mixed-methods survey to just over 200 oral health professionals to assess knowledge, attitudes, and practices regarding LGBTQIA+ oral health.
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Emmanuel A. Abesamis, Luis, e Tabitha Hrynick. LGBTQIA+-inclusive humanitarian action in the Philippines. Institute of Development Studies, settembre 2024. http://dx.doi.org/10.19088/sshap.2024.041.
Testo completoAbstract (sommario):
Humanitarian crises affect diverse populations in complex ways, often exacerbating pre-existing vulnerabilities and inequalities. Among those disproportionately impacted are LGBTQIA+ (lesbian, gay, bisexual, transgender, queer, intersex, asexual and other SOGIESC – sexual orientations, gender identities, and sex characteristics) individuals and communities. In the Philippines – a country that frequently experiences humanitarian emergencies, such as pandemics, conflict, and environmental hazards – LGBTQIA+ people face unique challenges. Both LGBTQIA+ people and the challenges they face are often overlooked in humanitarian action – from the planning stage to the implementation and evaluation of initiatives This SSHAP Brief aims to provide local and regional non-governmental organisations (NGOs) and others involved in development and humanitarian programming in the Philippines with key considerations for addressing the complex needs of LGBTQIA+ people in humanitarian contexts. It seeks to support humanitarian actors to design and implement more effective, equitable and inclusive activities. To this end, the brief examines the social, economic and legal landscape for LGBTQIA+ groups, exploring their specific capacities and vulnerabilities during crises and offering practical guidance. Drawing on academic and grey literature and consultations with academic, humanitarian and community experts, this brief also bridges a gap between short-term crisis response and long-term transformational change. This brief emphasises the importance of LGBTQIA+ inclusion across all phases of humanitarian action. Ultimately, it aims to contribute to building more resilient LGBTQIA+ communities and a more inclusive humanitarian sector in the Philippines.
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Ohad, Nir, e Robert Fischer. Control of Fertilization-Independent Development by the FIE1 Gene. United States Department of Agriculture, agosto 2000. http://dx.doi.org/10.32747/2000.7575290.bard.
Testo completoAbstract (sommario):
A fundamental problem in biology is to understand how fertilization initiates reproductive development. During plant reproduction, one sperm cell fuses with the egg to form an embryo, whereas a second sperm cell fuses with the adjacent central cell nucleus to form the endosperm tissue that supports embryo and/or seedling development. To understand the mechanisms that initiate reproduction, we have isolated mutants of Arabidopsis that allow for replication of the central cell and subsequent endosperm development without fertilization. In this project we have cloned the MEA gene and showed that it encode a SET- domain polycomb protein. Such proteins are known to form chromatin-protein complexes that repress homeotic gene transcription and influence cell proliferation from Drosophylla to mammals. We propose a model whereby MEA and an additional polycomb protein we have cloned, FIE , function to suppress a critical aspect of early plant reproduction and endosperm development, until fertilization occurs. Using a molecular approach we were able to determine that FIE and MEA interact physically, suggesting that these proteins have been conserved also during the evolution of flowering plants. The analysis of MEA expression pattern revealed that it is an imprinted gene that displays parent-of- origin-dependent monoallelic expression specifically in the endosperm tissue. Silencing of the paternal MEA allele in the endosperm and the phenotype of mutant mea seeds support the parental conflict theory for the evolution of imprinting in plants and mammals. These results contribute new information on the initiation of endosperm development and provide a unique entry point to study asexual reproduction and apomixis which is expected to improve crop production.
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Sherman, A., D. N. Kuhn, Y. Cohen, R. Ophir e R. Goenaga. Exploring the polyembryonic seed trait in mango as a basis for a biotechnology platform for fruit tree crops. Israel: United States-Israel Binational Agricultural Research and Development Fund, 2021. http://dx.doi.org/10.32747/2021.8134176.bard.
Testo completoAbstract (sommario):
Mango is one of the most important fruit crops. However, the biology of this fruit tree is under studied. The lack of genetic and genomic resources has limited progress in mango research and breeding. Several research groups have recently started developing genomic tools for mango by creating transcriptome and genomic data. Sexual reproduction in plants is the main pathway for the creation of new genetic combinations. In modern agriculture, breeders exploit the genetic diversity generated through sexual reproduction to develop elite cultivars; however, these cultivars require genetic stabilization before they are suitable for mass propagation for uniform crop production. In heterozygous plants such as fruit trees, vegetative propagation (cloning) is the primary path for the propagation of genetically uniform plants. Another natural plant mechanism that can create genetically uniform plants (clones) is apomixes. Apomixis is defined as asexual reproduction through seeds that lead to the production of clonal progeny whose genotype is identical to that of the mother plant. In fruit crops like citrus and mango, sporophytic apomixes result in polyembryony, where seeds contain multiple embryos, one of which is sexually originated, and the others are clones of the mother tree. As part of this research, the reference genome of mango was established as a basic platform for mango breeding and research. It was used to map two important mango traits fruit size and polyembryony. The draft genome 'Tommy Atkins' sequence was generated using NRGene de-novo Magic on high molecular weight DNA of 'Tommy Atkins,' supplemented by 10X Genomics long read sequencing to improve the initial assembly. The final 'Tommy Atkins' genome assembly was a consensus sequence that included 20 pseudomolecules representing the 20 chromosomes of mango. The availability of a genome enables the genetic dissection of important traits. We demonstrated the utility of the genome assembly and the 'Tommy Atkins' x 'Kensington Pride' map by analyzing fruit weight phenotypic data and identifying two QTLs for this trait.
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Israel, Alvaro, e John Merrill. Production of Seed Stocks for Sustainable Tank Cultivation of the Red Edible Seaweed Porphyra. United States Department of Agriculture, 2006. http://dx.doi.org/10.32747/2006.7696527.bard.
Testo completoAbstract (sommario):
Porphyra species (commonly known as ‘nori’ or ‘purple laver’) are edible red seaweeds rich in proteins, vitamins and other highly valued biogenic compounds. For years Porphyra has been cultured using seeded nets extended in the open sea, and its biomass consumed primarily in the Far East. While demands for international markets have increased steadily at an average of 20% per year, supplies are on the verge and not expected to meet future demands. Alternatively, land-based cultivation of seaweed has become attractive in the mariculture industry since (1) important growth parameters can be controlled, (2) is environmentally friendly and (3) perfectly matches with integrated aquaculture leading to sustainable, high quality products. During the last few years a tank cultivation technology for Porphyra has been developed at the Israeli institution. This technology is based on indoor production of asexual spores and their subsequent growth to 1-2 mm seedlings. The seedlings are then transferred to outdoor tanks and ponds when seawater temperatures drop to 20 °C, or below, and days become shorter during winter time. However, the current technology efficiently serves only about 100 m2 of ponds during one growth season. In order to produce seedlings in sufficient amounts, it is critical to address both technical and biological aspects of seedling production, securing optimal up-scale to commercial-size cultivation farms. We hypothesize that massive production of spores is related to thalli origin, thalli age and sporulation triggers, and that seedling survival and their subsequent growth potential is determined by the seawater quality and overall indoor growth conditions imposed. A series of bio-reactors were constructed and tested in which spore release and spore growth were separately studied. The main assessment criteria for optimal viability of the seedlings will be by determining their electron transport rate using PAM fluorometry and by subsequent growth and biomass yields in outdoor ponds. Altogether the project showed (1), controlled sporulation is possible in big outdoor/growth chamber settings provided initial stock material (small frozen seedlings) is at hand, (2), contamination problems can be almost completely avoided if stock material is properly handled (clean as possible and partially dehydrated prior to freezing), (3), spore release can significantly be enhance using high nutrient levels during thawing for P. yezoensis and P. haitanensis, but not for P. rosengurttii, (4), PAM fluorometry is an efficient tool to estimate growth capacity in both seedlings and juvenile thalli. The BARD funding also served to explore other aspects of Porphyra biology and cultivation. For example, the taxonomical status of Porphyra strains used in this study was defined (see appendix), and the potential use of this seaweed in bioremediation was well substantiated. In addition, BARD funding supported a number of opportunities and activities in the Israeli lab, direct or indirectly related to the initial objectives of the project such as: additional molecular work in other seaweeds, description of at least 2 new species for the Israeli Mediterranean, and continuous support for the writing of a book on Global Change and applied aspects of seaweeds. The technology for Porphyra cultivation in land-based ponds is readily available. This study corroborated previous know-how of Porphyra growth in tanks and ponds, and yet offers important improvements regarding seedling production and their handling for successful cultivation. This study supported various other activities opening additional important issues in the biology/cultivation/use of Porphyra and other seaweeds.
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Horwitz, Benjamin A., e Barbara Gillian Turgeon. Fungal Iron Acquisition, Oxidative Stress and Virulence in the Cochliobolus-maize Interaction. United States Department of Agriculture, marzo 2012. http://dx.doi.org/10.32747/2012.7709885.bard.
Testo completoAbstract (sommario):
Our project focused on genes for high affinity iron acquisition in Cochliobolus heterostrophus, a necrotrophic pathogen of maize, and their intertwined relationship to oxidative stress status and virulence of the fungus on the host. An intriguing question was why mutants lacking the nonribosomal peptide synthetase (NRPS) gene (NPS6) responsible for synthesis of the extracellular siderophore, coprogen, are sensitive to oxidative stress. Our overall objective was to understand the mechanistic connection between iron stress and oxidative stress as related to virulence of a plant pathogen to its host. The first objective was to examine the interface where small molecule peptide and reactive oxygen species (ROS) mechanisms overlap. The second objective was to determine if the molecular explanation for common function is common signal transduction pathways. These pathways, built around sensor kinases, response regulators, and transcription factors may link sequestering of iron, production of antioxidants, resistance to oxidative stress, and virulence. We tested these hypotheses by genetic manipulation of the pathogen, virulence assays on the host plant, and by following the expression of key fungal genes. An addition to the original program, made in the first year, was to develop, for fungi, a genetically encoded indicator of redox state based on the commercially available Gfp-based probe pHyper, designed for animal cell biology. We implemented several tools including a genetically encoded indicator of redox state, a procedure to grow iron-depleted plants, and constructed a number of new mutants in regulatory genes. Lack of the major Fe acquisition pathways results in an almost completely avirulent phenotype, showing how critical Fe acquisition is for the pathogen to cause disease. Mutants in conserved signaling pathways have normal ability to regulate NPS6 in response to Fe levels, as do mutants in Lae1 and Vel1, two master regulators of gene expression. Vel1 mutants are sensitive to oxidative stress, and the reason may be underexpression of a catalase gene. In nps6 mutants, CAT3 is also underexpressed, perhaps explaining the sensitivity to oxidative stress. We constructed a deletion mutant for the Fe sensor-regulator SreA and found that it is required for down regulation of NPS6 under Fe-replete conditions. Lack of SreA, though, did not make the fungus over-sensitive to ROS, though the mutant had a slow growth rate. This suggests that overproduction of siderophore under Fe-replete conditions is not very damaging. On the other hand, increasing Fe levels protected nps6 mutants from inhibition by ROS, implying that Fe-catalyzed Fenton reactions are not the main factor in its sensitivity to ROS. We have made some progress in understanding why siderophore mutants are sensitive to oxidative stress, and in doing so, defined some novel regulatory relationships. Catalase genes, which are not directly related to siderophore biosynthesis, are underexpressed in nps6 mutants, suggesting that the siderophore product (with or without bound Fe) may act as a signal. Siderophores, therefore, could be a target for intervention in the field, either by supplying an incorrect signal or blocking a signal normally provided during infection. We already know that nps6 mutants cause smaller lesions and have difficulty establishing invasive growth in the host. Lae1 and Vel1 are the first factors shown to regulate both super virulence conferred by T-toxin, and basic pathogenicity, due to unknown factors. The mutants are also altered in oxidative stress responses, key to success in the infection court, asexual and sexual development, essential for fungal dissemination in the field, aerial hyphal growth, and pigment biosynthesis, essential for survival in the field. Mutants in genes encoding NADPH oxidase (Nox) are compromised in development and virulence. Indeed the triple mutant, which should lack all Nox activity, was nearly avirulent. Again, gene expression experiments provided us with initial evidence that superoxide produced by the fungus may be most important as a signal. Blocking oxidant production by the pathogen may be a way to protect the plant host, in interactions with necrotrophs such as C. heterostrophus which seem to thrive in an oxidant environment.