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Karel Janko - One of the best experts on this subject based on the ideXlab platform.
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hybrid Asexuality as a primary postzygotic barrier between nascent species on the interconnection between Asexuality hybridization and speciation
Molecular Ecology, 2018Co-Authors: Karel Janko, Jan Paces, Hilde Wilkinsonherbots, Rui Costa, Jan Roslein, Pavel Drozd, Nataliia IakovenkoAbstract:Although sexual reproduction is ubiquitous throughout nature, the molecular machinery behind it has been repeatedly disrupted during evolution, leading to the emergence of asexual lineages in all eukaryotic phyla. Despite intensive research, little is known about what causes the switch from sexual reproduction to Asexuality. Interspecific hybridization is one of the candidate explanations but the reasons for the apparent association between hybridization and Asexuality remain unclear. In this study we combined cross-breeding experiments with population genetic and phylogenomic approaches to reveal the history of speciation and Asexuality evolution in European spined loaches (Cobitis). Contemporary species readily hybridize in hybrid zones, but produce infertile males and fertile but clonally reproducing females that cannot mediate introgressions. However, our analysis of exome data indicates that intensive gene flow between species has occurred in the past. Crossings among species with various genetic distances showed that, while distantly related species produced asexual females and sterile males, closely related species produce sexually reproducing hybrids of both sexes. Our results suggest that hybridization leads to sexual hybrids at the initial stages of speciation, but as the species diverge further, the gradual accumulation of reproductive incompatibilities between species could distort their gametogenesis towards Asexuality. Interestingly, comparative analysis of published data revealed that hybrid Asexuality generally evolves at lower genetic divergences than hybrid sterility or inviability. Given that hybrid Asexuality effectively restricts gene flow, it may establish a primary reproductive barrier earlier during diversification than other ‘classical’ forms of postzygotic incompatibilities. Hybrid Asexuality may thus indirectly contribute to the speciation process. This article is protected by copyright. All rights reserved.
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asexual reproduction does not apparently increase the rate of chromosomal evolution karyotype stability in diploid and triploid clonal hybrid fish cobitis cypriniformes teleostei
PLOS ONE, 2016Co-Authors: Zuzana Majtanova, Lukas Choleva, Radka Symonova, Petr Rab, Jan Kotusz, Ladislav Pekarik, Karel JankoAbstract:Interspecific hybridization, polyploidization and transitions from sexuality to Asexuality considerably affect organismal genomes. Especially the last mentioned process has been assumed to play a significant role in the initiation of chromosomal rearrangements, causing increased rates of karyotype evolution. We used cytogenetic analysis and molecular dating of cladogenetic events to compare the rate of changes of chromosome morphology and karyotype in asexually and sexually reproducing counterparts in European spined loach fish (Cobitis). We studied metaphases of three sexually reproducing species and their diploid and polyploid hybrid clones of different age of origin. The material includes artificial F1 hybrid strains, representatives of lineage originated in Holocene epoch, and also individuals of an oldest known age to date (roughly 0.37 MYA). Thereafter we applied GISH technique as a marker to differentiate parental chromosomal sets in hybrids. Although the sexual species accumulated remarkable chromosomal rearrangements after their speciation, we observed no differences in chromosome numbers and/or morphology among karyotypes of asexual hybrids. These hybrids possess chromosome sets originating from respective parental species with no cytogenetically detectable recombinations, suggesting their integrity even in a long term. The switch to asexual reproduction thus did not provoke any significant acceleration of the rate of chromosomal evolution in Cobitis. Asexual animals described in other case studies reproduce ameiotically, while Cobitis hybrids described here produce eggs likely through modified meiosis. Therefore, our findings indicate that the effect of Asexuality on the rate of chromosomal change may be context-dependent rather than universal and related to particular type of asexual reproduction.
Nataliia Iakovenko - One of the best experts on this subject based on the ideXlab platform.
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hybrid Asexuality as a primary postzygotic barrier between nascent species on the interconnection between Asexuality hybridization and speciation
Molecular Ecology, 2018Co-Authors: Karel Janko, Jan Paces, Hilde Wilkinsonherbots, Rui Costa, Jan Roslein, Pavel Drozd, Nataliia IakovenkoAbstract:Although sexual reproduction is ubiquitous throughout nature, the molecular machinery behind it has been repeatedly disrupted during evolution, leading to the emergence of asexual lineages in all eukaryotic phyla. Despite intensive research, little is known about what causes the switch from sexual reproduction to Asexuality. Interspecific hybridization is one of the candidate explanations but the reasons for the apparent association between hybridization and Asexuality remain unclear. In this study we combined cross-breeding experiments with population genetic and phylogenomic approaches to reveal the history of speciation and Asexuality evolution in European spined loaches (Cobitis). Contemporary species readily hybridize in hybrid zones, but produce infertile males and fertile but clonally reproducing females that cannot mediate introgressions. However, our analysis of exome data indicates that intensive gene flow between species has occurred in the past. Crossings among species with various genetic distances showed that, while distantly related species produced asexual females and sterile males, closely related species produce sexually reproducing hybrids of both sexes. Our results suggest that hybridization leads to sexual hybrids at the initial stages of speciation, but as the species diverge further, the gradual accumulation of reproductive incompatibilities between species could distort their gametogenesis towards Asexuality. Interestingly, comparative analysis of published data revealed that hybrid Asexuality generally evolves at lower genetic divergences than hybrid sterility or inviability. Given that hybrid Asexuality effectively restricts gene flow, it may establish a primary reproductive barrier earlier during diversification than other ‘classical’ forms of postzygotic incompatibilities. Hybrid Asexuality may thus indirectly contribute to the speciation process. This article is protected by copyright. All rights reserved.
Anthony F Bogaert - One of the best experts on this subject based on the ideXlab platform.
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Asexuality what it is and why it matters
Journal of Sex Research, 2015Co-Authors: Anthony F BogaertAbstract:In this review article, human Asexuality, a relatively understudied phenomenon, is discussed. Specifically, definitions and conceptualizations of Asexuality (e.g., is it a unique category of sexual orientation?), biological and historical contexts, identity issues, discrimination against asexual people relative to other minorities, origins, and variations, including gender differences, are reviewed. Whether Asexuality should be construed as a disorder is also discussed. The study of Asexuality allows for a better understanding of an underrecognized sexual minority but also affords a unique opportunity to examine and better understand human sexuality.
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the demography of Asexuality
2013Co-Authors: Anthony F BogaertAbstract:Asexuality has begun to receive both academic (e.g., Bogaert 2004, 2006a, 2008; Prause and Graham 2007; Brotto et al. 2010; Poston and Baumle 2010) and public (e.g., New Scientist; Pagan Westfall 2004) attention. Why does the study of Asexuality matter, aside from the scientific and public curiosity about a sexual minority that has been overlooked until recently? A person’s sexuality, particularly as basic as whether he or she is asexual or not, may play a profound role in their social circumstances and life choices, including whether they marry or not, whether they have children or not, and their mental and physical health (e.g., atypical hormonal profile; lower STI risk, etc.). Thus, the study of Asexuality is relevant to a number of demographic issues such as health, marriage, and fertility.
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Asexuality and autochorissexualism identity less sexuality
Archives of Sexual Behavior, 2012Co-Authors: Anthony F BogaertAbstract:I present evidence that target-oriented paraphilias may occur in some who report no sexual attraction for others or those who identify as asexual. One target-oriented paraphilia in some asexual people is a disconnection between their identity and a sexual target/object. I name this phenomenon autochorissexualism or “identity-less” sexuality.
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toward a conceptual understanding of Asexuality
Review of General Psychology, 2006Co-Authors: Anthony F BogaertAbstract:Asexuality has been the subject of recent academic (A. F. Bogaert, 2004) and public (e.g., New Scientist; CNN) discourse. This has raised questions about the conceptualization and definition of Asexuality. Here the author reviews some of these issues, discusses Asexuality from a sexual orientation point of view (i.e., as a lack of sexual attraction), and reviews the similarities and differences between this definition and related phenomena (e.g., hypoactive sexual desire disorder). Finally, the author concludes that the term Asexuality should not necessarily be used to describe a pathological or health-compromised state.
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Asexuality prevalence and associated factors in a national probability sample
Journal of Sex Research, 2004Co-Authors: Anthony F BogaertAbstract:I used data from a national probability sample (N > 18,000) of British residents to investigate Asexuality, defined as having no sexual attraction to a partner of either sex. Approximately 1% (n = 195) of the sample indicated they were asexual. A number of factors were related to Asexuality, including gender (i.e., more women than men), short stature, low education, low socioeconomic status, and poor health. Asexual women also had a later onset of menarche relative to sexual women. The results suggest that a number of pathways, both biological and psychosocial, contribute to the development of Asexuality.
Tanja Schwander - One of the best experts on this subject based on the ideXlab platform.
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evolution of Asexuality via different mechanisms in grass thrips thysanoptera aptinothrips
Evolution, 2014Co-Authors: Casper J Van Der Kooi, Tanja SchwanderAbstract:Asexual lineages can derive from sexual ancestors via different mechanisms and at variable rates, which affects the diversity of the asexual population and thereby its ecological success. We investigated the variation and evolution of reproductive systems in Aptinothrips, a genus of grass thrips comprising four species. Extensive population surveys and breeding experiments indicated sexual reproduction in A. elegans, Asexuality in A. stylifer and A. karnyi, and both sexual and asexual lineages in A. rufus. Asexuality in A. stylifer and A. rufus coincides with a worldwide distribution, with sexual A. rufus lineages confined to a limited area. Inference of molecular phylogenies and antibiotic treatment revealed different causes of Asexuality in different species. Asexuality in A. stylifer and A. karnyi has most likely genetic causes, while it is induced by endosymbionts in A. rufus. Endosymbiont-community characterization revealed presence of Wolbachia, and lack of other bacteria known to manipulate host reproduction. However, only 69% asexual A. rufus females are Wolbachia-infected, indicating that either an undescribed endosymbiont causes Asexuality in this species or that Wolbachia was lost in several lineages that remained asexual. These results open new perspectives for studies on the maintenance of mixed sexual and asexual reproduction in natural populations.
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Genetic causes of transitions from sexual reproduction to Asexuality in plants and animals
Journal of evolutionary biology, 2014Co-Authors: Maurine Neiman, Timothy F. Sharbel, Tanja SchwanderAbstract:The persistence of sexual reproduction in the face of competition from asexual invaders is more likely if asexual lineages are produced infrequently or have low fitness. The generation rate and success of new asexual lineages will be influenced by the proximate mechanisms underlying transitions to Asexuality. As such, characterization of these mechanisms can help explain the distribution of reproductive modes among natural populations. Here, we synthesize the literature addressing proximate causes of transitions from sexual to asexual reproduction in plants and animals. In cyclical and facultatively asexual taxa, individual mutations can cause obligate Asexuality. The evolution of Asexuality in obligately sexual groups is more complex, requiring the simultaneous acquisition of two traits generally controlled by different genetic factors: unreduced gamete formation and spontaneous development of unfertilized gametes. At least three ‘pre-adaptations’ could favour transitions to obligate Asexuality in obligate sexuals. First, linkage among loci affecting separate key components of Asexuality facilitates its spread, with evidence for these linkage blocks in plants. Second, Asexuality should evolve more readily in haplodiploids; support for this hypothesis comes from two examples where a single locus causes transitions to Asexuality. Third, standing genetic variation for the production of unreduced gametes could facilitate transitions to Asexuality, but whether the ability to produce unreduced gametes contributes to the evolution of obligate Asexuality remains unclear. We close by reviewing the associations between Asexuality, hybridization and polyploidy, and argue that current data suggest that hybridization is more likely to play a causal role in transitions to Asexuality than polyploidy.
Lori A Brotto - One of the best experts on this subject based on the ideXlab platform.
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Asexuality sexual orientation paraphilia sexual dysfunction or none of the above
Archives of Sexual Behavior, 2017Co-Authors: Lori A Brotto, Morag A YuleAbstract:Although lack of sexual attraction was first quantified by Kinsey, large-scale and systematic research on the prevalence and correlates of Asexuality has only emerged over the past decade. Several theories have been posited to account for the nature of Asexuality. The goal of this review was to consider the evidence for whether Asexuality is best classified as a psychiatric syndrome (or a symptom of one), a sexual dysfunction, or a paraphilia. Based on the available science, we believe there is not sufficient evidence to support the categorization of Asexuality as a psychiatric condition (or symptom of one) or as a disorder of sexual desire. There is some evidence that a subset of self-identified asexuals have a paraphilia. We also considered evidence supporting the classification of Asexuality as a unique sexual orientation. We conclude that Asexuality is a heterogeneous entity that likely meets conditions for a sexual orientation, and that researchers should further explore evidence for such a categorization.
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human Asexuality what do we know about a lack of sexual attraction
Current Sexual Health Reports, 2017Co-Authors: Morag A Yule, Lori A Brotto, Boris B GorzalkaAbstract:This paper reviews the recent literature on human Asexuality, which is generally defined as an absence of sexual attraction. Recent work has focused on exploring whether Asexuality is best conceptualized as a mental health difficulty, a sexual dysfunction, a paraphilia, a sexual orientation, or as an identity/community, and this literature is reviewed. The authors conclude that Asexuality may best be thought of as a sexual orientation and that Asexuality as an identity and a community is an important component of the asexual experience. Overall, the term Asexuality likely describes a heterogeneous group of individuals, with a range of experiences. Asexuality is likely a normal variation in the experience of human sexuality, and future research into Asexuality might inform our understanding of sexuality in general.
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a validated measure of no sexual attraction the Asexuality identification scale
Psychological Assessment, 2015Co-Authors: Morag A Yule, Lori A Brotto, Boris B GorzalkaAbstract:Human Asexuality has been described as a lack of sexual attraction toward anyone or anything. One percent of the adult population is thought to be asexual, and research suggests that Asexuality is best conceptualized as a sexual orientation. A serious limitation in past research on Asexuality has been the complete lack of a validated tool to measure Asexuality. Due to limitations in recruiting sufficiently powered local samples, most studies have relied on recruiting via online web-based asexual communities. This is problematic because it limits the sample to individuals who have been recruited through established Asexuality networks/communities. The present study aimed to develop and validate a self-report questionnaire to assess Asexuality. The questionnaire was intended to provide a valid measure independent of whether the individual self-identified as asexual and was developed in several stages, including: development and administration of open-ended questions (209 participants: 139 asexual and 70 sexual); administration and analysis of resulting 111 items (917 participants: 165 asexual and 752 sexual); administration and analysis of 37 retained items (1,242 participants: 316 asexual and 926 sexual); and validity analysis of the final items. The resulting Asexuality Identification Scale (AIS), a 12-item questionnaire, is a brief, valid, and reliable self-report instrument for assessing Asexuality. It is psychometrically sound, easy to administer, and has demonstrated ability to discriminate between sexual and asexual individuals. It should prove useful to allow researchers to recruit more representative samples of the asexual population, permitting for an increased understanding of Asexuality.
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Asexuality: A Mixed-Methods Approach
Archives of Sexual Behavior, 2010Co-Authors: Lori A Brotto, Gail Knudson, Jess Inskip, Katherine Rhodes, Yvonne ErskineAbstract:Current definitions of Asexuality focus on sexual attraction, sexual behavior, and lack of sexual orientation or sexual excitation; however, the extent to which these definitions are accepted by self-identified asexuals is unknown. The goal of Study 1 was to examine relationship characteristics, frequency of sexual behaviors, sexual difficulties and distress, psychopathology, interpersonal functioning, and alexithymia in 187 asexuals recruited from the Asexuality Visibility and Education Network (AVEN). Asexual men ( n = 54) and women ( n = 133) completed validated questionnaires online. Sexual response was lower than normative data and was not experienced as distressing, and masturbation frequency in males was similar to available data for sexual men. Social withdrawal was the most elevated personality subscale; however, interpersonal functioning was in the normal range. Alexithymia was elevated in 12%. Social desirability was also in the normal range. Study 2 was designed to expand upon these quantitative findings with 15 asexuals from Study 1 through in-depth telephone interviews. The findings suggest that Asexuality is best conceptualized as a lack of sexual attraction; however, asexuals varied greatly in their experience of sexual response and behavior. Asexuals partnered with sexuals acknowledged having to “negotiate” sexual activity. There were not higher rates of psychopathology among asexuals; however, a subset might fit the criteria for Schizoid Personality Disorder. There was also strong opposition to viewing Asexuality as an extreme case of sexual desire disorder. Finally, asexuals were very motivated to liaise with sex researchers to further the scientific study of Asexuality.
