Journal articles on the topic 'Asexual'
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1
Key, Adam. "The Silent A." Journal of Autoethnography 2, no. 4 (2021): 446–65. http://dx.doi.org/10.1525/joae.2021.2.4.446.
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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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Auld, Stuart K. J. R., Shona K. Tinkler, and Matthew C. Tinsley. "Sex as a strategy against rapidly evolving parasites." Proceedings of the Royal Society B: Biological Sciences 283, no. 1845 (December 28, 2016): 20162226. http://dx.doi.org/10.1098/rspb.2016.2226.
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Why is sex ubiquitous when asexual reproduction is much less costly? Sex disrupts coadapted gene complexes; it also causes costs associated with mate finding and the production of males who do not themselves bear offspring. Theory predicts parasites select for host sex, because genetically variable offspring can escape infection from parasites adapted to infect the previous generations. We examine this using a facultative sexual crustacean, Daphnia magna, and its sterilizing bacterial parasite, Pasteuria ramosa . We obtained sexually and asexually produced offspring from wild-caught hosts and exposed them to contemporary parasites or parasites isolated from the same population one year later. We found rapid parasite adaptation to replicate within asexual but not sexual offspring. Moreover, sexually produced offspring were twice as resistant to infection as asexuals when exposed to parasites that had coevolved alongside their parents (i.e. the year two parasite). This fulfils the requirement that the benefits of sex must be both large and rapid for sex to be favoured by selection.
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Tobler, M., and I. Schlupp. "Expanding the horizon: the Red Queen and potential alternatives." Canadian Journal of Zoology 86, no. 8 (August 2008): 765–73. http://dx.doi.org/10.1139/z08-056.
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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., and B. Drossel. "Sexual reproduction prevails in a world of structured resources in short supply." Proceedings of the Royal Society B: Biological Sciences 274, no. 1614 (February 27, 2007): 1225–31. http://dx.doi.org/10.1098/rspb.2007.0040.
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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, and Tanja Schwander. "Fundamental and realized feeding niche breadths of sexual and asexual stick insects." Proceedings of the Royal Society B: Biological Sciences 285, no. 1892 (November 28, 2018): 20181805. http://dx.doi.org/10.1098/rspb.2018.1805.
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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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Thomsen, Erik, and Eckart Håkansson. "Sexual versus asexual dispersal in clonal animals: examples from cheilostome bryozoans." Paleobiology 21, no. 4 (1995): 496–508. http://dx.doi.org/10.1017/s0094837300013506.
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The relative numbers of sexually and asexually recruited colonies and the proportion of brooding zooids were determined in 26 species of cheilostome bryozoans of Late Cretaceous and Early Tertiary ages. Asexual reproduction seems to be much more widespread than previously realized, although its relative importance is related to growth habit. Arborescent species of these fossil assemblages reproduce mainly asexually via fragmentation; encrusting species reproduce sexually via motile larvae. Free-living species use both methods; some reproduce sexually, whereas other species have enhanced the ability to break and reproduce predominantly asexually. Mode of reproduction was stable over a period of 3 m.y. in all species except the vinelike Columnotheca cribrosa. In this species both the proportion of asexual recruits and brooding zooids varied in accord with environmental parameters. In all cases populations dominated by asexual propagation had a significantly lower proportion of brooding zooids than populations dominated by sexual propagation.
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Amat, Isabelle, Jacques J. M. van Alphen, Alex Kacelnik, Emmanuel Desouhant, and Carlos Bernstein. "Adaptations to different habitats in sexual and asexual populations of parasitoid wasps: a meta-analysis." PeerJ 5 (September 12, 2017): e3699. http://dx.doi.org/10.7717/peerj.3699.
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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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Mee, J. A., and L. Rowe. "A comparison of parasite loads on asexual and sexual Phoxinus (Pisces: Cyprinidae)." Canadian Journal of Zoology 84, no. 6 (June 2006): 808–16. http://dx.doi.org/10.1139/z06-064.
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In light of the inherent disadvantages of sexual reproduction, the existence of sex is often seen as a paradox. There are a variety of hypothetical benefits of sexual reproduction that may balance its disadvantages. The Red Queen hypothesis proposes that sexually reproducing species are better able to evolve resistance to parasites than asexually reproducing species. A prediction of the Red Queen hypothesis is that a parasite should evolve to preferentially exploit an asexual species over a sexual species. To test this central prediction of the Red Queen hypothesis, intensity of infection by the parasite Gyrodactylus eos Mayes, 1977 (Monogenea) was compared between sympatric asexual and sexual fish species in the genus Phoxinus Rafinesque, 1820. In each lake where these species coexist, the asexual fish should suffer higher intensities of infection than the sexual fish. In the majority of lakes sampled, there were more parasites on asexual than sexual fish.
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Boyer, Loreleï, Roula Jabbour-Zahab, Pauline Joncour, Sylvain Glémin, Christoph R. Haag, and Thomas Lenormand. "Asexual male production by ZW recombination in Artemia parthenogenetica." Evolution 77, no. 1 (December 8, 2022): 1–12. http://dx.doi.org/10.1093/evolut/qpac008.
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Abstract In some asexual species, parthenogenetic females occasionally produce males, which may strongly affect the evolution and maintenance of asexuality if they cross with related sexuals and transmit genes causing asexuality to their offspring (“contagious parthenogenesis”). How these males arise in the first place has remained enigmatic, especially in species with sex chromosomes. Here, we test the hypothesis that rare, asexually produced males of the crustacean Artemia parthenogenetica are produced by recombination between the Z and W sex chromosomes during non-clonal parthenogenesis, resulting in ZZ males through loss of heterozygosity at the sex determination locus. We used RAD-sequencing to compare asexual mothers with their male and female offspring. Markers on several sex-chromosome scaffolds indeed lost heterozygosity in all male but no female offspring, suggesting that they correspond to the sex-determining region. Other sex-chromosome scaffolds lost heterozygosity in only a part of the male offspring, consistent with recombination occurring at a variable location. Alternative hypotheses for the production of these males (such as partial or total hemizygosity of the Z) could be excluded. Rare males are thus produced because recombination is not entirely suppressed during parthenogenesis in A. parthenogenetica. This finding may contribute to explaining the maintenance of recombination in these asexuals.
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Przybylo, E., and D. Cooper. "Asexual Resonances: Tracing a Queerly Asexual Archive." GLQ: A Journal of Lesbian and Gay Studies 20, no. 3 (January 1, 2014): 297–318. http://dx.doi.org/10.1215/10642684-2422683.
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Grosberg, Richard K., and Roger N. Hughes. "Asexual Obsessions." Evolution 46, no. 6 (December 1992): 1976. http://dx.doi.org/10.2307/2410050.
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Shoubridge, Eric A. "Asexual healing." Nature 461, no. 7262 (September 2009): 354–55. http://dx.doi.org/10.1038/461354a.
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MCCONNELL, J. "Asexual cycle." Lancet 344, no. 8914 (July 1994): 53. http://dx.doi.org/10.1016/s0140-6736(94)91073-1.
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Grosberg, Richard K. "ASEXUAL OBSESSIONS." Evolution 46, no. 6 (December 1992): 1976–79. http://dx.doi.org/10.1111/j.1558-5646.1992.tb01188.x.
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Pinto, Stacy Anne. "ASEXUally: On Being an Ally to the Asexual Community." Journal of LGBT Issues in Counseling 8, no. 4 (October 2, 2014): 331–43. http://dx.doi.org/10.1080/15538605.2014.960130.
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Carranza, Juan, and Vicente Polo. "Sexual reproduction with variable mating systems can resist asexuality in a rock–paper–scissors dynamics." Royal Society Open Science 2, no. 7 (July 2015): 140383. http://dx.doi.org/10.1098/rsos.140383.
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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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Wibowo, Anjar, Claude Becker, Julius Durr, Jonathan Price, Stijn Spaepen, Sally Hilton, Hadi Putra, et al. "Partial maintenance of organ-specific epigenetic marks during plant asexual reproduction leads to heritable phenotypic variation." Proceedings of the National Academy of Sciences 115, no. 39 (September 10, 2018): E9145—E9152. http://dx.doi.org/10.1073/pnas.1805371115.
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Plants differ from animals in their capability to easily regenerate fertile adult individuals from terminally differentiated cells. This unique developmental plasticity is commonly observed in nature, where many species can reproduce asexually through the ectopic initiation of organogenic or embryogenic developmental programs. While organ-specific epigenetic marks are not passed on during sexual reproduction, the fate of epigenetic marks during asexual reproduction and the implications for clonal progeny remain unclear. Here we report that organ-specific epigenetic imprints in Arabidopsis thaliana can be partially maintained during asexual propagation from somatic cells in which a zygotic program is artificially induced. The altered marks are inherited even over multiple rounds of sexual reproduction, becoming fixed in hybrids and resulting in heritable molecular and physiological phenotypes that depend on the identity of the founder tissue. Consequently, clonal plants display distinct interactions with beneficial and pathogenic microorganisms. Our results demonstrate how novel phenotypic variation in plants can be unlocked through altered inheritance of epigenetic marks upon asexual propagation.
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Harriott, VJ. "Reproductive biology of three congeneric sea cucumber species, Holothuria atra, H. impatiens and H. edulis, at Heron Reef, Great Barrier Reef." Marine and Freshwater Research 36, no. 1 (1985): 51. http://dx.doi.org/10.1071/mf9850051.
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Three Holothuria species at Heron Reef showed considerable variation in reproductive seasonality, magnitude of gonad index, egg size and numbers, and frequency of asexual reproduction by transverse binary fission. H. atra from the shallow lagoon spawned biannually (in summer and winter), females produced a large number of small ova, and asexual reproduction was frequent. H. impatiens from the reef flat spawned annually in late spring or summer, with females producing a small number of large ova; signs of asexual reproduction were never observed. H. edulis from the deep lagoon showed no annual reproductive pattern, produced an intermediate size and number of eggs, and reproduced asexually moderately frequently. Preliminary results indicated that reproductive maturation and magnitude of gonad index might vary between sites for H. atra. There was little temporal overlap in spawning by the three species at the sites sampled, and this may be a factor in the maintenance of their genetic isolation.
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Gerber, Nina, and Hanna Kokko. "Sexual conflict and the evolution of asexuality at low population densities." Proceedings of the Royal Society B: Biological Sciences 283, no. 1841 (October 26, 2016): 20161280. http://dx.doi.org/10.1098/rspb.2016.1280.
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Theories for the evolution of sex rarely include facultatively sexual reproduction. Sexual harassment by males is an underappreciated factor: it should at first sight increase the relative advantage of asexual reproduction by increasing the cost of sex. However, if the same females can perform either sexual or asexual life cycles, then females trying to reproduce asexually may not escape harassment. If resisting male harassment is costly, it might be beneficial for a female to accept a mating and undertake a sexual life cycle rather than ‘insist’ on an asexual one. We investigate the effects of sexual harassment on the maintenance of sex under different population densities. Our model shows that resisting matings pays off at low population densities, which leads to the complete extinction of males, and thus to the evolution of completely asexual populations. Facultative sex persists in a narrow range of slightly higher densities. At high densities, selection favours giving up resisting male mating attempts and thus sexual reproduction takes over. These interactions between the outcomes of sexual conflict and population density suggest an explanation for the rarity of facultative sex and also patterns of geographical parthenogenesis, where marginal environments with potentially low densities are associated with asexuality.
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Schwander, Tanja, Bernard J. Crespi, Regine Gries, and Gerhard Gries. "Neutral and selection-driven decay of sexual traits in asexual stick insects." Proceedings of the Royal Society B: Biological Sciences 280, no. 1764 (August 7, 2013): 20130823. http://dx.doi.org/10.1098/rspb.2013.0823.
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Environmental shifts and lifestyle changes may result in formerly adaptive traits becoming non-functional or maladaptive. The subsequent decay of such traits highlights the importance of natural selection for adaptations, yet its causes have rarely been investigated. To study the fate of formerly adaptive traits after lifestyle changes, we evaluated sexual traits in five independently derived asexual lineages, including traits that are specific to males and therefore not exposed to selection. At least four of the asexual lineages retained the capacity to produce males that display normal courtship behaviours and are able to fertilize eggs of females from related sexual species. The maintenance of male traits may stem from pleiotropy, or from these traits only regressing via drift, which may require millions of years to generate phenotypic effects. By contrast, we found parallel decay of sexual traits in females. Asexual females produced altered airborne and contact signals, had modified sperm storage organs, and lost the ability to fertilize their eggs, impeding reversals to sexual reproduction. Female sexual traits were decayed even in recently derived asexuals, suggesting that trait changes following the evolution of asexuality, when they occur, proceed rapidly and are driven by selective processes rather than drift.
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Hestmark, G. "To sex, or not to sex ... Structures and strategies of reproduction in the family Umbilicariaceae (Lecanorales, Ascomycetes)." Sommerfeltia 3, s3 (January 1, 1991): 1–52. http://dx.doi.org/10.2478/som-1991-0002.
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Abstract This is a study of the evolution and ecology of reproduction in the family of lichen-forming fungi U mbilicariaceae comprising the two genera Umbilicaria and Lasallia. Members of this family exhibit a variety of reproductive structures and strategies. The fungal partner of the symbiosis may reproduce by sexually generated ascospores, asexual thalloconidia, or both. Propagules reproducing the intact symbiosis include asexual isidia, soredia, thallyls, phyllidia and schizidia. The algal partner - unicellular Pseudotrebouxia (Chlorophyceae) - reproduces by asexual autospores when in symbiosis, and in addition zoospores and aplanospores in pure culture. In about half of the species in Umbilicariaceae the fungal partner can only reproduce sexually - it is exclusively teleomorphic. In these species, apparently, the option of asexual reproduction has not been presented by evolution. In the taxa where this option has been presented, the forces of ecology and evolution seem to favour this option. Although no tax.on with asexual reproduction appears to have dispensed with sexuality altogether, the allocation to sexual reproduction tends to decrease and the resources are translocated to asexual reproduction. Different taxa represent progressive stages in this de-evolution of sex. In some of these cases sex is correlated with geographical distribution patterns or ecological factors such as high humidity or high population density and sib-competition. The latter observation supports the ‘Tangled Bank’ hypothesis for the maintenance of sex, as well as ESS models for reproductive allocations in heterocarpic plants. In some cases exclusively teleomorphic tax.a co-exist with morphologically virtually identical but mainly asexual (anamorphic) taxa, suggesting that a difference in reproductive mode may have led to speciation. Associated with different propagule types are a number of other traits with consequences for the ecological performance of the species. These sets of correlated traits constitute strategies of reproduction, the core sets of specific life-history strategies. Three ‘pure’ reproductive strategies are tentatively distinguished in the Umbilicariaceae, depending on whether the propagule is sexually or asexually generated and whether it is symbiotic or not. The asexual propagules are close-dispersed while sexual propagules are more far-dispersed. A comparative study of the performance of representatives of the three strategy types in two glacier forelands shows that the sexually reproducing species are the fastest colonizers. The need to re-establish symbiosis at target site appears to be no great obstacle to sexual reproduction by ascospores.
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Yan, Zhi-Chao, Guang-Yuan Qi, Tian-Yi Yao, and Yuan-Xi Li. "Mitochondrial Genomes of Two Asexual Trichogramma (Hymenoptera: Trichogrammatidae) Strains and Comparison with Their Sexual Relatives." Insects 13, no. 6 (June 16, 2022): 549. http://dx.doi.org/10.3390/insects13060549.
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Despite its substantial costs, sexual reproduction dominates in animals. One popular explanation for the paradox of sex is that asexual reproduction is more likely to accumulate deleterious mutations than sexual reproduction. To test this hypothesis, we compared the mitogenomes of two asexual wasp strains, Trichogramma cacoeciae and T. pretiosum, to their sexual relatives. These two asexual strains represent two different transition mechanisms in Trichogramma from sexual to asexual reproduction. Asexual T. pretiosum is induced by Wolbachia, while T. cacoeciae presumably originated from interspecific hybridization. We sequenced and assembled complete mitochondrial genomes of asexual T. cacoeciae and T. pretiosum. Compared to four sexual relatives, we found no evidence of higher mutation accumulation in asexual Trichogramma mitogenomes than in their sexual relatives. We also did not detect any relaxed selection in asexual Trichogramma mitogenomes. In contrast, the intensified selection was detected in Nad1 and Nad4 of the asexual T. pretiosum mitogenome, suggesting more purifying selection. In summary, no higher mitochondrial mutation accumulation was detected in these two asexual Trichogramma strains. This study provides a basis for further investigating mitochondrial evolution and asexual reproduction in Trichogramma.
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Dana, Geraldina. "La comunidad virtual de asexuales del área metropolitana de Buenos Aires." Sexualidad, Salud y Sociedad (Rio de Janeiro), no. 34 (April 2020): 126–52. http://dx.doi.org/10.1590/1984-6487.sess.2020.34.08.a.
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Resumen El presente trabajo identifica y caracteriza a la comunidad asexual del Área Metro-politana de Buenos Aires. Para ello, en primer lugar, se lleva adelante una revisión teórica del concepto de asexualidad, destacando los aportes más relevantes para su incipiente estudio. En segundo lugar, como los asexuales se vinculan prioritariamente mediante plataformas virtuales, la metodología implementada es la de una etnografía virtual, combinándola con entrevistas en profundidad. Se busca, de este modo, dar cuenta de la especificidad de una comunidad forjada principalmente online. Por último, se desarrolla la politización de la co-munidad asexual, orientada al reconocimiento social del resto de la sociedad civil y de los colectivos de diversidad sexual.
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McNair, Mason, Amanda Wilkins, and Dennis Werner. "Wounding and chemical treatment effects on Drosera capensis bud formation on leaf cuttings." Carnivorous Plant Newsletter 41, no. 4 (December 1, 2012): 140–42. http://dx.doi.org/10.55360/cpn414.mm785.
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Drosera capensis L. (Droseraceae) is one of the most commonly grown carnivorous plants prized for its ease of culture and rapid growth. In cultivation, seed is preferred for propagating this species; however, in the case of cultivar propagation, asexual propagation must be used. D. capensis readily propagates from both leaf and root cuttings. Leaf cuttings can be used to asexually propagate D. capensis. Wounding and exogenous hormone applications are commonly used in herbaceous and woody plant asexual propagation to enhance adventitious root and shoot formation. The purpose of this study was to investigate the effect of wounding and exogenous hormone application (auxin and cytokinin) on adventitious shoot formation on leaf cuttings of D. capensis.
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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, no. 29 (July 21, 2015): 8851–58. http://dx.doi.org/10.1073/pnas.1501726112.
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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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Judson, Olivia P., and Benjamin B. Normark. "Ancient asexual scandals." Trends in Ecology & Evolution 11, no. 2 (February 1996): 41–46. http://dx.doi.org/10.1016/0169-5347(96)81040-8.
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Meirmans, P. G., H. C. M. Den Nijs, and P. H. Van Tienderen. "Male sterility in triploid dandelions: asexual females vs asexual hermaphrodites." Heredity 96, no. 1 (September 28, 2005): 45–52. http://dx.doi.org/10.1038/sj.hdy.6800750.
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Chen, Guanhan. "Research on the Development Path of Feminism from an Aromantic Asexual Perspective." Journal of Gender, Culture and Society 4, no. 2 (July 12, 2024): 34–38. http://dx.doi.org/10.32996/jgcs.2024.4.2.5.
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Aromantic asexual is a perspective that has rarely been used in the research of Feminism, and this paper aims to explore the possibility and significance of combining aromantic asexual and feminism to fight against “sexual hegemony” from the perspective of the social identity of aromantic asexual. This paper will carry out research through the following aspects: firstly, analyse the concept of aromantic asexual and clarify its connotation and characteristics; secondly, explore the historical basis of the combination of aromantic asexual and feminism and reveal the links and commonalities between the two; then analyse the reasons why aromantic asexual and feminism can move towards the union, and explore the motivation and possibilities of the combination of the two; finally, explore the reflection on the combination of aromantic asexual and feminism, and conclude that the combination of aromantic asexual and feminism has been a very important factor in the development of the feminist movement. Finally, it discusses the reflection on the combination of aromantic asexual and feminism and concludes that the combination of aromantic asexual and feminism is insufficient in resisting the path of “sexual hegemony.” The research in this paper shows that aromantic asexual and feminism have a certain historical basis and connection and that they share some common concepts and goals. At the same time, the combination of aromantic asexual and feminism is not accidental but may be based on the common resistance to and demand for the phenomenon of “sexual hegemony”. Therefore, the combination of aromantic asexual and feminism to fight against “sexual hegemony” has certain rationality and significance and can bring new inspiration and impetus to the cause of gender equality. However, it is also necessary to note that there may be shortcomings in practice, which need to be further studied and explored in depth. It is suggested that future research should strengthen the exploration of the combination of aromantic asexual and feminism, promote cooperation and development between the two, and provide more possibilities and support for the advancement of the cause of gender equality.
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Bennett-Smith, Morgan F., Micaela S. Justo, Michael L. Berumen, Raquel Peixoto, and Benjamin M. Titus. "Novel in situ observations of asexual reproduction in the carpet sea anemone, Stichodactyla mertensii (Stichodactylidae, Actiniaria)." ZooKeys 1103 (May 27, 2022): 57–63. http://dx.doi.org/10.3897/zookeys.1103.84415.
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Merten’s carpet sea anemone, Stichodactyla mertensii Brandt, 1835, is the largest known sea anemone species in the world, regularly exceeding one meter in oral disc diameter. A tropical species from the Indo-Pacific, S. mertensii drapes prominently over coral reef substrates and is a common host to numerous species of clownfishes and other symbionts throughout its range, which extends from the Red Sea through the Central Pacific Ocean. Long thought to reproduce via sexual reproduction only, recent genetic evidence suggests it may rarely reproduce asexually as well, although this process had never been confirmed through direct observation and the mechanism was yet to be described. Here, we directly observed and documented in situ asexual fragmentation via budding, in real time, by a Red Sea S. mertensii in a turbid inshore reef environment. While asexual reproduction is not unusual in sea anemones as a group, it is typically expected to be uncommon for large-bodied species. Herein, we describe S. mertensii fragmentation, provide high resolution images of the event from the Saudi Arabian coastline at multiple time points, and confirm asexual reproduction for this species.
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Riesch, Rüdiger, Ingo Schlupp, and Martin Plath. "Female sperm limitation in natural populations of a sexual/asexual mating complex ( Poecilia latipinna , Poecilia formosa )." Biology Letters 4, no. 3 (March 4, 2008): 266–69. http://dx.doi.org/10.1098/rsbl.2008.0019.
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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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Choleva, Lukáš, Apostolos Apostolou, Petr Ráb, and 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, no. 1505 (June 2, 2008): 2911–19. http://dx.doi.org/10.1098/rstb.2008.0059.
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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.
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Dańko, Aleksandra, Ralf Schaible, and Maciej J. Dańko. "Salinity Effects on Survival and Reproduction of Hydrozoan Eleutheria dichotoma." Estuaries and Coasts 43, no. 2 (December 23, 2019): 360–74. http://dx.doi.org/10.1007/s12237-019-00675-2.
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AbstractSalinity conditions experienced by organisms in coastal regions may shape their life histories. Here, salinity’s impact on reproduction and survival of the hydrozoan Eleutheria dichotoma was investigated using laboratory-cultured individuals originating from Banyuls-sur-Mer (southern France) collected several decades ago. During the experiment (October 2014–July 2015), hydroid colonies and medusae were exposed to three salinities (25, 35, 45). Asexually budded medusae were collected from colonies and reared for three generations obtained by asexual budding of medusae. Salinities experienced by hydroid colonies had only minor effects on initial size, time to maturity, medusa budding, sexual production of planulae by medusae, and survival. In contrast, salinities experienced by medusae influenced their life histories. Compared with medium salinity (35), low-salinity medusae (25) had an earlier onset and higher rates of asexual budding, a later onset and slower rates of sexual reproduction, and higher mortality, which could result from allocation tradeoffs. The increased production of planulae by medusae in low salinity indicated that they were transitioning to a benthic polyp life form more resistant to environmental stress. High salinity (45) delayed asexual maturity, prevented sexual maturity in medusae, and led to lower survival and asexual reproduction rates. Budding rates decreased across the generations; however, planula production rates decreased in medium salinity but increased in low salinity. This might be explained by the accumulation of damage with each generation, and/or by internal rhythms. The flexible responses of this tractable model organism, Eleutheria dichotoma, to salinity change may be useful in future studies on changing estuarine conditions.
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Orr, H. Allen. "The Rate of Adaptation in Asexuals." Genetics 155, no. 2 (June 1, 2000): 961–68. http://dx.doi.org/10.1093/genetics/155.2.961.
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Abstract I study the population genetics of adaptation in asexuals. I show that the rate of adaptive substitution in an asexual species or nonrecombining chromosome region is a bell-shaped function of the mutation rate: at some point, increasing the mutation rate decreases the rate of substitution. Curiously, the mutation rate that maximizes the rate of adaptation depends solely on the strength of selection against deleterious mutations. In particular, adaptation is fastest when the genomic rate of mutation, U, equals the harmonic mean of selection coefficients against deleterious mutations, where we assume that selection for favorable alleles is milder than that against deleterious ones. This simple result is independent of the shape of the distribution of effects among favorable and deleterious mutations, population size, and the action of clonal interference. In the course of this work, I derive an approximation to the probability of fixation of a favorable mutation in an asexual genome or nonrecombining chromosome region in which both favorable and deleterious mutations occur.
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Sun, Yanxia, Xu Zhang, Aidi Zhang, Jacob B. Landis, Huajie Zhang, Hang Sun, Qiu-Yun (Jenny) Xiang, and Hengchang Wang. "Population Genomic Analyses Suggest a Hybrid Origin, Cryptic Sexuality, and Decay of Genes Regulating Seed Development for the Putatively Strictly Asexual Kingdonia uniflora (Circaeasteraceae, Ranunculales)." International Journal of Molecular Sciences 24, no. 2 (January 11, 2023): 1451. http://dx.doi.org/10.3390/ijms24021451.
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Asexual lineages are perceived to be short-lived on evolutionary timescales. Hence, reports for exceptional cases of putative ‘ancient asexuals’ usually raise questions about the persistence of such species. So far, there have been few studies to solve the mystery in plants. The monotypic Kingdonia dating to the early Eocene, contains only K. uniflora that has no known definitive evidence for sexual reproduction nor records for having congeneric sexual species, raising the possibility that the species has persisted under strict asexuality for a long period of time. Here, we analyze whole genome polymorphism and divergence in K. uniflora. Our results show that K. uniflora is characterized by high allelic heterozygosity and elevated πN/πS ratio, in line with theoretical expectations under asexual evolution. Allele frequency spectrum analysis reveals the origin of asexuality in K. uniflora occurred prior to lineage differentiation of the species. Although divergence within K. uniflora individuals exceeds that between populations, the topologies of the two haplotype trees, however, fail to match each other, indicating long-term asexuality is unlikely to account for the high allele divergence and K. uniflora may have a recent hybrid origin. Phi-test shows a statistical probability of recombination for the conflicting phylogenetic signals revealed by the split network, suggesting K. uniflora engages in undetected sexual reproduction. Detection of elevated genetic differentiation and premature stop codons (in some populations) in genes regulating seed development indicates mutational degradation of sexuality-specific genes in K. uniflora. This study unfolds the origin and persistence mechanism of a plant lineage that has been known to reproduce asexually and presents the genomic consequences of lack of sexuality.
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Fine, Julia Coombs. "From crushes to squishes." Journal of Language and Sexuality 12, no. 2 (July 13, 2023): 145–72. http://dx.doi.org/10.1075/jls.22004.fin.
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Abstract Previous research on language, sexuality, and affect has focused primarily on the presence rather than the absence of desire. This analysis investigates the linguistic manifestations of non-desire on two subreddits: r/AskReddit and r/Asexual. Contrasting asexual redditors’ responses to threads such as When and how did you realize you were asexual? with straight, allosexual redditors’ responses to a thread titled Straight redditors, when did you realize you were straight?, I find that allosexual and asexual redditors’ responses differ in agency and emotionality. While straight allosexual redditors attribute their lack of homosexual desire to factors other than themselves, asexual redditors attribute their lack of allosexual desire to their own identity. Additionally, asexual redditors frame their realizations of their asexuality as processual and emotional, using feel and felt more often than straight allosexual redditors’ responses. These results expose the importance of emotionality – including lack of desire – as a resource for asexual identity construction.
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Mollet, Amanda L., and Brian R. Lackman. "Asexual Borderlands: Asexual Collegians’ Reflections on Inclusion Under the LGBTQ Umbrella." Journal of College Student Development 59, no. 5 (2018): 623–28. http://dx.doi.org/10.1353/csd.2018.0058.
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Tabata, Jun, Ryoko T. Ichiki, Chie Moromizato, and Kenji Mori. "Sex pheromone of a coccoid insect with sexual and asexual lineages: fate of an ancestrally essential sexual signal in parthenogenetic females." Journal of The Royal Society Interface 14, no. 128 (March 2017): 20170027. http://dx.doi.org/10.1098/rsif.2017.0027.
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Sex pheromones play a central role in intersexual communication for reproduction in many organisms. Particularly in insects, reproductive isolation that leads to speciation is often achieved by shifts of pheromone chemistries. However, the divergence and evolution of pheromones remain largely unknown. This study reveals a unique evolutionary consequence for terpenoid pheromones in coccoid insects. Coccoids, such as mealybugs, show clear sexual dimorphism: males are dwarf and short-lived, whereas females are wingless and almost immobile. Female pheromones are therefore indispensable for males to navigate for sexual reproduction, but some females can reproduce asexually. Interestingly, a derived asexual lineage that reproduces by parthenogenesis coexists with its ancestral lineage that reproduces sexually in a population of the pineapple mealybug, Dysmicoccus brevipes . Here, we isolated, characterized and synthesized a novel monoterpene, (−)-( anti -1,2-dimethyl-3-methylenecyclopentyl)acetaldehyde, as a pheromone of the sexual females of D . brevipes . This monoterpene aldehyde, with an irregular linkage of isoprene units, is notable, because all mealybug pheromones previously reported are carboxylic esters of terpenols. This compound was, however, never produced by the asexual females. As a consequence of acquiring parthenogenetic reproduction, the asexual females appear to have abandoned the production of the sex pheromone, which had been essential to attracting males in their ancestors.
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Stelzer, Claus-Peter, and Jussi Lehtonen. "Diapause and maintenance of facultative sexual reproductive strategies." Philosophical Transactions of the Royal Society B: Biological Sciences 371, no. 1706 (October 19, 2016): 20150536. http://dx.doi.org/10.1098/rstb.2015.0536.
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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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BSc, Erin Hampson. "Negotiating (in)visibility: A phenomenological analysis of asexual students’ experiences of university." Psychology of Sexualities Review 11, no. 1 (2020): 26–41. http://dx.doi.org/10.53841/bpssex.2020.11.1.26.
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Asexuality research is an emerging topic and understanding gained through the perspectives of asexuals offer insights into how asexuality is experienced within social contexts. This exploratory study sought to understand the everyday experiences of self-identified asexuals within university contexts, the challenges they face and the ways in which these are understood and navigated. Four participants, attending UK universities, were recruited through lesbian, gay, bisexual, trans, queer, intersex and asexual (LGBTQIA+) Facebook groups. Data was collected through photo-elicitation interviews and analysed using interpretive phenomenological analysis, through which three superordinate themes were developed: navigating normative social space, navigating (in)visibility and coming out and creating safer spaces. These, along with their subordinate themes, are outlined and then discussed in relation to existing literature and recommendations for future research are made.
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Schön, Isa, Fernando Rodriguez, Matthew Dunn, Koen Martens, Michael Shribak, and Irina R. Arkhipova. "A Survey of Transposon Landscapes in the Putative Ancient Asexual Ostracod Darwinula stevensoni." Genes 12, no. 3 (March 11, 2021): 401. http://dx.doi.org/10.3390/genes12030401.
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How asexual reproduction shapes transposable element (TE) content and diversity in eukaryotic genomes remains debated. We performed an initial survey of TE load and diversity in the putative ancient asexual ostracod Darwinula stevensoni. We examined long contiguous stretches of DNA in clones from a genomic fosmid library, totaling about 2.5 Mb, and supplemented these data with results on TE abundance and diversity from an Illumina draft genome. In contrast to other TE studies in putatively ancient asexuals, which revealed relatively low TE content, we found that at least 19% of the fosmid dataset and 26% of the genome assembly corresponded to known transposons. We observed a high diversity of transposon families, including LINE, gypsy, PLE, mariner/Tc, hAT, CMC, Sola2, Ginger, Merlin, Harbinger, MITEs and helitrons, with the prevalence of DNA transposons. The predominantly low levels of sequence diversity indicate that many TEs are or have recently been active. In the fosmid data, no correlation was found between telomeric repeats and non-LTR retrotransposons, which are present near telomeres in other taxa. Most TEs in the fosmid data were located outside of introns and almost none were found in exons. We also report an N-terminal Myb/SANT-like DNA-binding domain in site-specific R4/Dong non-LTR retrotransposons. Although initial results on transposable loads need to be verified with high quality draft genomes, this study provides important first insights into TE dynamics in putative ancient asexual ostracods.
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Caldeira, Cecilio F., Arthur V. S. Lopes, Keyvilla C. Aguiar, Aline L. Ferreira, João V. S. Araujo, Vinnícius M. S. Gomes, Daniel B. Zandonadi, et al. "Distinct Reproductive Strategy of Two Endemic Amazonian Quillworts." Diversity 13, no. 8 (July 29, 2021): 348. http://dx.doi.org/10.3390/d13080348.
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We examined the reproductive strategy of two Amazonian quillworts (Isoëtes cangae and Isoëtes serracarajensis), endemic and threatened species of canga ecosystems. Sexual propagation was examined by in vitro fertilization assays, while asexual propagation was examined by tiller emission. Isoëtes cangae is an outcrossing species that reproduces exclusively by spore germination and is able to propagate by self- and cross-fertilization. Isoëtes serracarajensis reproduces asexually by emitting tillers from the plant corm, despite producing male and female sporangia. These distinct reproductive strategies in the different species may be linked to their contrasting habitats. Isoëtes cangae inhabit a permanent oligotrophic lake with mild environmental changes, while I. serracarajensis are found in temporary ponds facing severe seasonal drought, where asexual propagation may represent an adaptive advantage to the short growth period during access to water. We also observed different relationships between plant growth and reproductive traits between the species, despite their common production of sporophytes with high survival rates. Together, these results are of paramount importance for establishing conservation plans for both species considering the advantages of sexual propagation to maintain the genetic diversity of I. cangae and the diligent management required to do the same with asexually propagated I. serracarajensis.
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TRIPP, Erin A. "Is asexual reproduction an evolutionary dead end in lichens?" Lichenologist 48, no. 5 (September 2016): 559–80. http://dx.doi.org/10.1017/s0024282916000335.
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AbstractClassical hypotheses in lichenology predict pairs of species in which sexual lineages are ancestral and long-lived evolutionarily and that these give rise to derived, evolutionarily transient asexual lineages. Extensive phylogenetic information generated over the last 20 years regarding relationships within and among various groups of lichens makes possible an investigation of polarity and lability in reproductive mode across diverse clades. To test the long-held hypothesis of asexual reproduction as an evolutionary dead end in lichens, existing phylogenetic data from 23 studies were utilized to reconstruct gains and losses of sexual and asexual reproduction in a model-based statistical framework. Summed across all studies, between 26–44 origins of asexual reproduction from sexual ancestors (forward transitions) and 14–25 origins of sexual reproduction from asexual ancestors (reverse transitions) were identified. However, the higher number of gains of asexual reproduction was concentrated in a relatively low number of clades (e.g. Dirina). The greater number of forward compared to reverse transitions is consistent with dogma in both lichenology and evolutionary biology, but nonetheless this study documents numerous reverse transitions, suggesting that asexual lineages represent a source for evolutionary innovation.
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Hall, Scott, David Knox, and I. Joyce Chang. "Out of the Shadow and Into the Light: New Data Comparing Asexual and Sexual Undergraduates." Journal of Positive Sexuality 7, no. 2 (December 1, 2021): 63–77. http://dx.doi.org/10.51681/1.722.
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Drawing from a large dataset of over 13,000 college students, this research compared 75 self-identified asexual individuals with heterosexual, bisexual, and gay/lesbian undergraduates. The results revealed that asexual individuals were less likely to have engaged in sexual behaviors (oral sex, anal sex, friends with benefits, sexual intercourse, hooking up) than heterosexual, bisexual, and gay or lesbian individuals. Asexual and heterosexual individuals were similar in endorsing absolutist sexual values, having a lower willingness to cohabit, and reporting less likelihood of having masturbated. Asexual individuals were similar to other sexual minorities in being less religious and having more positive attitudes toward LGB issues. A multinomial logistic regression analysis using all the variables with significant differences at the bivariate level revealed similar findings, though asexual individuals differed most dramatically in their lower levels of sexual experience when compared to gay/lesbian individuals. Future researchers are encouraged to consider reframing asexuality as more sex positive so as to recognize diversity and empower asexual individuals.
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Adachi-Hagimori, Tetsuya, and Kazuki Miura. "Limited Mating Ability of a Wasp Strain with Rickettsia-Induced Thelytoky." Annals of the Entomological Society of America 113, no. 5 (April 30, 2020): 355–58. http://dx.doi.org/10.1093/aesa/saaa007.
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Abstract Sexual reproduction is the dominant mode of reproduction in plants and animals; however, some species from various taxonomic groups reproduce asexually. Because some of these asexual species lack DNA recombination and so have low genetic variability, these asexual species are more likely to go extinct than sexual species. Neochrysocharis formosa (Westwood) (Hymenoptera: Eulophidae) is a solitary endoparasitoid in which both arrhenotokous and thelytokous strains occur in sympatry. The thelytokous strain is infected by a parthenogenesis-inducing Rickettsia bacterium. We investigated whether fertilized progeny can be produced between females and antibiotic-induced males of the thelytokous strain. The males produced by antibiotic treatment showed the same courtship behaviors as the arrhenotokous males, but at a lower rate, and did not produce fertilized progeny. The results confirm that the thelytokous strain has been maintained by a functional apomixis mechanism rather than by occasional sex, preserving a degree of heterozygosity.
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Dolmatov, Igor Yu. "Asexual Reproduction in Holothurians." Scientific World Journal 2014 (2014): 1–13. http://dx.doi.org/10.1155/2014/527234.
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Aspects of asexual reproduction in holothurians are discussed. Holothurians are significant as fishery and aquaculture items and have high commercial value. The last review on holothurian asexual reproduction was published 18 years ago and included only 8 species. An analysis of the available literature shows that asexual reproduction has now been confirmed in 16 holothurian species. Five additional species are also most likely capable of fission. The recent discovery of new fissiparous holothurian species indicates that this reproduction mode is more widespread in Holothuroidea than previously believed. New data about the history of the discovery of asexual reproduction in holothurians, features of fission, and regeneration of anterior and posterior fragments are described here. Asexual reproduction is obviously controlled by the integrated systems of the organism, primarily the nervous system. Special molecular mechanisms appear to determine the location where fission occurs along the anterior-posterior axis of the body. Alteration of the connective tissue strength of the body wall may play an important role during fission of holothurians. The basic mechanism of fission is the interaction of matrix metalloproteinases, their inhibitors, and enzymes forming cross-link complexes between fibrils of collagen. The population dynamics of fissiparous holothurians are discussed.
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Howard, Russell J. "Asexual deviants take over." Nature 357, no. 6380 (June 1992): 647–48. http://dx.doi.org/10.1038/357647a0.
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Vielle Calzada, J. P., C. F. Crane, and D. M. Stelly. "Apomixis--The Asexual Revolution." Science 274, no. 5291 (November 22, 1996): 1322–23. http://dx.doi.org/10.1126/science.274.5291.1322.
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Martinez, D. E., and J. S. Levinton. "Asexual metazoans undergo senescence." Proceedings of the National Academy of Sciences 89, no. 20 (October 15, 1992): 9920–23. http://dx.doi.org/10.1073/pnas.89.20.9920.
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Nelson, Amanda E., and Maurine Neiman. "Persistent Copulation in Asexual Female Potamopyrgus antipodarum: Evidence for Male Control with Size-Based Preferences." International Journal of Evolutionary Biology 2011 (April 10, 2011): 1–7. http://dx.doi.org/10.4061/2011/439046.
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Transitions from sexual to asexual reproduction provide a useful context for investigating the evolutionary loss of nonfunctional traits. It is often assumed that useless behaviors or structures will degrade, but this process is poorly understood. Potamopyrgus antipodarum is an ancestrally sexual New Zealand freshwater snail characterized by numerous independent transitions to asexual all-female lineages. The availability of multiple independently-derived asexual lineages of various time since derivation from sexual ancestors means that the P. antipodarum system is well-suited for the study of trait loss related to mating behavior and copulation. Here, we asked whether mating behavior in asexual female P. antipodarum degrades with increasing asexual lineage age. While copulation frequency did not differ in females from old versus young asexual lineages, post hoc analyses indicated that it was instead positively associated with mean lineage female size. We observed that female P. antipodarum take a passive physical role in copulatory interactions, indicating that female behavior may not be a useful variable for detection of sex-related vestigialization in this system. Instead, males seem to be in proximate control of copulation frequencies, meaning that male mating behavior may be a primary determinant of the expression of mating behavior in asexual female P. antipodarum.
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Innes, David J., and Michael Ginn. "A population of sexual Daphnia pulex resists invasion by asexual clones." Proceedings of the Royal Society B: Biological Sciences 281, no. 1788 (August 7, 2014): 20140564. http://dx.doi.org/10.1098/rspb.2014.0564.
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Asexual reproduction avoids the costs associated with sex, predicting that invading asexual clones can quickly replace sexual populations. Daphnia pulex populations in the Great Lakes area are predominately asexual, but the elimination of sexual populations by invading clones is poorly understood. Asexual clones were detected at low frequency in one rare sexual population in 1995, with some increase in frequency during 2003 and 2004. However, these clones remained at low frequency during further yearly sampling (2005–2013) with no evidence that the resident sexual population was in danger of elimination. There was evidence for hybridization between rare males produced by asexual clones and sexual females with the potential to produce new asexual genotypes and spread the genetic factors for asexuality. In a short-term laboratory competition experiment, the two most common asexual clones did not increase in frequency relative to a genetically diverse sexual population due in part to a greater investment in diapausing eggs that trades-off current population growth for increased contribution to the egg bank. Our results suggest that a successful invasion can be prolonged, requiring a combination of clonal genotypes with high fitness, persistence of clones in the egg bank and negative factors affecting the sexual population such as inbreeding depression resulting from population bottlenecks.