Throwing dice, but not always: bet-hedging strategy of parthenogenesis

Throwing dice, but not always: bet-hedging strategy of parthenogenesis | bioRxiv /* */ /* */ <!-- <!-- /*! * yepnope1.5.4 * (c) WTFPL, GPLv2 */ (function(a,b,c){function d(a){return"[object Function]"==o.call(a)}function e(a){return"string"==typeof a}function f(){}function g(a){return!a||"loaded"==a||"complete"==a||"uninitialized"==a}function h(){var a=p.shift();q=1,a?a.t?m(function(){("c"==a.t?B.injectCss:B.injectJs)(a.s,0,a.a,a.x,a.e,1)},0):(a(),h()):q=0}function i(a,c,d,e,f,i,j){function k(b){if(!o&&g(l.readyState)&&(u.r=o=1,!q&&h(),l.onload=l.onreadystatechange=null,b)){"img"!=a&&m(function(){t.removeChild(l)},50);for(var d in y[c])y[c].hasOwnProperty(d)&&y[c][d].onload()}}var j=j||B.errorTimeout,l=b.createElement(a),o=0,r=0,u={t:d,s:c,e:f,a:i,x:j};1===y[c]&&(r=1,y[c]=[]),"object"==a?l.data=c:(l.src=c,l.type=a),l.width=l.height="0",l.onerror=l.onload=l.onreadystatechange=function(){k.call(this,r)},p.splice(e,0,u),"img"!=a&&(r||2===y[c]?(t.insertBefore(l,s?null:n),m(k,j)):y[c].push(l))}function j(a,b,c,d,f){return q=0,b=b||"j",e(a)?i("c"==b?v:u,a,b,this.i++,c,d,f):(p.splice(this.i++,0,a),1==p.length&&h()),this}function k(){var a=B;return a.loader={load:j,i:0},a}var l=b.documentElement,m=a.setTimeout,n=b.getElementsByTagName("script")[0],o={}.toString,p=[],q=0,r="MozAppearance"in l.style,s=r&&!!b.createRange().compareNode,t=s?l:n.parentNode,l=a.opera&&"[object Opera]"==o.call(a.opera),l=!!b.attachEvent&&!l,u=r?"object":l?"script":"img",v=l?"script":u,w=Array.isArray||function(a){return"[object Array]"==o.call(a)},x=[],y={},z={timeout:function(a,b){return b.length&&(a.timeout=b[0]),a}},A,B;B=function(a){function b(a){var a=a.split("!"),b=x.length,c=a.pop(),d=a.length,c={url:c,origUrl:c,prefixes:a},e,f,g;for(f=0;f<d;f++)g=a[f].split("="),(e=z[g.shift()])&&(c=e(c,g));for(f=0;f<b;f++)c=x[f](c);return c}function g(a,e,f,g,h){var i=b(a),j=i.autoCallback;i.url.split(".").pop().split("?").shift(),i.bypass||(e&&(e=d(e)?e:e[a]||e[g]||e[a.split("/").pop().split("?")[0]]),i.instead?i.instead(a,e,f,g,h):(y[i.url]?i.noexec=!0:y[i.url]=1,f.load(i.url,i.forceCSS||!i.forceJS&&"css"==i.url.split(".").pop().split("?").shift()?"c":c,i.noexec,i.attrs,i.timeout),(d(e)||d(j))&&f.load(function(){k(),e&&e(i.origUrl,h,g),j&&j(i.origUrl,h,g),y[i.url]=2})))}function h(a,b){function c(a,c){if(a){if(e(a))c||(j=function(){var a=[].slice.call(arguments);k.apply(this,a),l()}),g(a,j,b,0,h);else if(Object(a)===a)for(n in m=function(){var b=0,c;for(c in a)a.hasOwnProperty(c)&&b++;return b}(),a)a.hasOwnProperty(n)&&(!c&&!--m&&(d(j)?j=function(){var a=[].slice.call(arguments);k.apply(this,a),l()}:j[n]=function(a){return function(){var b=[].slice.call(arguments);a&&a.apply(this,b),l()}}(k[n])),g(a[n],j,b,n,h))}else!c&&l()}var h=!!a.test,i=a.load||a.both,j=a.callback||f,k=j,l=a.complete||f,m,n;c(h?a.yep:a.nope,!!i),i&&c(i)}var i,j,l=this.yepnope.loader;if(e(a))g(a,0,l,0);else if(w(a))for(i=0;i (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0];var j=d.createElement(s);var dl=l!='dataLayer'?'&l='+l:'';j.src='//www.googletagmanager.com/gtm.js?id='+i+dl;j.type='text/javascript';j.async=true;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-M677548'); Skip to main content Home About Submit ALERTS / RSS Search for this keyword Advanced Search New Results Throwing dice, but not always: bet-hedging strategy of parthenogenesis Yanchao Chai doi: https://doi.org/10.1101/2025.11.05.686691 Yanchao Chai a Marine Science and Engineering College, Nanjing Normal University , 1 Wenyuan Road, Nanjing 210023, China b Hainan University , 58 People Road, Haikou 570228, China Find this author on Google Scholar Find this author on PubMed Search for this author on this site For correspondence: ycchai{at}yeah.net Abstract Full Text Info/History Metrics Preview PDF Abstract Parthenogenesis, clonal propagation by only female, is a common asexual reproduction model. Without sexual gene recombination, it is hypothesized that the deficiency of genotypic variation and accumulation of deleterious mutations reduce the fitness of parthenogenetic lineages confronted with environmental fluctuations, which is also regarded as evolutionary dead end. There should be specific life-history strategies to explain why parthenogenesis has been existing successfully. We constructed a family pedigree for rotifer spanning six generations, comprising 1200 individuals with identical genetic background in uniform condition, tracing back to the inception of parthenogenesis from single dormant egg. The individual fitness represented by lifespan and fecundity exhibits rich variation, and seems to be determined before birth by maternal stochastic investment among clutches regardless of maternal aging. Alike to “Do not put all your eggs in one basket”, this bet-hedging strategy spreads risk of environmental unpredictability. Despite the absence of sexual recombination, the phenotypic fitness failed to achieve fixation and heritability, instead demonstrating transgenerational compensation and trade-offs phenomenon. More siblings mean less children, and vice versa. This can be regarded as intrinsic and innate non-density-dependent self-regulation strategy of population, as limited by the conservation of disposable energy for allocation among offspring. Those strategies are conducive to explain the adaptability of parthenogenesis in evolution. Introduction The fitness for population maintenance is the ultimate aim in evolution, illustrated by successive generation-passage through reproduction 1 , 2 . The co-existence of different reproductive models (e.g., asexual vs. sexual) brings controversy around which one is “jack-of-all-trade” confronting with environmental fluctuations 3 - 5 . The variable genotype then phenotype become countermeasure for this selection pressure. Due to the deficient gene recombination and accumulation of deleterious mutations, the asexual reproduction is always regarded as an evolutionary “dead end” 3 . Paradoxically, asexual lineages are as common as sexual in many ancient organism lineages such as rotifers 6 , which requires more explanations on the adaptive reproductive strategies. Phenotypic plasticity and bet hedging have been regarded as main strategy for coping with predictable and unpredictable environmental changes, respectively 7 . For asexual lineages, non-genetic polymorphism, a typical plasticity, needs to be triggered by special environmental signal 7 , 8 . Compared to predictable varieties (i.e., periodic or recurring changes), the unpredictable one makes more survival risks and selection pressures. Bet hedging occurs when a single genotype produces fitness variance in offspring in advance of future unpredictable conditions 9 , 10 . Alike to “Do not put all your eggs in one basket”, bet hedging is bound to the randomness on maternal resource allocation to max long-term fitness of population 11 . The resource allocation can be directly reflected in fecundity and longevity of offspring, namely individual fitness 12 . It has been shown that the joint strategy mixing plasticity and bet hedging can be more successful, and randomly decides which one to adopt by “coin-flipping” way 11 . But, to some extents, this strategy depends on predictable cues. For asexual lineages, the direct empirical evidence on pure bet-hedging potential in advance of environmental unpredictability is still scarce. On the contrary, the effect of maternal age, a regularity in reproduction, seems to limit the randomness of fitness allocation 13 . In rotifers, asexual and sexual lineages coexist facultatively or obligately, which provides ideal materials for their evolution 7 . In parthenogenetic population, sexual mixis occur periodically to produce resting egg diapause against harsh conditions, but reduce population size, which spreads long-term risks at the expense of current benefits 8 . The variance on diapause-related traits has been regarded as the bet hedging of parthenogenesis in confront environmental fluctuation 8 . Nevertheless, this strategy still depends on sexual reproductive, which is impractical in some obligate asexual lineages. Other types of bet hedging strategies based on randomness may exist to support fitness of parthenogenesis. Therefore, we established parthenogenetically a clonal family (6 generations and 1200 individuals) of Brachionus calyciflorus cultivated individually in uniform condition (see Methods for details), and tracked individual longevity and fecundity. The potential reproductive strategies could be explored based on random variability within single genotype. Materials and methods The cloned strain of rotifer Brachionus calyciflorus originated from a resting egg, onset of facultative parthenogenesis. After hatched in 24-well plate with culture medium (96 mg NaHCO 3 , 60 mg CaSO 4 , 60 mg MgSO 4 and 4 mg KCl in 1 L distilled water) including 5×10 6 cell/ml Chlorella pyrenoidesa , the stem individual (F0) was observed every 12 hours, and every newborn larva (F1) was taken out and transferred to single well with 1 mL new culture medium to avoid peer pressure. Repeated this process until population size reached 1200 individuals span 6 generations ( Fig. 1 ). The culture condition was kept constantly in illumination incubator with 16L:8D light schedule with light intensity of 4000 Lux at 25°C. The individual offspring number, birth and death times were recorded. Download figure Open in new tab Fig. 1. Establishment of parthenogenetic family pedigree Results and discussion Although there was identical gene background, individuals’ lifespan and fecundity exhibited high variability with 39% and 65% coefficient of variation under same and stable environment without competitive pressure ( Fig. 2 ). This reflects evident and huge potential for phenotypic plasticity in the parthenogenetic cloned population. Download figure Open in new tab Fig. 2. Histogram of individual lifespan and fecundity distribution Download figure Open in new tab Fig. 2. Correlation between parental fecundity and variation of filial fecundity (difference between average fecundity of filial individuals and their parental fecundity) There was a positive correlation between lifespan and fecundity ( Fig. 3 ). Occasionally, under the premise of conservation of individual total disposable capacity, lifespan and fecundity show negative correlation due to trade-offs of energy allocation among survival, growth and reproduction. That is how organisms contain survival by suppress reproduction confronting with stressed conditions. In consideration of same and comfortable culture conditions in this study, it is logical to deduce that individuals were endowed with different capacity before birth, namely, fitness generally represented by lifespan and fecundity. It is like innate determinism theory based on maternal energy allocation. Download figure Open in new tab Fig. 3. Correlation between lifespan and fecundity The maternal energy allocation among siblings showed random pattern, as those individuals from different clutches of same mother had similar offspring number distribution regardless of maternal aging effect. And the fecundity variation within clutches could explain variation of entire population ( Fig. 4 ). The maternal random investment to children, like bet-hedging strategy, attributes to the phenotypic plasticity. Download figure Open in new tab Fig. 4. Fecundity variation across clutches The trait of fecundity characterize by maternal investment could not be inherited by the next generation, as there was no evident correlation between maternal and filial fecundity ( Fig. 5 ). As an advantage of asexual reproduction, it is assumed that the excellent traits can be fixed and inheritable owing to the absence of gene recombination. Nevertheless, this hypothesis seems to be invalid for parthenogenesis, and plasticity still dominates intergenerational transmission of phenotype overriding genotype. Download figure Open in new tab Fig. 5. Correlation between parental and filial fecundity This phenotypic plasticity was not entirely random, but which was control by the transgenerational trade-offs ( Fig. 5 ). To put it another way, if mother produces excessive children, those children’s fecundity will decrease, namely, there is a compensation point. In this study, the point value ranges from 4 to 5, which corresponds with the population fecundity histogram ( Fig. 1 ). Thus, this trade-offs response can be interpreted as a mechanism for population self-regulation coping with unpredictable environmental shocks. The suppressed fecundity under harsh conditions can be compensated in offspring for population restoration once upturn. Meanwhile, excessive reproduction will inhibit fecundity in next generation as a self-thinning to weaken intraclonal competition. Reference 1. ↵ Mark R. Christiea ; Gordon G. McNicklec ; Rod A. Frenche ; Blouin , M.S. , Life history variation is maintained by fitness trade-offs and negative frequency-dependent selection . Proceedings of the National Academy of Sciences of the United States of America 2018 , 115 , ( 17 ), 4441 – 4446 . OpenUrl Abstract / FREE Full Text 2. ↵ McGraw , J. B. ; Caswell , H. , Estimation of individual fitness from life-history data . The American Naturalist 2014 , 147 , ( 1 ), 47 – 64 . OpenUrl 3. ↵ Lodé , T. , Adaptive Significance and Long-Term Survival of Asexual Lineages . Evolutionary Biology 2012 , 40 , ( 3 ), 450 – 460 . OpenUrl 4. Park , A. W. ; Vandekerkhove , J. ; Michalakis , Y. , Sex in an uncertain world: environmental stochasticity helps restore competitive balance between sexually and asexually reproducing populations . Journal of Evolutionary Biology 2014 , 27 , ( 8 ), 1650 – 1661 . OpenUrl PubMed 5. ↵ Maraun , M. ; Bischof , P. S. P. ; Klemp , F. L. ; Pollack , J. ; Raab , L. ; Schmerbach , J. ; Schaefer , I. ; Scheu , S. ; Caruso , T. , “Jack-of-all-trades” is parthenogenetic . Ecology and Evolution 2022 , 12 , ( 6 ). 6. ↵ Becks , L. ; Agrawal , A. F. , The effect of sex on the mean and variance of fitness in facultatively sexual rotifers . Journal of evolutionary biology 2010 , 24 , 656 – 664 . OpenUrl PubMed 7. ↵ Franch-Gras , L. ; Tarazona , E. ; M, E.; Garcá-Roger Carmona , M.a.J. ; Gómez , A. ; Serra , M. , Rotifer adaptation to the unpredictability of the growing season . Hydrobiologia 2019 , 844 , 257 – 273 . OpenUrl 8. ↵ Gilbert , J. J. , Non-genetic polymorphisms in rotifers environmental and endogenous controls, development, and features for predictable or unpredictable environments . Biological Reviews 2017 , 92 , 964 – 992 . OpenUrl CrossRef 9. ↵ Einum , S. ; Fleming , I. A. , Environmental unpredictability and offspring size Conservative versus diversified bet-hedging . Evolutionary Ecology Research 2004 , 6 , 443 – 455 . OpenUrl Web of Science 10. ↵ Crean , A. J. ; Marshall , D. J. , Coping with environmental uncertainty dynamic bet hedging as a maternal effect . Philosophical transaction of The Royal Society B 2009 , 364 , 1087 – 1096 . OpenUrl CrossRef PubMed 11. ↵ Cooper , W. S. ; Kaplan , R. H. , Adaptive “coin-flipping” : a decision-theoretic examination of natural selection for random individual variation . 1982 , 94 , 135 – 151 . OpenUrl 12. ↵ Moore , M. P. ; Landberg , T. ; Whiteman , H. H. , Maternal investment mediates offspring life history variation with context-dependent fitness consequences . Ecology 2015 , 96 , ( 9 ), 2499 – 2509 . OpenUrl CrossRef PubMed 13. ↵ Gilbert , J. J. ; Schroder , T. , Intraclonal variation in propensity for mixis in several rotifers variation among females and with maternal age . Hydrobiologia 2007 , 593 , 121 – 128 . OpenUrl CrossRef Web of Science View the discussion thread. Back to top Previous Next Posted November 06, 2025. Download PDF Email Thank you for your interest in spreading the word about bioRxiv. NOTE: Your email address is requested solely to identify you as the sender of this article. Your Email * Your Name * Send To * Enter multiple addresses on separate lines or separate them with commas. You are going to email the following Throwing dice, but not always: bet-hedging strategy of parthenogenesis Message Subject (Your Name) has forwarded a page to you from bioRxiv Message Body (Your Name) thought you would like to see this page from the bioRxiv website. Your Personal Message CAPTCHA This question is for testing whether or not you are a human visitor and to prevent automated spam submissions. Share Throwing dice, but not always: bet-hedging strategy of parthenogenesis Yanchao Chai bioRxiv 2025.11.05.686691; doi: https://doi.org/10.1101/2025.11.05.686691 Share This Article: Copy Citation Tools Throwing dice, but not always: bet-hedging strategy of parthenogenesis Yanchao Chai bioRxiv 2025.11.05.686691; doi: https://doi.org/10.1101/2025.11.05.686691 Citation Manager Formats BibTeX Bookends EasyBib EndNote (tagged) EndNote 8 (xml) Medlars Mendeley Papers RefWorks Tagged Ref Manager RIS Zotero Tweet Widget Facebook Like Google Plus One Subject Area Zoology Subject Areas All Articles Animal Behavior and Cognition (7629) Biochemistry (17660) Bioengineering (13881) Bioinformatics (41911) Biophysics (21436) Cancer Biology (18578) Cell Biology (25482) Clinical Trials (138) Developmental Biology (13371) Ecology (19887) Epidemiology (2067) Evolutionary Biology (24302) Genetics (15599) Genomics (22483) Immunology (17728) Microbiology (40364) Molecular Biology (17163) Neuroscience (88537) Paleontology (666) Pathology (2830) Pharmacology and Toxicology (4821) Physiology (7637) Plant Biology (15129) Scientific Communication and Education (2045) Synthetic Biology (4290) Systems Biology (9817) Zoology (2269)