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

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.