A quasispecies approach to the evolution of sexual replication in unicellular organisms

Emmanuel Tannenbaum, José F. Fontanari

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


This study develops a simplified model describing the evolutionary dynamics of a population composed of obligate sexually and asexually reproducing, unicellular organisms. The model assumes that the organisms have diploid genomes consisting of two chromosomes, and that the sexual organisms replicate by first dividing into haploid intermediates, which then combine with other haploids, followed by the normal mitotic division of the resulting diploid into two new daughter cells. We assume that the fitness landscape of the diploids is analogous to the single-fitness-peak approach often used in single-chromosome studies. That is, we assume a master chromosome that becomes defective with just one point mutation. The diploid fitness then depends on whether the genome has zero, one, or two copies of the master chromosome. We also assume that only pairs of haploids with a master chromosome are capable of combining so as to produce sexual diploid cells, and that this process is described by second-order kinetics. We find that, in a range of intermediate values of the replication fidelity, sexually reproducing cells can outcompete asexual ones, provided the initial abundance of sexual cells is above some threshold value. The range of values where sexual reproduction outcompetes asexual reproduction increases with decreasing replication rate and increasing population density. We critically evaluate a common approach, based on a group selection perspective, used to study the competition between populations and show its flaws in addressing the evolution of sex problem.

Original languageEnglish
Pages (from-to)53-65
Number of pages13
JournalTheory in Biosciences
Issue number1
StatePublished - 1 Mar 2008


  • Error threshold
  • Evolution of sex
  • Quasispecies model

ASJC Scopus subject areas

  • Statistics and Probability
  • Ecology, Evolution, Behavior and Systematics
  • Applied Mathematics


Dive into the research topics of 'A quasispecies approach to the evolution of sexual replication in unicellular organisms'. Together they form a unique fingerprint.

Cite this