A microscopic model of evolution of recombination

Bagnoli, Franco; Guardiani, Carlo

doi:10.1016/j.physa.2004.08.067

Cited by 6 publications

(7 citation statements)

References 29 publications

(43 reference statements)

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“…As a comparison, this finding does not hold when a non-recombinant population is in competition with a recombinant one [24], consistent with the fact that the genome of non-recombinant organisms is much shorter than that of recombinant ones.…”

Section: Discussionsupporting

confidence: 53%

A model of sympatric speciation through assortative mating

Bagnoli

Guardiani²

2005

Physica A: Statistical Mechanics and its Applications

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A microscopic model is developed, within the frame of the theory of quantitative traits, to study the combined effect of competition and assortativity on the sympatric speciation process, i.e. speciation in the absence of geographical barriers. Two components of fitness are considered: a static one that describes adaptation to environmental factors not related to the population itself, and a dynamic one that accounts for interactions between organisms, e.g. competition. A simulated annealing technique was applied in order to speed up simulations. The simulations show that both in the case of flat and steep static fitness landscapes, competition and assortativity do exert a synergistic effect on speciation. We also show that competition acts as a stabilizing force against extinction due to random sampling in a finite population. Finally, evidence is shown that speciation can be seen as a phase transition. The problem.The notion of speciation in biology refers to the splitting of an original species into two fertile, yet reproductively isolated strains. The allopatric theory, which is currently accepted by the majority of biologists, claims that a geographic barrier is needed in order to break the gene flow so as to allow two strains to evolve a complete reproductive isolation. On the other hand, many evidences and experimental data have been reported in recent years strongly suggesting the possibility of a sympatric mechanism of speciation. For example, the comparison of mythocondrial DNA sequences of cytochrome b performed by Schlieven and others [1], showed the monophyletic origin of cichlid species living in some volcanic lakes of western Africa. The main features of these lakes are the environmental homogeneity and the absence of microgeographical barriers. It is thus possible that the present diversity is the result of several events of sympatric speciation. An increasing number of studies referring both to animal and plant species lend further support to this hypothesis [2,3,4,5,6,7,8,9].The key element for sympatric speciation is assortative mating that is, mating must be allowed only between individuals whose phenotypic distance does not exceed a given threshold. In * Electronic address: franco.bagnoli@unifi.it † Electronic address: carlo@dma.unifi.it 1 fact, consider a population characterized by a bimodal distribution for an ecological character determining adaptation to the environment: in a regime of random mating the crossings between individuals of the two humps will produce intermediate phenotypes so that the distribution will never split. Two interesting theories have been developed to explain the evolution of assortativity. In Kondrashov and Kondrashov's theory [10] disruptive selection (for instance determined by a bimodal resource distribution) splits the population in two distinct ecological types that are later stabilized by the evolution of assortative mating. The theory of evolutionary branching developed by Doebeli and Dieckmann [11] is more general in that it does not require dis...

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Section: Discussionsupporting

confidence: 53%

A model of sympatric speciation through assortative mating

Bagnoli

Guardiani²

2005

Physica A: Statistical Mechanics and its Applications

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“…This has the effect of maintaining genetic and phenotypic diversity, without the risk associated with a high mutation rate: the generation of unviable offspring, that lead to the error threshold or to the mutation meltdown, Section 3.3. This genetic diversity is useful in colonizing new environments or for variable ones [29], but is essential to escape the exploitation from parasites, that reproduce (and therefore evolve) faster than large animals and plants [30].…”

Section: Evolution and Optimization Replicator Equationmentioning

confidence: 99%

“…(28), that if G a (Eq. (29)) is larger than the threshold G c (Eq. (28)), several quasispecies coexist, otherwise only the master sequence quasi-species survives.…”

Section: Speciation and Mutational Meltdown In The Hypercubic Genotypmentioning

confidence: 99%

Evolutionary Models for Simple Biosystems

Bagnoli

2009

Handbook on Biological Networks

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The concept of evolutionary development of structures constituted a real revolution in biology: it was possible to understand how the very complex structures of life can arise in an out-of-equilibrium system. The investigation of such systems has shown that indeed, systems under a flux of energy or matter can self-organize into complex patterns, think for instance to Rayleigh-Bernard convection, Liesegang rings, patterns formed by granular systems under shear. Following this line, one could characterize life as a state of matter, characterized by the slow, continuous process that we call evolution. In this paper we try to identify the organizational level of life, that spans several orders of magnitude from the elementary constituents to whole ecosystems.Although similar structures can be found in other contexts like ideas (memes) in neural systems and self-replicating elements (computer viruses, worms, etc.) in computer systems, we shall concentrate on biological evolutionary structure, and try to put into evidence the role and the emergence of network structure in such systems.1 Many larger complexes are formed by more that just one protein, and some protein need the help of other enzymes to stabilize the three-dimensional shape with covalent bonds or to add metals ions, sugar chains and other elements.2 Actually, in archea, too, there are introns, and also in bacteria self-splicing portions of RNA are present.

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“…This has been recently reformulated and revised by Burt [ 55 ] and Otto and Lenormand [ 56 ]. Bagnoli and Guardiani have proposed a “microscopic model,” which “provides a high velocity of movement in the phenotypic space” [ 57 ]. Cavalier-Smith, however, suggests that the recombination caused by sex is an incidental consequence of crossing over, rather than the main selective advantage for the origin of sex [ 25 ].…”

Section: Introductionmentioning

confidence: 99%

“…But this does not mean that all the authors base their proposals on a single type of cause. Among genetic studies, the following passage is meaningful: “cell fusion, in fact, doubling the cell food storage greatly increases the survival probability”; but then “even if syngamy originally evolved for trophic reasons, on the long run, sex fixed in populations due to the several advantages of gene mixing” [ 57 , page 491]. And among the works professing “other causes,” is this contribution by Cavalier-Smith: “the prime role (of syngamy) was twofold: to make zygotes larger and to increase their survival rate by being able to store more solid food reserves; to provide genetic redundancy in the dormant cysts so that accidental damage […] could be repaired by homologous recombination among genomes” [ 27 , page 46].…”

Section: Introductionmentioning

confidence: 99%

A Short-Term Advantage for Syngamy in the Origin of Eukaryotic Sex: Effects of Cell Fusion on Cell Cycle Duration and Other Effects Related to the Duration of the Cell Cycle—Relationship between Cell Growth Curve and the Optimal Size of the Species, and Circadian Cell Cycle in Photosynthetic Unicellular Organisms

Quintana¹,

Quintana²

2012

International Journal of Evolutionary Biology

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The origin of sex is becoming a vexatious issue for Evolutionary Biology. Numerous hypotheses have been proposed, based on the genetic effects of sex, on trophic effects or on the formation of cysts and syncytia. Our approach addresses the change in cell cycle duration which would cause cell fusion. Several results are obtained through graphical and mathematical analysis and computer simulations. (1) In poor environments, cell fusion would be an advantageous strategy, as fusion between cells of different size shortens the cycle of the smaller cell (relative to the asexual cycle), and the majority of mergers would occur between cells of different sizes. (2) The easiest-to-evolve regulation of cell proliferation (sexual/asexual) would be by modifying the checkpoints of the cell cycle. (3) A regulation of this kind would have required the existence of the G2 phase, and sex could thus be the cause of the appearance of this phase. Regarding cell cycle, (4) the exponential curve is the only cell growth curve that has no effect on the optimal cell size in unicellular species; (5) the existence of a plateau with no growth at the end of the cell cycle explains the circadian cell cycle observed in unicellular algae.

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A microscopic model of evolution of recombination

Cited by 6 publications

References 29 publications

A model of sympatric speciation through assortative mating

A model of sympatric speciation through assortative mating

Evolutionary Models for Simple Biosystems

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