Experimental Tests of the Roles of Adaptation, Chance, and History in Evolution

Travisano, Michael; Mongold, Judith A.; Bennett, Albert A.; Lenski, Richard E.

doi:10.1126/science.7809610

Cited by 435 publications

(459 citation statements)

References 20 publications

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“…Microbial experiments have shown that selection is usually the most important driver of evolutionary change relative to history and chance after at least 200 generations of evolution in a novel environment [23][24][25][26][27][28]. Similar results have been obtained in sexual and initially diverse experimental populations of Drosophila after 20-30 generations [29,30].…”

Section: Introductionsupporting

confidence: 73%

“…Each sum of squares estimate was divided by the sum of all estimates to obtain the relative contribution of each factor. We prefer this method to alternative variance component-based approaches [23,26,29] since our design does not permit a full additive partition of variation using these methods. Nevertheless, a variance component analysis of our data produced similar results.…”

Section: (C) Fitness Assaymentioning

confidence: 99%

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Repeatability of adaptation in experimental populations of different sizes

2015

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The degree to which evolutionary trajectories and outcomes are repeatable across independent populations depends on the relative contribution of selection, chance and history. Population size has been shown theoretically and empirically to affect the amount of variation that arises among independent populations adapting to the same environment. Here, we measure the contribution of selection, chance and history in different-sized experimental populations of the unicellular alga Chlamydomonas reinhardtii adapting to a high salt environment to determine which component of evolution is affected by population size. We find that adaptation to salt is repeatable at the fitness level in medium (N e ¼ 5 Â 10 4 ) and large (N e ¼ 4 Â 10 5 ) populations because of the large contribution of selection. Adaptation is not repeatable in small (N e ¼ 5 Â 10 3 ) populations because of large constraints from history. The threshold between stochastic and deterministic evolution in this case is therefore between effective population sizes of 10 3 and 10 4 . Our results indicate that diversity across populations is more likely to be maintained if they are small. Experimental outcomes in large populations are likely to be robust and can inform our predictions about outcomes in similar situations.

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Section: Introductionsupporting

confidence: 73%

Section: (C) Fitness Assaymentioning

confidence: 99%

Repeatability of adaptation in experimental populations of different sizes

2015

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“…The ¢tness reversion may be the more important e¡ect if the environment does not change but, if the environment should change, then the latent e¡ects of the original and compensatory mutations may be more important (e.g. Travisano et al 1994).…”

Section: Discussionmentioning

confidence: 99%

Pervasive compensatory adaptation inEscherichia coli

Moore

Rozen

Lenski

2000

Proc. R. Soc. Lond. B

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127

115

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To investigate compensatory adaptation (CA), we used genotypes of Escherichia coli which were identical except for one or two deleterious mutations. We compared CA for (i) deleterious mutations with large versus small e¡ects, (ii) genotypes carrying one versus two mutations, and (iii) pairs of deleterious mutations which interact in a multiplicative versus synergistic fashion. In all, we studied 14 di¡erent genotypes, plus a control strain which was not mutated. Most genotypes showed CA during 200 generations of experimental evolution, where we de¢ne CA as a ¢tness increase which is disproportionately large relative to that in evolving control lines, coupled with retention of the original deleterious mutation(s). We observed greater CA for mutations of large e¡ect than for those of small e¡ect, which can be explained by the greater bene¢t to recovery in severely handicapped genotypes given the dynamics of selection. The rates of CA were similar for double and single mutants whose initial ¢tnesses were approximately equal. CA was faster for synergistic than for multiplicative pairs, presumably because the marginal gain which results from CA for one of the component mutations is greater in that case. The most surprising result in our view, is that compensation should be so readily achieved in an organism which is haploid and has little genetic redundancy. This ¢nding suggests a degree of versatility in the E. coli genome which demands further study from both genetic and physiological perspectives.

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“…Diversity is the product of three fundamental evolutionary influences: adaptation, chance, and history (Travisano et al 1995a). There is an intense debate in biology regarding the role that each of these factors plays in the evolutionary trajectories of organisms (Conway Morris 2003, Gould and Lewontin 1979, Mayr 1983, Lauder 1981, 1982, and we can ask the same question regarding the evolutionary paths taken by different cultures.…”

Section: Historicitymentioning

confidence: 99%

On Vastness and Variability: Cultural Transmission, Historicity, and the Paleoindian Record in Eastern South America

Araújo

2015

An. Acad. Bras. Ciênc.

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Eastern South America, or what is today Brazilian territory, poses interesting questions about the early human occupation of the Americas. Three totally distinct and contemporaneous lithic technologies, dated between 11,000 and 10,000 14 C BP, are present in different portions of the country: the Umbu tradition in the south, with its formal bifacial industry, with well-retouched scrapers and bifacial points; the Itaparica tradition in the central-west / northwest, totally unifacial, whose only formal artifacts are limaces; and the "Lagoa Santa" industry, completely lacking any formal artifacts, composed mainly of small quartz flakes. Our data suggests that these differences are not related to subsistence or raw-material constraints, but rather to different cultural norms and transmission of strongly divergent chaînes opératoires. Such diversity in material culture, when viewed from a cultural transmission (CT) theory standpoint, seems at odds with a simple Clovis model as the origin of these three cultural traditions given the time elapsed since the first Clovis ages and the expected population structure of the early South American settlers.

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Experimental Tests of the Roles of Adaptation, Chance, and History in Evolution

Cited by 435 publications

References 20 publications

Repeatability of adaptation in experimental populations of different sizes

Repeatability of adaptation in experimental populations of different sizes

Pervasive compensatory adaptation inEscherichia coli

On Vastness and Variability: Cultural Transmission, Historicity, and the Paleoindian Record in Eastern South America

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