Article

The theory of facilitated variation.

Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA.
Proceedings of the National Academy of Sciences (Impact Factor: 9.81). 06/2007; 104 Suppl 1:8582-9. DOI: 10.1073/pnas.0701035104
Source: PubMed

ABSTRACT This theory concerns the means by which animals generate phenotypic variation from genetic change. Most anatomical and physiological traits that have evolved since the Cambrian are, we propose, the result of regulatory changes in the usage of various members of a large set of conserved core components that function in development and physiology. Genetic change of the DNA sequences for regulatory elements of DNA, RNAs, and proteins leads to heritable regulatory change, which specifies new combinations of core components, operating in new amounts and states at new times and places in the animal. These new configurations of components comprise new traits. The number and kinds of regulatory changes needed for viable phenotypic variation are determined by the properties of the developmental and physiological processes in which core components serve, in particular by the processes' modularity, robustness, adaptability, capacity to engage in weak regulatory linkage, and exploratory behavior. These properties reduce the number of regulatory changes needed to generate viable selectable phenotypic variation, increase the variety of regulatory targets, reduce the lethality of genetic change, and increase the amount of genetic variation retained by a population. By such reductions and increases, the conserved core processes facilitate the generation of phenotypic variation, which selection thereafter converts to evolutionary and genetic change in the population. Thus, we call it a theory of facilitated phenotypic variation.

0 Bookmarks
 · 
110 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: It has long been known that temporally unstable environments are likely to promote the evolution of plastic adaptations, whilst it is equally clear that such adaptations are precisely those that characterize successful colonizers. These two established findings, however, are rarely related within a single framework. This article bridges this gap via the development of a very simple evolutionary algorithm that tracks both directional selection and the evolution of plasticity under various synthetic climatic regimes. The output of the model allows for the construction of a dispersal index that provides a measure of population-level dispersal potential under each particular climatic regime. The output thus establishes both the timing and extent of selection for plasticity and the consequences of that plasticity for the timing of probable dispersal events in the context of climatic instability. Results suggest that periods of low climatic instability abruptly following extended periods of higher climatic instability are particularly conducive to dispersal, leading to the formulation of the Accumulated Plasticity Hypothesis. These results, and the hypothesis they support, are discussed in relation to the varied manifestations of plasticity in biological systems and their relevance to human evolution.
    Adaptive Behavior 07/2014; 22(4):235-254. DOI:10.1177/1059712314533573 · 1.15 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The origin and evolution of multicellularity was directly investigated using experimental evolution. Using settling selection, multicellularity evolved quickly and repeatedly from a common unicellular ancestor, Baker's yeast. The transition occurred by persistent adhesion of daughter cells following cell replication. The resulting multicellular individuals had a morphology reminiscent of snowflakes, with many characteristics of extant multicellular species, including cell cell attachment, a single-cell bottleneck, and juvenile and adult life history stages. Cellular division of labor by apoptosis evolved in large snowflake clusters, ameliorating the effects of a trade-off between snowflake settling and growth rate. Continued settling selection led to additional adaptation, such as a more hydrodynamic cluster shape. The majority of the developmental changes that evolved after the transition to multicellularity were contingent on this transition and even on the specific mode of cluster formation. The origin and subsequent evolution of multicellular complexity in snowflake yeast can be directly attributed to natural selection.
    BioScience 04/2014; 64(5):383-393. DOI:10.1093/biosci/biu045 · 5.44 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Sexual selection acting on small initial differences in mating signals and mate preferences can enhance signal-preference co-divergence and reproductive isolation during speciation. However, the origin of initial differences in sexual traits remains unclear. We asked whether biotic environments, a source of variation in sexual traits, may provide a general solution to this problem. Specifically, we asked whether genetic variation in biotic environments provided by host plants can result in signal-preference phenotypic covariance in a host-specific, plant-feeding insect. We used a member of the Enchenopa binotata species complex of treehoppers (Hemiptera: Membracidae) to assess patterns of variation in male mating signals and female mate preferences induced by genetic variation in host plants. We employed a novel implementation of a quantitative genetics method, rearing field-collected treehoppers on a sample of naturally-occurring replicated host plant clone lines. We found remarkably high signal-preference covariance among host plant genotypes. Thus, genetic variation in biotic environments influences the sexual phenotypes of organisms living on those environment in a way that promotes assortative mating among environments. This consequence arises from conditions likely to be common in nature (phenotypic plasticity and variation in biotic environments). It therefore offers a general answer to how divergent sexual selection may begin.This article is protected by copyright. All rights reserved.
    Evolution 01/2015; DOI:10.1111/evo.12604 · 4.66 Impact Factor

Preview

Download
0 Downloads
Available from