Friday, September 30, 2016

Extending evolutionary theory? - Russell Lande

I will be attending the Royal Society Meeting on New trends in evolutionary biology: biological, philosophical and social science perspectives. I'll post each of the abstracts and ask for your help in deciding what question to pose to the speakers. Here's the abstract for Russell Lande's talk on Evolution of phenotypic plasticity.

The scope and relative rates of adaptive phenotypic change from plasticity versus standard Darwinian evolution adaptive genetic changes depend on the time scale and the range of phenotypic alteration being considered. This distinction becomes blurred when plasticity itself evolves. Using standard methods from neo-Darwinian population genetic theory, I review recent models on the evolution of phenotypic plasticity in changing environments, emphasising the roles of environmental predictability and costs of plasticity in constant and labile characters. Adaptation to a novel environment may often occur by rapid evolution of increased plasticity followed by slow genetic assimilation of the new phenotype. I elucidate the connection between environmental tolerance and plasticity. The theory of evolution of phenotypic plasticity is an important extension to neo-Darwinism, but does not necessitate a major revision of its foundations. The same conclusion applies to epigenetic mechanisms including interactions between genes or tissues in development, and to transgenerational phenotypic effects such as somatic inheritance, maternal effects and DNA methylation.
I could ask this question ...
Imagine a small group of organisms that find themselves in a new environment. Let's assume they have a genome containing 10,000 genes. How do they select for increased phenotypic plasticity in order to better adapt to the new environment? Are all genes affected or just a small number that might increase fitness? Which genes acquire additional potentially beneficial alleles that were not present in the small population before it encountered the new environment and how does that mechanism work?


  1. Shorter: How does an organism evolve the ability to evolve?

  2. Russ is an outstanding evolutionary quantitative geneticist who habitually does important work. Here he is doing some theory to investigate how a phenotypic response to the environment itself evolves. This is related to C.H. Waddington's famous 1942 explanation of "genetic assimilation" where alleles are favored that have the right phenotype, ending with a situation where a plastic response is converted to a genetic response. See the Wikipedia page for genetic assimilation

    Russ's theory is within the framework of the existing evolutionary synthesis. I would expect him to be a voice of sanity at the meeting.

    1. Yep, I couldn't agree more. He's simply brilliant. And his career has been--it seems--to take key question/problems in biology and fit them into a evolutionary quant-gen framework. His work on plasticity, particularly the early paper with Via, is really terrific.

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  4. SOS response in bacteria ( comes to mind.

  5. Given that he wrote a book on the effects of stochasticity on population dynamics, I'd be surprised if he hasn't thought about these issues, even if it's not mentioned in the abstract.

  6. I'm not familiar with Lande's work. Most of what I know about the area comes from this review article by S A Frank.
    Natural selection. II. Developmental variability and evolutionary rate, J Evol Biol. 2011.
    There is a simple point that I think you're missing, or you wouldn't have asked your questions.

    By plasticity, I mean the variation between individuals which is not due to genetic differences. The simplest kind of plasticity is just noise. It could be a response to environmental noise. I will focus on a single real-valued trait q, so noise now means the non-genetic variance in q.

    In the original environment, the ideal value of q is q0, and the organisms have a regulatory system which produces values of q near q0, with a small variance. The original population is canalised: the regulatory system does a good job of shutting out the environmental noise. All of the small group of organisms that end up in the novel environment are genetically identical with respect to q.

    In the novel environment, the ideal value of q is q1, quite different from q0, and the organisms are struggling. Initially there are no alleles which effect the mean or variance of q. One possibility is a mutation which increases the variance of q, leaving the mean at q0 (or even moving a little way further from q1). This mutation increases plasticity. The key point is that it may increase fitness, because now some offspring have a value of q which is well suited to the new environment, whereas before there were none.