Here is my 2 cents. It is really hard to understand which features of the organism natural selection favors at any given time, even in controlled experiments where we can sequence everything and directly measure fitness, let alone in nature.
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One intuitive thought is that natural selection “tries to improve” suboptimal cellular modules. A previous paper by
@jireva and other works show that this happens at least sometimes. https://journals.plos.org/plosgenetics/article?rev=1&id=10.1371/journal.pgen.1007958 … But how good is natural selection at doing that?Prikaži ovu nit -
The problem is that there are likely multiple suboptimal modules, even in the simplest organisms like bacteria. Some modules can perhaps be improved by many large-effect mutations and other only by a few small-effect mutations. If so, which modules will be actually optimized?
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If modules were independent, all of them could be optimized simultaneously (with different rates). But if a population evolves in the clonal interference regime (which most microbial populations do), then natural selection many not be able to optimize all modules simultaneously.
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Instead, natural selection may “focus” on optimizing modules where large-effect mutations are available, while adaptation of other modules will “stall”. We characterized this phenomenon experimentally (hence, the title).
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Our work has two main implications. (1) Different modules are in fact improved by mutations with different fitness effects. This is not as trivial as it might sound, IMO. Would love to discuss more with anyone interested.
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Our work has two main implications. (2) It might be difficult for natural selection to bring all modules of a multi-modular organism to their respective optima, especially in a fluctuating environment.
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If you have any comments or thoughts on the ms, please respond here, or DM me, or send me an email. We look forward to any and all feedback.
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What I would love to know next: (1) How do the distributions of fitness and phenotypic effects of mutations look like for different cellular modules? Say, in simple lab conditions.
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What I'd love to know next: (2) How good is natural selection at optimizing these modules? E.g., how many modules/biological processes were suboptimal, say, at the beginning of the
@RELenski’s LTEE? And how many of them have reached physiological optimum after 70K of evolution?Prikaži ovu nit
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