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In #PopulationGenetics there’s the idea of minimum viable population. Is there a similar idea/equation in #Linguistics ? As in the minimum number of speakers of a language before the language disappears? @linguistics
Our new #preprint changes the way we look at an “extinction vortex” in which a small population loses fitness, causing it to become even smaller https://www.biorxiv.org/content/10.1101/2024.10.25.620329v1.
#MutationalMeltdown #EffectivePopulationSize #EvolutionaryRescue #PopulationGenetics #EvolGenPaper @wmawass @jdmatheson @uliseshmc 1/7
bioRxiv · Extinction vortices are driven more by a shortage of beneficial mutations than by deleterious mutation accumulationNatural populations are increasingly at risk of extinction due to climate change and habitat loss and fragmentation. The long-term viability of small populations can be threatened by an extinction vortex a positive feedback loop between declining fitness and declining population size. Two distinct mechanisms can drive an extinction vortex: i) ineffective selection in small populations allows deleterious mutations to fix, driving mutational meltdown, and ii) fewer individuals produce fewer of the novel beneficial mutations essential for long-term adaptation, a mechanism we term mutational drought. We measure the relative importance of each mechanism, on the basis of how sensitive beneficial vs. deleterious components of fitness flux are to changes in census population size near the critical population size at which fitness is stable. We derive analytical results given linkage equilibrium, complemented by simulations that capture the complex linkage disequilibria that emerge under high deleterious mutation rates. Even in the absence of environmental change, mutational drought can be nearly as important as mutational meltdown. Real populations must also adapt to a changing environment, making mutational drought more important. A partial exception is that mutational drought is somewhat less important when the beneficial mutation rate is high, although its contribution remains substantial. The critical population size is driven substantially higher by linkage disequilibria between deleterious and beneficial mutations, which also increase (albeit modestly) the importance of mutational drought.
Our latest paper https://elifesciences.org/articles/87335
directly measures the #EffectivePopulationSize that matters to #NearlyNeutralTheory / #DriftBarrier theory, as the degree to which #CodonBias differs from expectations from GC content. Surprisingly, stronger #NaturalSelection -> higher #IntrinsicStructuralDisorder proteins
#MolecularEvolution #PopulationGenetics #EvolgenPaper 1/
eLifeThe protein domains of vertebrate species in which selection is more effective have greater intrinsic structural disorderProteins evolve more intrinsic structural disorder under more effective selection, with selection assessed via a novel metric of codon adaptation.
Our extensively revised preprint now goes beyond clarifying Haldane’s arguments about the #CostOfSelection / #SubstitutionalLoad / #SelectiveDeaths, it also significantly extends them, and applies the resulting model to data https://www.biorxiv.org/content/10.1101/2021.11.01.466728v2
@jdmatheson @moi #EvolgenPaper #PopulationGenetics #NaturalSelection #FitnessComponents #GeneticLoad 1/10
bioRxiv · The cost of selection in selective deaths paid out of reproductive excessHaldane’s Dilemma refers to the concern that the need for many “selective deaths” to complete a substitution (i.e. selective sweep) creates a speed limit to adaptation. However, discussion of this concern has been marked by confusion over which features of adaptation produce speed limits, what those limits are, and the consequences of violating speed limits. The term “substitution load” has been particularly unhelpful in this regard. Here we distinguish different historical lines of reasoning that lead to speed limits. We identify one line of reasoning, focused on finite reproductive excess, that has not yet been fully addressed. We develop this into a more general theoretical model that can apply to populations with any life history, even those for which a generation or even an individual are not well defined. We then apply this model to a dataset measuring survival of 517 different genotypes of Arabidopsis thaliana grown in eight different environmental conditions. These data suggest highly permissive limits to the speed of adaptation in all environmental conditions. This is because a much higher proportion of deaths contribute to adaptation than were anticipated during historical discussions of speed limits.
### Competing Interest Statement
The authors have declared no competing interest.
Biologist currently studying #WolfSpiders, #PocketGophers, #BumbleBees #Shrews, the wildflower genus Anemone, and #CrawfishFrogs--mostly using population genetic techniques.
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#PopulationGenetics
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Intro post: I'm a professor of #Biology at the #UniversityOfWashington. My training is in #EvolutionaryBiology, #BehavioralEcology, #PopulationGenetics, and #Epidemiology. I did lots of work in #Bibliometrics and #NetworkTheory. I teach #DataLiteracy. These days I spend a lot of time thinking about the spread of #Misinformation, the #ScienceOfScience, and #PhilosophyOfScience. I do a lot of #BirdPhotography and love #ravens, #crows, and all #corvids.
For your trouble, here's a perfect crow.
