Nature 467, 587-590 (30 September 2010) | doi:10.1038/nature09352;
Received 5 April 2010; Accepted 15 July 2010; Published online 15 September 2010
Genome-wide analysis of a long-term evolution experiment with Drosophila
Molly K. Burke1, Joseph P. Dunham2, Parvin Shahrestani1, Kevin R. Thornton1, Michael R. Rose1 & Anthony D. Long1
1. Ecology and Evolutionary Biology, University of California, Irvine, 321 Steinhaus Hall, Irvine, California 92697-2525, USA
2. Molecular and Computational Biology, University of Southern California; Los Angeles, California 90098, USA
Correspondence to: Molly K. Burke1 Email: burkem@uci.edu
Correspondence to: Anthony D. Long1 Email: tdlong@uci.edu
Drosophila melanogaster (Science Daily)
Abstract
Experimental evolution systems allow the genomic study of adaptation, and so far this has been done primarily in asexual systems with small genomes, such as bacteria and yeast1,2, 3. Here we present whole-genome resequencing data from Drosophila melanogaster populations that have experienced over 600 generations of laboratory selection for accelerated development. Flies in these selected populations develop from egg to adult ~20% faster than flies of ancestral control populations, and have evolved a number of other correlated phenotypes. On the basis of 688,520 intermediate-frequency, high-quality single nucleotide polymorphisms, we identify several dozen genomic regions that show strong allele frequency differentiation between a pooled sample of five replicate populations selected for accelerated development and pooled controls. On the basis of resequencing data from a single replicate population with accelerated development, as well as single nucleotide polymorphism data from individual flies from each replicate population, we infer little allele frequency differentiation between replicate populations within a selection treatment. Signatures of selection are qualitatively different than what has been observed in asexual species; in our sexual populations, adaptation is not associated with ‘classic’ sweeps whereby newly arising, unconditionally advantageous mutations become fixed. More parsimonious explanations include ‘incomplete’ sweep models, in which mutations have not had enough time to fix, and ‘soft’ sweep models, in which selection acts on pre-existing, common genetic variants. We conclude that, at least for life history characters such as development time, unconditionally advantageous alleles rarely arise, are associated with small net fitness gains or cannot fix because selection coefficients change over time.
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NOTA CAUSTICANTE DESTE BLOGGER:
As experiências com as Drosophila melanogaster são muito importantes para o avanço da ciência e o bem-estar da humanidade. Contudo, após 100 anos de torturas em laboratórios, as Drosophila melanogaster teimam continuar sendo Drosophila melanogaster, e com um agravante: o tipo de torturas que elas sofrem em laboratórios científicos no mundo inteiro, elas nunca sofreram na natureza.
QED:
"at least for life history characters such as development time, unconditionally advantageous alleles rarely arise, are associated with small net fitness gains or cannot fix because selection coefficients change over time."
Traduzindo em graúdos: a Drosophila melanogaster vai continuar sendo Drosophila melanogaster nem que Darwin tussa.
Mais contundente foi o parágrafo final desta pesquisa de 35 anos e 600 gerações de Drosophila melanogaster:
"Our work provides a new perspective on the genetic basis of adaptation. Despite decades of sustained selection in relatively small, sexually reproducing laboratory populations, selection did not lead to the fixation of newly arising unconditionally advantageous alleles. This is notable because in wild populations we expect the strength of natural selection to be less intense and the environment unlikely to remain constant for ~600 generations.
Consequently, the probability of fixation in wild populations should be even lower than its likelihood in these experiments. This suggests that selection does not readily expunge genetic variation in sexual populations, a finding which in turn should motivate efforts to discover why this is seemingly the case."
Mais contundente foi o parágrafo final desta pesquisa de 35 anos e 600 gerações de Drosophila melanogaster:
"Our work provides a new perspective on the genetic basis of adaptation. Despite decades of sustained selection in relatively small, sexually reproducing laboratory populations, selection did not lead to the fixation of newly arising unconditionally advantageous alleles. This is notable because in wild populations we expect the strength of natural selection to be less intense and the environment unlikely to remain constant for ~600 generations.
Consequently, the probability of fixation in wild populations should be even lower than its likelihood in these experiments. This suggests that selection does not readily expunge genetic variation in sexual populations, a finding which in turn should motivate efforts to discover why this is seemingly the case."
Fui, nem sei por que, pensando, mas em ciência também se corre muito atrás do vento... especialmente vento macroevolutivo...
Coitadinhas das Drosophila melanogaster -- nem sob torturas excruciantes se sujeitaram corroborar o fato, Fato, FATO da evolução no contexto de justificação teórica...
Coitadinhas das Drosophila melanogaster -- nem sob torturas excruciantes se sujeitaram corroborar o fato, Fato, FATO da evolução no contexto de justificação teórica...
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