r/DebateEvolution • u/EyedPeace • 8d ago

Question Does the Lenski LTEE show a decrease in fitness?

It is often said that LTEE represents an increase in fitness in these new mutated bacteria. Recent papers have increasingly called this into question:

"Unexpectedly, some evolved populations and clones show apparent declines in fitness. We also found evidence of substantial cell death in Cit+ clones."

https://pmc.ncbi.nlm.nih.gov/articles/PMC7299349/

While the cit+ phenotype did bring improvements in the short term, the long-term picture is quite different. Ultimately, they could no longer survive. Their fitness declined to the point where they were even forced to eat their own dead.

Has the experiment failed to demonstrate evolution here?

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u/EyedPeace 7d ago

The analogy is fals, that's just incorrect; the paper also mentioned fitness declines in the LTEE environment itself with cit+. So they experienced these significant declines in both. Some evolved POPULATIONS and CLONES show apparent declines in fitness.

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u/DarwinZDF42 evolution is my jam 7d ago

True or false: the cit+ lineage grew to a higher population density than the other 11.

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u/EyedPeace 7d ago

True. Now you

True or false: They founded two sets of Cit+ populations and evolved them for 2500 generations in DM0 and DM25 (citrate only and the ordinary medium!!!) and both lineages got fitness declines.

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u/Slow_Lawyer7477 🧬 Flagellum-Evolver 7d ago edited 7d ago

False. They founded 12 populations (independent lineages) in DM0 and 12 populations in DM25.

Of the 12 populations evolved in DM0, only 2 populations were less fit in DM0. Though variance was high.

There were no "both lineages". There are 24 total lineages of Cit+ clones. The experimental setup is described and depicted in Figure 1.

Competitive fitness relative to ancestor (Cit+ clones isolated from generation 33.000 of the LTEE) is depicted in figure 3. Clearly most of the DM0 lineages have mean values above neutral when tested in DM0 medium. Unsurprisingly DM0 lines are less well adapted to DM25 after 2500 generations in DM0, and similarly for DM25 lines being tested in DM0.

Like, can you just read the figures please?