Experimental evolution of Dictyostelium discoideum cheating under relaxed selection

Many microbes interact with one another, but the difficulty of directly observing these interactions in nature makes interpreting their adaptive value complicated.  The social amoeba Dictyostelium discoideum forms aggregates wherein some cells are sacrificed for the benefit of others. Within chimeric aggregates containing multiple unrelated lineages, cheaters can gain an advantage by undercontributing, but the extent to which wild D. discoideum has adapted to cheat is not fully clear. In this study, we experimentally evolved D. discoideum in an environment where there were no selective pressures to cheat or resist cheating in chimeras. D. discoideum lines grown in this environment evolved reduced competitiveness within chimeric aggregates and reduced ability to migrate during the slug stage. By contrast, we did not observe a reduction in cell number, a trait for which selection was not relaxed.  The observed loss of traits that our laboratory conditions had made irrelevant suggests that..., Data represent the results of assays measuring various phenotypes of D. discoideum strains before and after experimental evolution under relaxed selection.
See manuscript for full methods, but in short:
Cheating assays - combine strains of interest with labelled control strain at 50:50 ratio. Plate atop filter paper on non-nutrient plates, allow to form chimeric fruiting bodies.  Harvest fruiting bodies, suspend in buffer, and photograph using bright field and fluorescent microscopy. Calculate fraction of fluorescently labelled spores.
Slug migration assays - inoculate strains of interest along a secant line on one end of a non-nutrient plate. Cover in opaque foil except for a small hole that allows light from the opposite end of the plate. Wait 8 days, then photograph plates. Measure distance of each fruiting body from the starting line.
Cell count/spore count/sporulation efficiency assays - inoculate strains of interest on plates, wait for growth/development, and then quantify cells u..., , # Assays of phenotypes of D. discoideum experimentally evolved under relaxed selection

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Dataset represents five different assays performed on experimentally evolved D. discoideum lines. 10 wild D. discoideum strains were evolved (as three replicate lines each) under conditions in which the social cycle never occurred. After experimental evolution, the researchers measured various traits of the experimentally evolved lines and compared them to their ancestors. The chief prediction was that traits for which selection had been relaxed (like slug migration and cheating) should tend to decay, while traits that continued to be under selection in the lab (like cell number) should not.

## Description of the Data and file structure

The data are in four spreadsheets corresponding to five different assays.

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### data\_cheatingassay:

These data represent the number of fluorescently labelled and total spores within chimeric fruiting bodies inoculated from a 50:50 mixture of a D. disco...