In the social amoeba Dictyostelium discoideum, shortened stalks may limit obligate cheater success even when exploitable partners are available

Cooperation is widespread across life, but its existence can be threatened by exploitation. The rise of obligate social cheaters that are incapable of contributing to a necessary cooperative function can lead to the loss of that function.  In the social amoeba Dictyostelium discoideum, obligate social cheaters cannot form dead stalk cells and in chimeras instead form living spore cells. This gives them a competitive advantage within chimeras. However, obligate cheaters of this kind have thusfar not been found in nature, probably because they are often enough in clonal populations that they need to retain the ability to produce stalks.  In this study we discovered an additional cost to obligate cheaters. Even when there are wild-type cells to parasitize, the chimeric fruiting bodies that result have shorter stalks and these are disadvantaged in spore dispersal.  The inability of obligate cheaters to form fruiting bodies when they are on their own combined with the lower functionality of ..., Strains and culture conditions 
To prepare food bacteria for D. discoideum clones to prey upon, we first spread non-pathogenic K. pneumoniae KpGe (Dicty Stock Center, dictybase.org) from stocks frozen in 80% KK2 [2.25 g KH2PO4 (Sigma-Aldrich) and 0.67 g K2HPO4 (Fisher Scientific) per liter] and 20% glycerol on an SM/5 agar media [2 g glucose (Fisher Scientific), 2 g yeast extract (Oxoid), 0.2 g MgCl2 (Fisher Scientific), 1.9 g KHPO4 (Sigma-Aldrich), 1 g K2HPO5 (Fisher Scientific), and 15 g agar (Fisher Scientific) per liter] and allowed the bacteria to grow at room temperature until colonies appeared. We picked a single colony with a sterile loop, spread it on a new SM/5 plate, and allowed the bacteria to proliferate. We collected these bacteria into KK2 with a sterile loop and diluted them to 1.5 OD600 in KK2 (~5 x 108 cells, measured with an Eppendorf BioPhotometer). We used these bacteria as food for amoebas in our experiment and repeated this process anew for each of the three repli..., , # Data from: In the social amoeba Dictyostelium discoideum, shortened stalks may limit obligate cheater success even when exploitable partners are available

[https://doi.org/10.5061/dryad.5dv41nsd3](https://doi.org/10.5061/dryad.5dv41nsd3)

These data represent an attempt to look for effects of the presence of obligate cheaters in Dictyostelium discoideum chimeras on resulting fruiting body stalk lengths. A cooperative strain (NC28.1) and an obligate cheater descendant (EC2) were combined in various proportions, allowed to fruit, and the resulting fruiting bodies were measured using microsophy.

## Description of the data and file structure

Filename: Medina2024datafinal.csv

Short description: Heights of fruiting bodies

**Column names:**

sampleDescription - Factor - a unique name for each sample

dateCollected - Factor - date of data collection

stalk_length - Number - length (in mm) of fruiting body stalks, measured via light microscopy

day - Factor - Each experiment w...