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 --- 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. --- ### 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...众多微生物彼此间存在相互作用，但在自然环境中直接观测这些相互作用难度极大，使得解析其适应性价值的过程颇为复杂。 社会性变形虫盘基网柄菌（Dictyostelium discoideum）会形成聚集体，其中部分细胞会为了其他细胞的存活而牺牲自身。在包含多个无关谱系的嵌合聚集体中，欺骗型个体可通过减少自身贡献来获取竞争优势，但野生型盘基网柄菌在多大程度上演化出了欺骗适应性，目前仍未完全明晰。本研究中，我们在不存在嵌合聚集体中欺骗或抗欺骗选择压力的环境下，对盘基网柄菌进行了实验演化。在此环境中培养的盘基网柄菌菌株，其在嵌合聚集体内的竞争能力出现下降，同时蛞蝓期（slug stage）的迁移能力也有所降低。与之相反，我们未观察到细胞数量这一未放松选择压力的性状出现下降。实验室条件下不再需要的性状出现退化，这一现象表明…… 本数据集包含了在放松选择压力下进行实验演化前后，盘基网柄菌菌株多种表型的测定结果。 完整实验方法详见研究论文，简要流程如下： 欺骗性测定：将目标菌株与标记型对照菌株以1:1的比例混合，铺于无营养培养基的滤纸上，诱导形成嵌合子实体。收集子实体后重悬于缓冲液中，利用明场与荧光显微镜进行成像，计算荧光标记孢子所占比例。 蛞蝓迁移测定：将目标菌株沿无营养培养基平板一端的割线接种，用不透明铝箔覆盖平板，仅保留平板另一端的一个小孔以允许光线入射。培养8天后对平板成像，测量每个子实体距接种起始线的距离。 细胞计数/孢子计数/孢子形成效率测定：将目标菌株接种于培养基平板，待其生长发育后对细胞数量进行定量…… # 放松选择压力下实验演化的盘基网柄菌表型测定 --- 本数据集包含对实验演化后的盘基网柄菌菌株开展的5种不同测定。10株野生型盘基网柄菌菌株在完全不发生社会周期的条件下进行演化（每个菌株设置3个重复株系）。实验演化结束后，研究者对演化后的菌株的多种性状进行测定，并与其祖先菌株进行对比。核心预测为：受到放松选择压力的性状（如蛞蝓迁移能力与欺骗性）会趋于退化，而在实验室环境中仍处于选择压力下的性状（如细胞数量）则不会出现退化。 ## 数据与文件结构说明 本数据集包含4个电子表格，对应5种不同的测定实验。 --- ### data_cheatingassay: 该数据集包含以1:1比例混合的盘基网柄菌菌株组合所形成的嵌合子实体中，荧光标记孢子与总孢子的数量……