Data from: Fine-scale spatial ecology drives kin selection relatedness among cooperating amoebae

Cooperation among microbes is important for traits as diverse as antibiotic resistance, pathogen virulence, and sporulation. The evolutionary stability of cooperation against “cheater” mutants depends critically on the extent to which microbes interact with genetically similar individuals. The causes of this genetic social structure in natural microbial systems, however, are unknown. Here we show that social structure among cooperative Dictyostelium amoebae is driven by the population ecology of colonization, growth, and dispersal acting at spatial scales as small as fruiting bodies themselves. Despite the fact that amoebae disperse while grazing, all it takes to create substantial genetic clonality within multicellular fruiting bodies is a few millimeters distance between the cells colonizing a feeding site. Even adjacent fruiting bodies can consist of different genotypes. Soil populations of amoebae are sparse and patchily distributed at millimeter scales. The fine-scale spatial structure of cells and genotypes can thus account for the otherwise unexplained high genetic uniformity of spores in fruiting bodies from natural substrates. These results show how a full understanding of microbial cooperation requires understanding ecology and social structure at the small spatial scales microbes themselves experience.

微生物间的合作对于抗生素抗性、病原菌毒力以及孢子形成等多种截然不同的性状均具有重要意义。针对‘欺骗者’突变体的合作进化稳定性，在极大程度上依赖于微生物与遗传相似个体发生互作的程度。然而，目前学界仍不清楚自然微生物系统中这种遗传社会结构的形成诱因。本研究发现，协作型盘基网柄菌（Dictyostelium）变形虫之间的社会结构，由定植、生长与扩散的种群生态学过程驱动，其作用的空间尺度甚至可小至子实体（fruiting bodies）本身。尽管变形虫在觅食过程中会发生扩散，但只要定植于同一觅食位点的细胞之间存在数毫米的间距，即可在多细胞子实体内形成显著的遗传克隆性。即便相邻的子实体，其遗传组成也可能存在差异。变形虫的土壤种群在毫米尺度下呈现稀疏且斑块状分布的特征。因此，细胞与基因型的精细空间结构，能够解释自然基质来源的子实体孢子为何会呈现出此前无法阐明的高度遗传一致性。上述研究结果表明，若要全面理解微生物合作现象，必须在微生物自身所感知的微小空间尺度上，同步研究其生态学过程与社会结构。