Data from: Disentangling direct and indirect fitness effects of microbial dormancy

Disentangling individual selection from kin selection is one of the greatest challenges of evolutionary biology. Even solitary organisms that do not interact directly with conspecifics may interact indirectly with them through competition for resources. As a result, traits that appear to affect individual fitness alone can also modify the fitness of relatives nearby and thus may evolve partially through these cryptic indirect fitness effects. Here we develop a method to quantitatively separate direct and indirect fitness consequences when some microbes become dormant, while neighbors of the same genotype remain active. Dormant microbes typically survive stresses that kill metabolically active cells, but dormancy also has a social side effect, sparing resources that may be used by nondormant individuals for growth. In structured populations, spared resources may be preferentially consumed by nondormant clonemates, providing an indirect benefit. Without population structure, however, exploitation by a never-dormant competitor imposes an indirect fitness cost on dormant cells. Cryptic indirect fitness effects may play a significant role in the evolution of many ostensibly asocial traits.

将个体选择（individual selection）与亲缘选择（kin selection）加以拆解区分，是进化生物学领域最为艰巨的挑战之一。即便不与同种个体发生直接互动的独居生物，也可能通过资源竞争与同种个体产生间接互动。因此，那些看似仅影响个体自身适合度的性状，同样可能改变周边亲缘个体的适合度，进而可通过这类隐蔽的间接适合度效应实现部分演化。本研究开发了一种定量分离直接与间接适合度效应的方法，该方法适用于部分微生物进入休眠状态、而同基因型的邻近个体仍保持代谢活性的场景。休眠微生物通常可在杀伤代谢活跃细胞的胁迫环境中存活，但休眠同时还存在一项社会性副作用：留存下可供非休眠个体用于增殖的资源。在具有种群结构的群体中，留存的资源可能优先被非休眠的克隆同伴消耗，从而带来间接收益。但在无种群结构的环境中，永不休眠的竞争者对资源的利用，会给休眠细胞带来间接适合度成本。这类隐蔽的间接适合度效应，或许在诸多表面上看似非社会性的性状演化中发挥了重要作用。