Fig. 2.

From phenomes to host/microbe fitnesses. The diagram shows how our models connect collections of traits (i.e., phenomes) of microbes to host fitness and microbe fitness. a When HS is acting, each trait (represented by a triangle) has a fitness score affecting host fitness (red − 1, green + 1, blue 0). We determined the host absolute fitness and relative fitness with the average fitness score of all microbial traits associated with its microbiome and a host selection coefficient (see “Methods” for details). b When TMS/HMS is acting, each trait has another fitness score that affects microbe fitness (red − 1, green + 1, blue 0). The difference between HMS and TMS is that the fitness score of a certain trait is universal for all hosts under TMS but varies from host to host under HMS. Similarly, microbial absolute fitness and relative fitness are also determined with the average fitness score of all microbial traits possessed by the microbe and a microbial selection coefficient (see “Methods” for details)