Fig. 1

Host reproduction and microbial community assembly under models of selection. a A schematic showing the action of host selection on numbers of offspring. Each small circle represents a host with the first row representing the parental host population and the second row representing the offspring host population. The color indicates the fitness status of hosts which is completely determined by the microbes hosts carry (blue, fit; red, unfit), and the dotted lines indicate the parent-offspring relationship between generations. Fitter hosts produce relatively more offspring, weighted by parental fitness. b The relative abundance of microbial OTUs in host offspring, taking account of microbial fitness values. The letters “P,” “E,” “S,” and “O” stand for parental, environmental, source, and offspring microbial communities, respectively. The values of Y% and X% represent the percentage of host contribution under mixed environment (ME), and the percentage of parental inheritance under mixed acquisition (MA), respectively. Two yellow ellipses represent the source community (either parental, environmental, or mixed microbiomes depending on the value of X), and the offspring microbiome with a blue arrow indicating how microbes are sampled. Each small circle stands for a microbe with its color indicating the fitness status (green, fit; red, unfit but abundant in source community; blue, unfit and rare in source community). Fitter microbes and abundant microbes are more likely to be acquired by offspring