Box 1: The tenets of natural selection applied to microbe-mediated adaptation
The phenotype of an organism is fundamental to local adaptation and adaptive plasticity because natural selection acts upon traits (or selection acts upon plasticity in traits). Evolution by natural selection will occur when the following criteria are met (Lewontin 1970):
  1. Variation exists in host traits that mediate or respond to interactions with specific microbes or microbial communities, which leads to different host genotypes associating with or responding to different microbes.
  2. Host traits that mediate interactions with microbes are heritable
  3. Traits mediating interactions with specific microbes or microbial communities affect fitness.