Plant host identity and soil macronutrients explain little variation in sapling endophyte community composition: is disturbance an alternative explanation?

1. Bacterial endophytes may be fairly host specific; nonetheless, an important subset of taxa may be shared among numerous host species forming a community-wide core microbiome. Moreover, other key factors, particularly the supply of limiting macronutrients and disturbances, may supersede the importance of host identity. 2. We tested the following four non-mutually exclusive hypotheses: 1. The Host Identity Hypothesis: endophytes vary substantially among different host plant species. 2. The Core Microbiome Hypothesis: a subset of microbial taxa will be shared among all host plant species. 3. The Soil Resource Supply Hypothesis: endophytes vary substantially among habitats with experimentally elevated levels of macronutrients. 4. The Disturbance-Disruption Hypothesis: disturbances created by the periodic application of antibiotics structure bacterial endophyte communities. 3. We tested these hypotheses by characterizing endophytes using high-throughput sequencing among seedlings of f...