Rare biosphere in cultivated Panax rhizosphere shows deterministic assembly and cross-plant similarity

Abstract

Revealing the ecological patterns of abundant and rare microbial subcommunities in rhizosphere of cultivated plant is critical for understanding plant–microbe interactions and the formation of functionally important rhizosphere microbiome. Based on rhizodeposit support effects and colonization priority effects, the present study outlined two disparate hypotheses predicting the more deterministic assembly of abundant (the “dominance-determinism” hypothesis) and rare subcommunities (the “rare-determinism” hypothesis), respectively. These hypotheses were tested using bacterial and fungal subcommunities in the rhizosphere of three cultivated Panax species (P. ginseng, P. quinquefolium, and P. notoginseng). In each plant species, the abundant and rare taxa exhibited different patterns of distribution and composition, but similar edaphic factors could explain their phylogenetic community variations. Network analysis indicated that the abundant taxa located in more central positions than the rare taxa, and the negative links mainly exhibited between abundant and rare taxa. Null model showed that stochastic and deterministic processes dominated the assembly of abundant (determinism: 11.97–45.30 %) and rare (determinism: 67.24–96.30 %) subcommunities, respectively. In addition, almost all members of the rhizosphere abundant taxa (> 89 %) were also highly abundant in corresponding bulk soil. Among the three Panax species, the rare taxa exhibited stronger taxonomic overlap and phylogenetic similarity compared to the abundant taxa. These results indicate that the assembly of abundant subcommunities in Panax rhizosphere is highly stochastic and may relate to the priority effects, whereas the rare taxa tend to be the results of plant selection and exhibit potentially evolutionary conservatism.

Keywords

• Rare bacteria
• Rare fungi
• Rhizosphere
• Coevolution
• Priority effects
• Deterministic process