Spatial heterogeneity in genetic diversity and composition of bacterial symbionts in a single host species population

Abstract

Revealing genetic diversity in a root nodulation symbiosis under field conditions is critical to understand the formation of ecological communities of organisms associated with hosts and the nitrogen cycle in natural ecosystems. However, our knowledge of genetic diversity of bacterial mutualists on a local scale is still poor because of the assumption that the genetic diversity of mutualistic bacteria is constrained by their hosts. MethodsWe thoroughly investigated genetic diversity of Frankia in a local forest stand. We collected root nodules from 213 Alnus hirsuta seedlings covering the spatial range of the continuous population, which means that Alnus individuals occurred in a relatively homogeneous distribution in a continuous forest. Then, a phylogenetic analysis was performed for the nifD-K IGS region, including global Frankia sequences from Alnus hosts. ResultsThe genetic diversity of Frankia detected even on a local scale measured as high as that shown by previous studies conducted on a regional scale. Moreover, a genetic structure analysis revealed a spatially mosaic-like distribution of genetic variation in Frankia despite the small spatial scale. Conclusions 3The genetic diversity and composition of bacterial mutualists are heterogeneous on a local scale. Our findings demonstrate that genetically different bacterial symbionts simultaneously interact with a single host population and interaction partnerships spatially vary. The standing variation could produce dynamic ecological and evolutionary outcomes in a heterogeneous forest ecosystem.

High Frankia abundance and low diversity of microbial community are associated with nodulation specificity and stability of sea buckthorn root nodule

“…EAN1pec abundance in soil ( Tekaya et al., 2018 ). The coexistence of the dominant Frankia strain with multiple low-abundance Frankia strains may be due to the fact that the multiple functions of genetically diverse Frankia can complement each other to improve the overall fitness of host plants in complex ecosystems ( Kagiya and Utsumi, 2020 ). In addition to Frankia , we discovered non- Frankia microorganisms in sea buckthorn RN ( Figure 4 ).…”