Distinction between serpentine and non-serpentine AMF indicates role for edaphic selection in community assembly

Background/Question/Methods

Serpentine soil generates distinct plant assemblages, but it is not known if serpentine effects arbuscular mycorrhizal fungal (AMF) assembly or how this may contribute to plant adaptation to serpentine.  A previous study showed that serpentine and non-serpentine adapted ecotypes of Collinisa sparsiflora associated with distinct AMF assemblages.  A related study showed the distinction was not due to host-fungal preference.  This study tests if the distinction between plant ecotype AMF assemblages was due to edaphic factors shaping distinct serpentine and non-serpentine AMF assemblages. We sampled non-C. sparsiflora plant roots from five serpentine and five non-serpentine sites in close proximity (50 m – 150 m between sites) and identified AMF associated with the root samples by amplification of rDNA using AMF specific primers, cloning, and sequencing.  We also identified the plant species associated with the root samples by amplification of intergenic spacer region between the trnL (UAA) 3’ exon and trnF (GAA) gene, cloning, and sequencing to use as a covariant for statistical analysis.  We sequenced a total of 1,071 AMF clones, and 664 plant clones from 40 root samples (4 from each site), and used a combination of sequence similarity and phylogenetic analysis to determine AMF and plant operational taxonomic units (OTUs).  We used Bray-Curtis similarity, multidimensional scaling, and analysis of similarity to compare root sample AMF and plant assemblages.  We use multivariate variance partitioning analysis and Mantel tests to compare AMF and plant assemblages and measure the relative contribution of plant and soil factors on AMF assembly.

Results/Conclusions

Analyses clearly showed that serpentine and non-serpentine AMF assemblages are distinct – with the complete absence of the non-serpentine dominant AMF taxon on serpentine. These results indicate strong edaphic selection of serpentine tolerant/adapted AMF taxa in serpentine soil and confirm a strong ecological relationship between AMF and plant tolerance to serpentine soil.