Arbuscular mycorrhizal community assembly in the roots of two endangered and two common prairie plant species

Background/Question/Methods

Arbuscular mycorrhizal fungi (AMF) live symbiotically in the plant roots of approximately 80% of plant species.  Association with AMF provides plants with a variety of benefits, including increased access to nutrients and protection from pathogens. The degree of benefit has been shown to vary based on the particular plant species-AMF species pairing. A variety of studies have shown some degree of selectivity at work in the formation of root AMF communities. Therefore, better knowledge of the plant-AMF relationship may lead to improved methods in the maintenance and restoration of imperiled plant populations and may be a key to their conservation. We investigated the AMF community formed by two endangered plants, Erigeron decumbens var. decumbens and Lomatium bradshawii, and two common and widespread plants, Achillea millefolium and Prunella vulgaris. Plants were grown both individually and in a community of all four species in a sterile medium with additional field soil inoculum from a remnant prairie where all four plant species occur. After four months, roots were harvested and AMF root communities were assayed using molecular methods targeting large subunit ribosomal RNA gene sequences.

Results/Conclusions

The endangered species, L. bradshawii, had a lower overall colonization rate than the three other species (p<0.01). Both host species identity and the community context affected richness of the AMF root communities: P. vulgaris had the richest AMF communities (p<0.05), and growth in a community decreased per plant AMF richness (p<0.05). Host species identity affected AMF community composition in roots (p<0.05). Indicator species analysis showed three AMF types, all in the Archaeosporales, characteristically associated with P. vulgaris (p<0.05). Although we did not find any fungi uniquely associated with the two endangered plants, there was evidence for host species identity affecting AMF community composition in roots. These results are strong evidence that both partner selectivity and biotic context play a role in determining the composition of AMF communities.