Professor University of Toronto Toronto, Ontario, Canada
Background/Question/Methods
Plant microbiomes can dramatically improve the fitness of their hosts, but some microbiomes are more or less beneficial than others. Partner specificity, the range and diversity of microbial partners with which a plant host interacts, likely both influences, and is influenced by, variation in microbial benefit to hosts. Specialisation may facilitate cooperative host-microbiome coevolution by increasing broad sense microbiome heritability; however, it is also subject to ecological risks when microbial partners are horizontally transmitted. My study examines how specificity will evolve in natural populations by measuring the relationship between host specificity and plant and microbe fitness. I measure variation in host specificity in Lemna minor (common duckweed), a small, clonally reproducing, floating aquatic plant in which different microbial communities vary in their fitness effect on plant genotypes. These interactions are often net mutualistic, with plants provisioning microbes with growth substrate, and microbiomes collectively promoting plant growth despite individual strains ranging from mutualistic to commensal to pathogenic. I inoculated a diverse assemblage of duckweed genotypes with a novel microbial community. Following inoculation, I assessed host fitness by measuring plant surface area, and measured benefit to microbes by assessing community abundance and composition via 16s rRNA sequencing, qPCR, and flow cytometry.
Results/Conclusions
Preliminary data indicate that host plants that “match” microbial communities (i.e. hosts and microbial that are collected from the same location), show higher host fitness measured by improved growth over a 14 day experimental period in a pilot project involving 3 host genotypes, than mismatches (i.e. hosts and microbes that are collected from disparate communities). Higher host fitness in matches indicates that hosts likely possess traits that help to promote the growth of microbial partners that are beneficial to a focal host, though further research is necessary in order to confirm this result and relate it to microbial growth. These preliminary results highlight that microbes play a key role in the fitness of this plant, despite being horizontally transmitted. Horizontal transmission, acquisition of microbes from a host’s external environment, is common in plant-microbe interactions. Therefore, these results suggest that plant local adaptation to microbial communities may be common across ecological systems
