Welwitschia mirabilis is an ancient and rare plant distributed along the western coast of
Namibia and Angola. Several aspects of Welwitschia biology and ecology have been investigated,
but very little is known about the microbial communities associated with this plant.
This study reports on the bacterial and fungal communities inhabiting the rhizosphere ofW.
mirabilis and the surrounding bulk soil. Rhizosphere communities were dominated by
sequences of Alphaproteobacteria and Euromycetes, while Actinobacteria, Alphaproteobacteria,
and fungi of the class Dothideomycetes jointly dominated bulk soil communities.
Although microbial communities within the rhizosphere and soil samples were highly variable,
very few “species” (OTUs defined at a 97% identity cut-off) were shared between
these two environments. There was a small ‘core’ rhizosphere bacterial community (formed
by Nitratireductor, Steroidobacter, Pseudonocardia and three Phylobacteriaceae) that
together with Rhizophagus, an arbuscular mycorrhizal fungus, and other putative plant
growth-promoting microbes may interact synergistically to promote Welwitschia growth.
S1 Fig. Welwitschia plants dotted across an arid landscape (left). The exposed radial root system
of a Welwitschia plant (right).
S2 Fig. Rarefaction curves. a) bacteria, b) fungi. Sample nomenclature is as in S1 Table.
S3 Fig. Bar graph showing the phylum-level distribution of (a) bacterial and (b) fungal
OTUs (97% cutoff). The taxonomic affiliation was performed using the Ribosomal Database
Project Classifier (bacteria) and the UNITE database (fungi).
S4 Fig. Venn diagram showing the number of shared phylotypes observed between the rhizosphere
samples. a) bacteria, b) fungi. Sample nomenclature is as in S1 Table.
S1 Table. Bacterial diversity. Sample nomenclature indicates the sample type (S = bulk soil;
R = rhizosphere), replicate (S = 1 to 5, R = 1 to 3) and pseudoreplicate (a, b).
S2 Table. Fungal diversity. Sample nomenclature is as in S1 Table.