OTU generation methods captured consistent community patterns
across soil conditions
All three OTU generation methods consistently demonstrate that total
soil microeukaryotic community composition clearly differentiated based
on soil condition (wet or mesic-dry), but no pattern was detected in
relation to the presence of F. meleagris , as observable in nMDS
ordinations (Fig. 3). The observed separations were statistically
significant (p =0.001) as indicated by a marginal PERMANOVA test
(Table S4) and remained when the importance of rare OTUs was
down-weighted by square root transformation of relative abundances (Fig.
S6, Table S5). Similar to observations for the plant community (Fig. 2),
microeukaryotic community composition was more variable among samples in
wet soil conditions compared to mesic-dry soil conditions (Fig. 3).
Mesic-dry samples clustered closer together indicating that communities
were more similar across samples (Fig. 3). When analyzing fungal and
protist community composition separately, we observed the same
significant separation (p <0.001) based on soil
conditions (wet or mesic-dry), but not in relation to the presence ofF. meleagris (Fig. S7, Table S6). While still significant, the
separation is visually less distinct for the protist community based on
OTU_S and OTU_C (Fig. S7 d, f) compared to OTU_A (Fig. S7b). The
tight clustering of samples from mesic-dry conditions is recovered in
both fungal and protist communities (Fig. S7).
Overall, phylum-level taxonomic composition was also comparable across
the three OTU generation methods used (Fig. 4). Based on read abundance,
protist communities were dominated by the Ciliophora (Alveolata) in both
wet and mesic-dry soil conditions (Fig. 4a). The relative abundance of
Alveolata was slightly lower when communities were characterised using
OTU_C and OTU_S compared to the OTU_A dataset (Fig. S8). The
Rhizarian phyla Endomyxa, Phytomyxea, and Filosa were also observed in
both conditions and were more abundant when reads were clustered into
OTU_C and OTU_S compared to OTU_As (Fig. 4a). In wet conditions, a
larger proportion of reads within both Alveolata and Rhizaria could not
be identified at the phylum level highlighting the potential for future
studies of poorly known lineages at this site. The proportion of
Ciliophora was smaller in wet vs mesic-dry conditions. In both soil
conditions, Ascomycota was the most common fungal phylum, and together
with Basidiomycota, made up over half of the sequenced fungal community
in wet soil conditions (Fig. 4b). In mesic-dry soil conditions on the
other hand, Mortierellomycota made up a larger fraction of the reads,
around 30%. Sequences assigned to Glomeromycota, which encompass all
arbuscular mycorrhizal fungi, were rare at this site, despite known high
abundance based on spore counts (personal observations of S.E.S.).
Chytridiomycota were also more abundant in mesic-dry compared to wet
soil conditions, while Rozellomycota made up around 10% of the reads in
both conditions. Close to 20% of fungal OTUs remained unidentified at
phylum level across all three methods (Fig. 4b). Many of these
unidentified lineags cluster with Zoopagomycota, Kickxellomycota and
Rozellomycota in the fungal tree (Supplementary datafile 2).