Table 4 Frequency of Frankia sub-clades occurring in clones
derived from Alnus tenuifolia rhizosphere soils in mid succession
(dense Populus balsamifera forests) that were either
unfertilized, fertilized with N
(NH4NO3), or fertilized with P
(P2O5). P-values in bottom rows were
derived from Fisher’s exact test conducted for pairwise comparisons of a
priori interest.
FIGURE CAPTIONS
Figure 1. Maximum-likelihood (RAxML) phylogeny of Frankia soil
clones and reference sequences, and selected actinobacterial outgroups,
based on rIGS locus. ML analysis was conducted on an alignment
containing 811 positions across sequences from 559 E. coli clones
containing 16S-23S ribosomal intergenic spacer (rIGS) loci amplified
from Frankia found in six Alaskan soils. Reference sequences for
phylogenetic comparison included 57 rIGS sequences derived from
previously collected nodules in each Alaskan study site, and 58 publicly
available sequences from across the Frankia genus
(Ghodhbane-Gtari et al ., 2010), and 10 sequences from outgroup
taxa within the Actinomycetes. Branch labels represent percent bootstrap
support, out of 1000 replicates. For clarity, only branches with ≥70%
support are shown, except in special cases. Collapsed clades are labeled
according to canonical Frankia cluster, in the case of comparison
sequences, with letter_number indicators for sequences found only in
soils in the present study, or according to groupings previously
observed in nodules (‘AK AT clade’ in A. tenuifolia nodules, ‘AK
AV-infective’ in A. viridis nodules). Single branch labels
containing ‘RF’ represent previously collected A. tenuifolia nodules;
labels containing ‘soil’ or ‘BP1’ are single clones from the present
study.
Figure 2. Accumulation curves of Frankia OTUs (subclades based on
rIGS locus) occurring in clones derived from soils in: A) early
succession (Alnus tenuifolia stands) A. tenuifoliarhizospheres (red curve), late succession (Picea glauca forests)A. tenuifolia rhizospheres (green curve), or late succession
areas without A. tenuifolia (blue curve); B) A. tenuifoliarhizospheres in mid-succession Populus balsamifera forests that
were either unfertilized (red curve), fertilized with N
(NH4NO3) (green curve), or fertilized
with P (P2O5) (blue curve). Shaded area
around each curve represents 95% confidence intervals of estimated
richness.
FIGURE 1