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