DOI: 10.5061/dryad.37nh37f
title: Data from: Larger plants promote a greater diversity of symbiotic nitrogen-fixing soil bacteria associated with an Australian endemic legume

description: A major goal in microbial ecology is to understand the factors that
 structure bacterial communities across space and time. For microbes that
 are plant symbionts, community assembly processes can lead to either a
 positive or negative relationship between plant size or age and soil
 microbe diversity. Here, we evaluated the extent to which such
 relationships exist within a single legume species (Acacia acuminata) and
 their naturally occurring symbiotic nitrogen-fixing bacteria (rhizobia).
 2. We quantified the diversity of rhizobia that associate with A.
 acuminata trees of variable size spanning a large environmental gradient
 in southwest Australia (72 trees in 24 sites spread across ~300,000 km2),
 using metabarcoding. We modelled rhizobia diversity using 16S exact
 genetic variants, in a binomial multivariate statistical framework that
 controlled for climate and local soil characteristics. 3. We identified
 two major phylogenetic clades of rhizobia that associate with A.
 acuminata. Soil sampled at the base of larger Acacia trees contained a
 higher richness of rhizobia genetic variants. Each major clade responds
 differently to environmental factors (climate and soil characteristics),
 but the positive association between tree size and rhizobia genetic
 diversity was mainly driven by responses from one of the two clades.
 Overall tree size explained more variation than any other factor,
 resulting in a ~3-fold increase in total richness and clade diversity from
 the smallest to the largest trees. 4. Synthesis. Previous studies have
 shown that plant host species is important in structuring microbial soil
 communities in the rhizosphere. Our results show that host size or age
 within a single plant species can also structure diversity of at least one
 group of soil microbes. A positive relationship between plant host size
 and rhizobia diversity suggests that hosts may modify the niche space of
 their surrounding soil (niche construction hypothesis) enabling a higher
 richness of microbial taxa. That different rhizobial groups responded
 differently to host size and other ecological factors suggests that
 rhizobia is not an ecologically uniform group, and that entirely neutral
 explanations for our results are unlikely. Host plants may be analogous to
 ‘islands’, where larger plant hosts may accumulate diversity over time,
 through migration opportunities.
description: Summarised data on 16S
 exact genetic variants of rhizobia associated with Acacia acuminata in
 Western AustraliaThis CSV file contains
 data on the presence or absence, and read counts for 16S exact genetic
 variants found associated with individual Acacia trees within 24 sites.
 Also included is metadata for the sites, including all predictors used in
 the associated paper. Please see associated paper for full details on
 sample collection and processing.Dinnage_etal_WA_rhizobia_16S_summarised_data.csvRaw 16S Illumina reads (miseq) of rhizobia collected from soil surrounding Acacia acuminata trees.These sequences come from pooled cultured isolates. Isolates were derived from individual nodules from Acacia acuminata seedling used to trap rhizobia strains from soil that was collected around individual Acacia acuminata trees in the field. This file contains miseq runs for 72 samples, where each sample is the pooled isolates collected from soil surrounding a single Acacia tree. Please see associated paper for full details on sample collection and preparation. The zip file contains two fastq.gz files for each sample, for the forward (R1) and reverse (R2) reads.Dinnage_etal_2018_WA_rhizobia_16s_raw_reads.zip