Serpentine and non-serpentine ecotypes of Collinsia sparsiflora associate with distinct arbuscular mycorrhizal fungal assemblages

Our plain-English summary of Serpentine and non-serpentine ecotypes of Collinsia sparsiflora associate with distinct arbuscular mycorrhizal fungal assemblages, by S.P. Schechter, T.D. Bruns (Molecular Ecology, 2008).

The study

• Authors: S.P. Schechter, T.D. Bruns
• Journal: Molecular Ecology
• Published: 2008;17(13):3198-210
• Cited by: 60 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Although plant adaptation to serpentine soils has been studied for several decades, the mechanisms of plant adaptation to edaphic extremes are still poorly understood. Arbuscular mycorrhizal fungi (AMF) are common root symbionts that can increase the plant hosts' establishment and growth in stressful environments. However, little is known about the role plant-AMF interactions play in plant adaptation to serpentine. As a first step towards understanding this role, we examined the AMF assemblages associated with field populations of serpentine and non-serpentine ecotypes of California native plant Collinsia sparsiflora. We sampled roots of C. sparsiflora from three serpentine and three non-serpentine sites in close proximity (110 m to 1.94 km between sites) and analysed the small subunit ribosomal DNA gene amplified from root DNA extracts using AMF-specific primers. A total of 1952 clones from 24 root samples (four from each site) were sequenced. We used sequence similarity and phylogenetic analysis to determine operational taxonomic units (OTU) resulting in 19 OTUs representing taxa from six AMF genera, including one serpentine-specific OTU. We used Bray-Curtis similarity, multidimensional scaling and analysis of similarity to compare root sample AMF assemblages. These analyses clearly showed that plant ecotypes associated with distinct AMF assemblages; an Acaulospora OTU-dominated serpentine, and a Glomus OTU-dominated non-serpentine assemblages. Species diversity and evenness were significantly higher in serpentine assemblages. Finally, relate analysis showed a relationship between ecotype AMF assemblages and soil nutrients. This study reveals a strong relationship between AMF associates and plant adaptation to edaphic extremes.

In plain English

This study is about plants and soil fungi. It does not mention asbestos, fibers or human health. The authors studied a small California wildflower, Collinsia sparsiflora, at a northern California reserve where earlier work had identified populations adapted to serpentine soil and populations adapted to non-serpentine soil. In March 2005 they sampled plants from four patches at each of six sites and used root DNA to identify arbuscular mycorrhizal fungi, which live inside plant roots. One serpentine site gave too few fungal sequences and was left out of the main comparison. The authors found 19 fungal types from six genera. Fungal groups on serpentine-adapted plants differed significantly from those on non-serpentine plants. Serpentine plants had similar numbers of Acaulospora and Glomus sequences, while non-serpentine plants were dominated by Glomus. One type, Glomus 6, was found only on serpentine plants. Fungal diversity and evenness were higher on serpentine plants, but the number of fungal types did not differ significantly. Fungal patterns were related to soil nutrients. The authors concluded that this indicates a strong relationship between these fungi and plant adaptation to serpentine. They noted that soil, the plant, or both could be responsible.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Field sampling study using DNA (molecular) identification of root fungi, comparing plant populations adapted to serpentine and to non-serpentine soils
• Who was studied: Collinsia sparsiflora plants (a California native annual) from six populations at the McLaughlin Reserve in Napa, Lake and Yolo counties, northern California, sampled in March 2005. There were three serpentine sites (S1, S2, S3) and three non-serpentine sites (NS1, NS2, NS3), with 24 root samples in total, each representing 10–26 plants. Site S3 was excluded from the assemblage analysis.
• Exposure: Growth on serpentine soil versus non-serpentine soil (derived from volcanic or valley sediment materials). The sites were distinguished by soil calcium to magnesium ratio. No asbestos or fiber exposure was studied.
• Main results:
  • All six plant populations were heavily colonized by the fungi (44–57% of root length), with no significant difference between samples
  • Of 1952 clones sequenced, 64% were fungal (AMF) sequences. Site S3 produced only 15 AMF sequences and was excluded from the assemblage analysis.
  • 19 fungal types (OTUs) from six genera were identified. Glomus made up 72% of sequences and Acaulospora 25%. One type, Glomus 6, was found only in serpentine ecotypes.
  • Fungal assemblages differed overall (global ANOSIM R = 0.49, P < 0.001). The serpentine sites S1 and S2 did not differ from each other, but both differed significantly from the three non-serpentine sites.
  • Serpentine ecotype samples averaged 133 Acaulospora and 102 Glomus clones per site. Non-serpentine samples averaged 233 Glomus and 16 Acaulospora clones per site.
  • Two types, Glomus 1 and Acaulospora 1, together accounted for 47% of the difference between serpentine and non-serpentine assemblages (28% and 19% respectively)
  • Serpentine ecotype assemblages had significantly higher diversity (H′ = 1.17 versus 0.68) and evenness (J′ = 0.68 versus 0.45) than non-serpentine assemblages. Species richness did not differ significantly (P = 0.29).
  • Fungal assemblage patterns were significantly related to soil nutrient patterns (RELATE Rho = 0.507, P < 0.001)
  • No trend of decreasing similarity with distance between sites was found
• The authors' conclusion: The authors concluded that the distinct fungal assemblages indicate a strong relationship between these fungi and plant adaptation to serpentine. They stated that soil factors, host factors, or both could be responsible for the difference.
• Limitations the authors state:
  • Clone counts were used as a stand-in for actual fungal abundance, which the authors say should be done with caution
  • The primer used is known to exclude one fungal family (Paraglomeraceae)
  • The number of patches sampled was limited to reduce harm to the plant populations
  • One serpentine site (S3) was excluded from the assemblage analysis because of too few sequences
  • It is difficult to separate the effects of soil from host-plant or plant-community influences on the fungal assemblages

Topics

The National Library of Medicine indexes this study under subjects our site covers: Chrysotile.

Medical terms in this study, explained in our Lexicon: Serpentine Group.

Related studies

• Serpentine soils do not limit mycorrhizal fungal diversity — S. Branco, R.H. Ree (2010)
• Serpentine soils promote ectomycorrhizal fungal diversity — S. Branco (2010)
• Collinsia sparsiflora in serpentine and nonserpentine habitats: using F2 hybrids to detect the potential role of selection in ecotypic differentiation — J.W. Wright, M.L. Stanton (2007)
• Influence of the Ca/Mg ratio on Cu resistance in three Silene armeria ecotypes adapted to calcareous soil or to different, Ni- or Cu-enriched, serpentine sites — A. Lombini, M. Llugany, et al. (2003)
• Fungal diversity is not determined by mineral and chemical differences in serpentine substrates — S. Daghino, C. Murat, et al. (2012)
• Population resequencing reveals local adaptation of Arabidopsis lyrata to serpentine soils — T.L. Turner, E.C. Bourne, et al. (2010)

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