Idiosyncrasy and overdominance in the structure of natural communities of arbuscular mycorrhizal fungi: is there a role for stochastic processes?
Article first published online: 24 DEC 2009
© 2009 The Authors. Journal compilation © 2009 British Ecological Society
Journal of Ecology
Volume 98, Issue 2, pages 419–428, March 2010
How to Cite
Dumbrell, A. J., Nelson, M., Helgason, T., Dytham, C. and Fitter, A. H. (2010), Idiosyncrasy and overdominance in the structure of natural communities of arbuscular mycorrhizal fungi: is there a role for stochastic processes?. Journal of Ecology, 98: 419–428. doi: 10.1111/j.1365-2745.2009.01622.x
- Issue published online: 25 JAN 2010
- Article first published online: 24 DEC 2009
- Received 28 July 2009; accepted 16 November 2009 Handling Editor: James Cahill
- microbial diversity;
- niche processes;
- relative species abundances;
- soil biology;
- soil fungi;
- species abundance distributions;
- SSU rDNA
1. Most studies of species abundance patterns focus on conspicuous macroorganisms while microbial communities remain relatively understudied. This bias is a concern given the functional importance and high diversity of microbes.
2. We determine whether a common species abundance distribution (SAD) is observed in communities of a widespread group of soil microbes, the Glomeromycota or arbuscular mycorrhizal (AM) fungi. Using molecular techniques, we intensively sampled the AM fungal community of a woodland–grassland ecotone in Yorkshire, UK. Observed species abundances were compared to theoretical models describing SADs. We also reanalysed 32 previously published data sets in a similar manner.
3. Species abundance distributions in all the AM fungal communities fitted both lognormal and broken-stick models. However, these models consistently and significantly underpredicted the abundance of the most abundant AM fungal taxon. We found that AM fungal communities are typically dominated by a single taxon; representing on average 40% of total abundance within the community. Phylogenetic analysis of the most abundant taxa across data sets showed that the dominant AM fungal type in each community was different and not a widespread generalist.
4. We conclude that a common community structure is present in AM fungal communities from different habitats. The fit to log-normal and broken-stick models suggests the influence of niche differentiation structuring these communities. However, the consistently observed overdominance indicates that local adaptation and stochastic processes may also play important roles in structuring these communities, and we propose a mechanism to explain overdominance in AM fungal communities.
5. Synthesis. This paper applies ecological models derived from studies on larger organisms to microbial communities. Results from this study suggest that a common log-normal SAD is likely to be observed across both microbial and macro taxa. However, due to the distinctive features of microbial biology, some noticeable differences, such as heavy overdominance, may lead to unique structures in microbial communities. This research not only highlights that, to a first approximation, microbial communities follow similar processes and have similar patterns to those of macroorganisms, but also the need for large-scale microbial data sets, if we are to understand the patterns and processes regulating global biodiversity.