Can colonization by arbuscular mycorrhizae facilitate co-existence among plant species?
November 24, 2018
Fungi known as arbuscular mycorrhizae form symbiotic relationships with about 73% of all vascular plant species. In this relationship, the mycorrhizae facilitate uptake of nutrients into plant roots in exchange for sugars produced by the plant via photosynthesis. Although mycorrhizal symbiosis has been shown to increase the species diversity of plant communities, individual plant species differ in the extent to which they benefit from the relationship.
Since plants within a community interact and compete with one another for limited resources (soil nutrients, light, water), Stanescu and Maherali (2017) were interested in exploring how arbuscular mycorrhizae may influence this competition and possibly reduce it. In other words, could mycorrhizal symbiosis facilitate coexistence between species that are efficient at taking up resources (strong competitor) with those that are poorer at resource uptake (weak competitor)? This facilitation could spare weak competitors from being excluded from a community via competition and thereby allow for greater species diversity.
For their study, Stanescu and Maherali (2017) used 21 plant species commonly found in old fields of Southern Ontario. Seeds were collected from the Long-Term Mycorrhizal Research Site at the U of G’s Arboretum, a successional old field that was last cultivated in the late 1960s, or purchased if unavailable. Plants were grown in the greenhouse at the University of Guelph’s Phytotron and quantitative measures of competitive ability as well as plant growth when roots were either colonized or uncolonized by mycorrhizae, were obtained.
According to the results of the study, the answer to the above question of whether arbuscular mycorrhizae could facilitate coexistence between species of different competitive abilities is ‘yes’. In the presence of mycorrhizae, growth was generally positive for the 21 species tested while the variance in their competitive abilities was decreased by 73%. Stanescu and Maherali (2017) suggest that the “competitive hierarchy” among the plant species becomes compressed and could be a mechanism by which arbuscular mycorrhizae increase species diversity in plant communities.
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Stanescu S, Maherali H. 2017. Arbuscular mycorrhizal fungi alter the competitive hierarchy among old-field plant species. Oecologia. 183:479-491.