Competitive interactions among three ectomycorrhizal fungi and their relation to host plant performance

Abstract

Summary 1.Competition strongly influences many species assemblages, but its role in mycorrhizal fungal interactions is not well understood. We examined interactions among three ectomycorrhizal (ECM) species to determine if the structure of competition could be characterized by either competitive networks (where no clear hierarchy exists in the outcome of competition between various species pairs) or competitive hierarchies (where one species out competes all other species). Using a bioassay experiment, we inoculated Pinus muricata seedlings with threeRhizopogon species ( R. occidentalis , R. salebrosus , and R. vulgaris ) in single-, two-, and three-species treatments. After 7 months, we assessed the relative abundance of each species in each treatment using real-time PCR of internal transcribed spacer rDNA. 3. We found that R. occidentalis was strongly inhibited by R. vulgaris and R. salebrosus in all competition treatments. In contrast, R. vulgaris and R. salebrosus had similar ECM biomasses in the two-species treatment, but R. vulgaris had significantly higher biomass than R. salebrosus in the three-species treatment. 4. In the single-species treatments, seedlings colonized by the competitive dominants had higher shoot biomass and total leaf nitrogen, but also higher percentage ECM biomass. In the multi-species treatments, seedlings had either equivalent or somewhat lower shoot biomass and total leaf nitrogen than their respective single-species treatments. 5. Synthesis. Our results indicate that ECM competition does not appear to be characterized by strict networks or hierarchies. Instead, the outcome is dependent on the conditions of the local environment in which it occurs. There also does not seem to be a clear relationship between ECM competitive ability and plant performance, but competition does appear to negatively affect the ability of ECM fungi to provide benefits to their hosts.

Trade-offs between arbuscular mycorrhizal fungal competitive ability and host growth promotion in Plantago lanceolata

“…In most of these systems the better competitor provided the greatest mutualistic beneWt (e.g., Miller 2007;Yu and Pierce 1998). In another microbial system, among three ectomycorrhizal fungal species, the better fungal competitors may have also been the better symbionts, although host beneWt varied between competitive and non-competitive settings (Kennedy et al 2007).…”

Ecological and functional roles of mycorrhizas in semi-arid ecosystems of Southeast Spain

“…Research concerning the impact of mycorrhizal fungi on plant community composition and functioning concludes that the diversity and activity of mycorrhizal fungi is a key mechanism for ecosystem functioning Hart and Klironomos, 2002;Kennedy et al, 2007;Martínez-García and Pugnaire, 2009;Read, 1998). Conversely, diversity and structure of plant cover affects diversity of AM fungal populations (Bever et al, 2002;Read, 2002;Wolfe et al, 2005).…”

“…The nature of the community feedbacks in mycorrhizal associations has been investigated with special emphasis on the several mechanisms/factors responsible for the ecological interactions involved. These mechanisms/factors include: (i) the functional specificity of the different plant-fungus combinations (Klironomos, 2002;van der Heijden et al, 1998); (ii) the mycorrhizal dependency of the plant species involved (Hart and Klironomos, 2002;Kennedy et al, 2007;Read, 1998); and (iii) the structure of the individual plant species within the community (O'Connor et al, 2002;van der Heijden, 2002;van der Heijden et al, 2006).…”

Effects of living crown reduction on needle element status of Scots pine

“…However, the differences in genetic properties of the trees and the species composition and diversity of the ectomycorrhizal associations may affect the foliar nutrition (Knight 1978, Schmidtling 1995, Baxter and Dighton 2001, Xu et al 2003, Kennedy et al 2007, Korkama-Rajala et al 2008). The selection mechanisms employed by Gremmeniella abietina in achieving successful infection of the trees are also variable, and the original foliar nutrient status of the unaffected control trees may have also been partly altered, especially in (I), over the years.…”