Examining the role of competition in ectomycorrhizal interactions Competition: Research questions Study System Mycorrhizal abundances at Pt. Reyes
Hayes, Patty, Copy Editor has reference to this Academic Journal, PHwiki organized this Journal Examining the role of competition in ectomycorrhizal interactions Peter Kennedy NPER post-doctoral fellow – UC Berkeley firstname.lastname@example.org Competition: Typically highly asymmetric. Competitive hierarchies are common. Order of arrival can significantly effect outcome. A major factor structuring natural assemblages Generalizations Research questions 1. How is ECM competition structured in the field What are main mechanisms by which it occurs 2. Are there competitive hierarchies among ECM fungi If so, are competitive dominants also better symbionts
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Study System Point Reyes National Seashore, CA Bishop Pine (Pinus muricata) Rhizopogon spp. Mycorrhizal abundances at Pt. Reyes Forest type Young Mature Rhizopogon occidentalis Rhizopogon vulgaris Rhizopogon salebrosus Rhizopogon evadens (0-10 yr) (40-60 yr) ECM Species Rhizopogon is a dominant colonizer of seedlings in post-fire in addition to primary successional settings. Lab Study Results Timing of colonization differed considerably between species Strong asymmetry in addition to priority effects were observed Inoculation curves very similar between species Kennedy in addition to Bruns (2005), New Phyt. 166: 631-638.
Field competition experiment Two species: R. salebrosus (RS) in addition to R. occidentalis (RO) Treatments: no inoculum, single species, two species 20 replicates/treatment at three sites Harvested seedlings after 5 in addition to 10 months Analyzed ECM root tips with real-time PCR Results: Fungi Highly asymmetric (i.e. mostly all or nothing) Priority effect again observed lab in addition to field results = good correspondence What about the few co-colonized seedlings R. salebrosus is not always the competitive inferior! a a
Results: Plants Being mycorrhizal is very important in terms of growth, but ECM competition has little effect What about the natural pattern Types of ECM Competition Exploitation Interference Time
Competitive hierarchy experiment R. salebrosus Competitive intransivity Four species: Rhizopogon vulgaris (RV), R. salebrosus (RS), R. evadens (RE), R. occidentalis (RO) All pair-wise in addition to one three-way combination (RO/RV/RS) Spores of competitors added at the same time (106 spores/species) 10 replicates/treatment grown as long as 8 months (growth chamber) Harvested all seedlings in addition to root tips analyzed with real-time PCR Results: A Competitive Hierarchy! What about the plants Seedling biomass Shoot Nitrogen a a b b The best competitors may be the best symbionts
Applications as long as Forestry Mixed species ECM inoculations may not be effective – competitive interactions are strong in addition to highly asymmetical. Differences in timing of spore germination may affect seedling ECM composition – priority effects observed in both lab in addition to field studies. More studies are necessary to determine competitive ability – as long as Rhizopogon, competitive dominants appear to be the best symbionts. Acknowledgements Sarah Bergemann, Sara Hortal, Tom Bruns Bruns lab members, UC Berkeley Point Reyes National Seashore National Parks Ecological Research Fellowship National Science Foundation Ongoing experiments Do spore- vs. mycelial-based ECM competition have different outcomes Can priority effects be reversed by altering the timing of colonization Does ECM competition occur mainly through direct or indirect interactions Does spore density in addition to soil heating affect the outcome of ECM competition
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