Colonization-Competition Tradeoffs as a Mechanism Driving Successional Dynamics in Ectomycorrhizal Fungal Communities

Abstract

Colonization-competition tradeoffs have been shown to be important determinants of succession in plant and animal communities, but their role in ectomycorrhizal (ECM) fungal communities is not well understood. To experimentally examine whether strong spore-based competitors remain dominant on plant root tips as competition shifts to mycelial-based interactions, we investigated the mycelial competitive interactions among three naturally co-occurring ECM species (Rhizopogon occidentalis, R. salebrosus, and Suillus pungens). Each species was grown alone and in all pair-wise combinations on P. muricata seedlings in experimental microcosms and culture assays. Competitive outcomes were assessed from ECM root tip colonization, soil mycelial abundance, and mycelial growth in culture. In the microcosm experiment, we observed a clear competitive hierarchy of R. salebrosus>R. occidentalis>S. pungens. Competitive effects were also apparent in the culture assays, however, no similar hierarchy was present. These results contrast with our previous findings from spore-based competition, suggesting that ECM competitive outcomes can be life-stage dependent. The differing competitive abilities observed here also showed general correspondence with patterns of ECM succession in Pinus muricata forests, indicating that competitive interactions may significantly influence temporal patterns of ECM community structure.

Ectomycorrhizal host specificity in a changing world: can legacy effects explain anomalous current associations?

“…We have also shown that S. subaureus can colonize two Pinaceae host species, suggesting that this species is a host generalist rather than a Quercus specialist. Because the capacity to colonize alternative hosts can be controlled either at the point of spore germination or during downstream signaling processes, host identity may influence colonization differently depending on whether spores must be germinated in order to establish fungal presence, or whether extant mycorrhizas are already present on neighboring plants (Molina et al ., ; Kennedy et al ., ). Consistent with earlier studies (i.e.…”

“…Spores from the nine S. subaureus sporocarps were collected following the methods outlined by Kennedy et al . () and stored in moistened sterile growth media at 4 ° C until use. Plant growth medium consisting of a 2 : 2 : 1 mix of peat (no.…”

Predation resistance does not trade off with competitive ability in early-colonizing mosquitoes

“…Species that are less rapid colonizers, on the other hand, should be better resource competitors, which ultimately enables them to colonize, and eventually to dominate, habitats in which early colonizers are already abundant (Tilman 1994, Connell and Slatyer 1977). This tradeoff has been demonstrated in laboratory experiments with protozoans (Cadotte et al 2006) and fungi (Kennedy et al 2011), and in a field study with terrestrial plants (Gleeson and Tilman 1994). …”

How Ectomycorrhizae Structures Boost the Root System?

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