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Determinism and Stochasticity in Endophytic Fungal Communities

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Intellectual Merit

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  • Community assembly of fungal root endophytes are thought to be driven by deterministic processes.
    • Environment filtering
      • Precipitation- abundance and diversity increase with increases in rainfall.
    • plant host filtering.  Plant identity is found to be the strongest predictor of root endophytic fungal communities. Arbuscular mycorrhiza also form distinct community assemblages in temperate plants.
  • Community ecology is composed of four fundamental processes (selection, speciation, drift, and dispersal). Previous deterministic approaches have focused on elucidating the role of selection but have not addressed the role of drift and dispersal.
  • Stochastic processes such as drift and limited dispersal can alter the community assembly of fungal root endophytes.
    • Dispersal limitations on local scale, thereby causing Priority effects.
      • Ex- Ectomycorrhizal fungi. The timing and order of when ectomycorhizal fungi were inoculated in pines altered the community assembly
      • Priority effects have not been looked in regards to other in endophytic fungi.  
    • Drift
      • Small local species pools- Drift has a more pronounced effect if there are fewer taxa present. Root endophytic studies have been investigated at landscape to global scale and found widespread dispersal, but there is still spatial heterogeneity at a local scale.

Aim 1

Determine the initial colonizers and their respective impact on the resultant fungal communities. 

Methods

  •   Blocked factorial design with plant taxa a greenhouse.
    • 3 plants- Poa pratensis, Poa alpina, achnatherum lettermanii.
  •   Use 1/2” soil core to sample roots at 3 days and 150 days (length of growing season).
  •   Culture and sequence endophytic fungi to determine fungal taxa and abundance. Sequence rhizosphere and bulk soil to determine local species pool.

Aim 2

Determine relative importance of different deterministic and stochastic processes in the field.

Methods

  • Create blocked 3x3x5 factorial of plant taxa x inoculum order x environment with environment as a random effect.
    • 3 plants- Poa pratensis, Poa alpina, achnatherum lettermani
    • 3 inoculum pattern- germinate in sterile environment and inoculate, inoculate in field site, or no inoculation (control). The fungal inoculum will be the most dominant isolate from each of three taxa from the greenhouse experiment.
    • 5 different environmental locations to capture differences in temperature, precipitation, and nutrient availability (N and P).
  •  Plots will be harvested as in Aim 1 but also temperature, precipitation and N and P will be measured at the beginning and end of the experiment.
  • Variance partitioning will be used to determine the relative impact of the environment, priority effects, drift and the plant host on the community assembly. 

Hypotheses

  •   Each plant taxa will initially harbor different initial endophytes due to patch dynamics in the soil.
  •   Fungal endophyte communities from each plant taxa will converge on a similar community composition if plant host selection is the dominant process.
  •   Different fungal initial colonizers yield different community compositions if priority effect matters.
  •   Drift is an important process if the bulk soil fungal communities are hyperdiverse but with few fungal taxa.
  •   Abiotic factors such as precipitation, N, and P will be correlated with fungal diversity and abundance.

Broader impacts

  •   Informative for restoration or agricultural efforts to manipulate the fungal community assembly within plants and aid the success of crops or focal plant species.
  •   Greater understanding of the mechanism underscoring fungal endophytic community assembly would provide more informative parameters for soil and climate change models.

Previous Research Experience

  •   I have successfully cultured and sequenced endophytic fungi from numerous Poa species.
  •   I designed and carried out an experiment studying the interaction between two endophytic fungi- Rhizophagus irregularis and Piriformospora indica within the roots of maize plants in order to test if their mutualistic benefits could occur within the same host.

Cited References

  • Adler, P. B., HilleRisLambers, J., & Levine, J. M. (2007). A niche for neutrality. Ecology Letters, 10(2), 95–104. https://doi.org/10.1111/j.1461-0248.2006.00996.x
  • Bradford, M. A., Davies, C. A., Frey, S. D., Maddox, T. R., Melillo, J. M., Mohan, J. E., … Wallenstein, M. D. (2008). Thermal adaptation of soil microbial respiration to elevated temperature. Ecology Letters, 11(12), 1316–1327. https://doi.org/10.1111/j.1461-0248.2008.01251.x
  • Chesson, P. (2000). General Theory of Competitive Coexistence in Spatially-Varying Environments. Theoretical Population Biology, 58(3), 211–237. https://doi.org/10.1006/tpbi.2000.1486
  • Davison, J., Öpik, M., Daniell, T. J., Moora, M., & Zobel, M. (2011). Arbuscular mycorrhizal fungal communities in plant roots are not random assemblages. FEMS Microbiology Ecology, 78(1), 103–115. https://doi.org/10.1111/j.1574-6941.2011.01103.x
  • Fukami, T. (2015). Historical Contingency in Community Assembly: Integrating Niches, Species Pools, and Priority Effects. Annual Review of Ecology, Evolution, and Systematics, 46(1), 1–23. https://doi.org/10.1146/annurev-ecolsys-110411-160340
  • Gundale, M. J., Wardle, D. A., Kardol, P., Van der Putten, W. H., & Lucas, R. W. (2017). Soil handling methods should be selected based on research questions and goals. New Phytologist, 216(1), 18–23. https://doi.org/10.1111/nph.14659
  • Hawkes, C. V., Kivlin, S. N., Rocca, J. D., Huguet, V., Thomsen, M. A., & Suttle, K. B. (2011). Fungal community responses to precipitation. Global Change Biology, 17(4), 1637–1645. https://doi.org/10.1111/j.1365-2486.2010.02327.x
  • Herrera, J., Khidir, H. H., Eudy, D. M., Porras-Alfaro, A., Natvig, D. O., & Sinsabaugh, R. L. (2010). Shifting fungal endophyte communities colonize Bouteloua gracilis: effect of host tissue and geographical distribution. Mycologia, 102(5), 1012–1026. https://doi.org/10.3852/09-264
  • Kennedy, P. G., Peay, K. G., & Bruns, T. D. (2009). Root tip competition among ectomycorrhizal fungi: Are priority effects a rule or an exception? Ecology, 90(8), 2098–2107. https://doi.org/10.1890/08-1291.1
  • Kivlin, S. N., Lynn, J. S., Kazenel, M. R., Beals, K. K., & Rudgers, J. A. (2017). Biogeography of plant-associated fungal symbionts in mountain ecosystems: A meta-analysis. Diversity and Distributions, 23(9), 1067–1077. https://doi.org/10.1111/ddi.12595
  • Kivlin, S. N., Winston, G. C., Goulden, M. L., & Treseder, K. K. (2014). Environmental filtering affects soil fungal community composition more than dispersal limitation at regional scales. Fungal Ecology, 12(Supplement C), 14–25. https://doi.org/10.1016/j.funeco.2014.04.004
  • Mack, K. M. L., & Rudgers, J. A. (2008). Balancing multiple mutualists: asymmetric interactions among plants, arbuscular mycorrhizal fungi, and fungal endophytes. Oikos, 117(2), 310–320. https://doi.org/10.1111/j.2007.0030-1299.15973.x
  • Peay, K. G., von Sperber, C., Cardarelli, E., Toju, H., Francis, C. A., Chadwick, O. A., & Vitousek, P. M. (2017a). Convergence and contrast in the community structure of Bacteria, Fungi and Archaea along a tropical elevation–climate gradient. FEMS Microbiology Ecology, 93(5). https://doi.org/10.1093/femsec/fix045
  • Peay, K. G., von Sperber, C., Cardarelli, E., Toju, H., Francis, C. A., Chadwick, O. A., & Vitousek, P. M. (2017b). Convergence and contrast in the community structure of Bacteria, Fungi and Archaea along a tropical elevation–climate gradient. FEMS Microbiology Ecology, 93(5). https://doi.org/10.1093/femsec/fix045
  • Ranelli, L. B., Hendricks, W. Q., Lynn, J. S., Kivlin, S. N., & Rudgers, J. A. (2015a). Biotic and abiotic predictors of fungal colonization in grasses of the Colorado Rockies. Diversity and Distributions, 21(8), 962–976. https://doi.org/10.1111/ddi.12310
  • Ranelli, L. B., Hendricks, W. Q., Lynn, J. S., Kivlin, S. N., & Rudgers, J. A. (2015b). Biotic and abiotic predictors of fungal colonization in grasses of the Colorado Rockies. Diversity and Distributions, 21(8), 962–976. https://doi.org/10.1111/ddi.12310
  • Tedersoo, L. (Ed.). (2017). Biogeography of Mycorrhizal Symbiosis (Vol. 230). Cham: Springer International Publishing. https://doi.org/10.1007/978-3-319-56363-3
  • Tedersoo, L., Bahram, M., Põlme, S., Kõljalg, U., Yorou, N. S., Wijesundera, R., … Abarenkov, K. (2014). Global diversity and geography of soil fungi. Science, 346(6213), 1256688. https://doi.org/10.1126/science.1256688
  • Tedersoo, L., Tooming-Klunderud, A., & Anslan, S. (n.d.). PacBio metabarcoding of Fungi and other eukaryotes: errors, biases and perspectives. New Phytologist, n/a-n/a. https://doi.org/10.1111/nph.14776
  • Vellend, M. (2010). Conceptual Synthesis in Community Ecology. The Quarterly Review of Biology, 85(2), 183–206. https://doi.org/10.1086/652373
  • Vellend, M., Srivastava, D. S., Anderson, K. M., Brown, C. D., Jankowski, J. E., Kleynhans, E. J., … Xue, X. (2014). Assessing the relative importance of neutral stochasticity in ecological communities. Oikos, 123(12), 1420–1430. https://doi.org/10.1111/oik.01493
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