My PhD research career began in my home city where I studied the mutualism between legumes and bacterial symbionts at University of Toronto. I found the biological system utterly captivating, and this ultimately drew me to Australia with its iconic and highly diverse Acacia legumes. In Australia, I took up a postdoc position at CSIRO studying the diversity of Acacia associated bacterial symbionts in South west Australia. This eventually led me to Canberra, where I am now a DECRA fellow in the Borevitz group continuing my expanding research passions in plant host microbiomes and soil microbe ecology.
Current research interests
I study nitrogen-fixing symbionts that associate with legume roots (a.k.a. rhizobia). Although microscopic, rhizobia play a major role in global nitrogen-cycles because both they and their plant hosts are so globally widespread. Rhizobia spend much of their time as free-living colonies in the soil so the goal of my DECRA is to understand how selective pressures from the soil environment impact how these symbiont associates with their hosts. For example, do more stressful soil environments lead to a stronger mutualistic relationship, or can it lead to a mutualism break down? How does the soil environment impact the dynamics of horizontally transferred genes, including genes that control symbiosis? I will be exploring these and other questions, moving towards the broader goal of understanding how we can leverage these mutualistic relationships for various applications, such as regenerative agriculture and habitat restoration in a changing climate.
Challenges in my field
Rhizobia, like all soil bacteria lead elusive lives in their natural and microscopic habitat. Because we cannot directly observe them, we have to use various indirect approaches, such as next generation sequencing, to gain a basic understanding of their ecology in the soil. The consequence of this approach is that, for each soil sample, we must shred the DNA of all organism into a fragmented, disorganized mess. Since a small soil sample can contain thousands to millions of species, a large part of my research will be implementing new bioinformatic approaches that enable us to infer the ecological and evolutionary dynamics of specific taxa, such as rhizobia. Overcoming these challenges will enable insight into how we can manipulate the soil microbe community and plant-microbe associations in complex soil environments.
1. Simonsen, A.K., Barrett, L.G., Thrall, P.H., & Prober, S.M. (2019). Novel model-based clustering reveals ecologically differentiated bacterial genomes across a large climate gradient. Ecology Letters (in press).
2. Dinnage, R.*, Simonsen, A. K.*, Barrett, L. G., Cardillo, M., Raisbeck‐Brown, N., Thrall, P. H., & Prober, S. M. (2019). Larger plants promote a greater diversity of symbiotic nitrogen‐fixing soil bacteria associated with an Australian endemic legume. Journal of Ecology, 107(2), 977-991.
(* indicates shared first author)
3. Harrison, T. L.*, Simonsen, A. K., Stinchcombe, J. R., & Frederickson, M. E. (2018). More partners, more ranges: generalist legumes spread more easily around the globe. Biology letters, 14(11), 20180616.
4. Simonsen, A.K., Dinnage, R., Barrett, L.G., Prober, SM & Thrall, P.H. (2017). Symbiosis limits establishment of legumes outside their native range at a global scale. Nature Communications, 8, 14790.
5. Duncan, E.G., O’Sullivan, C.A., Simonsen, A.K., Roper, M.M., Peoples, M.B., Treble, K. & Whisson, K. (2017) The nitrification inhibitor 3,4,-dimethylpyrazole phosphate strongly inhibits nitrification in coarse-grained soils containing a low abundance of nitrifying microbiota. Soil Research, 55, 28–37.
6. Duncan, E.G., O’Sullivan, C.A., Simonsen, A.K., Roper, M.M., Treble, K. & Whisson, K. (2016) A composite guanyl thiourea (GTU), dicyandiamide (DCD) inhibitor improves the efficacy of nitrification inhibition in soil. Chemosphere, 163, 1–5.
7. Seabloom, E.W., Borer, E.T., Buckley, Y.M., Cleland, E.E., Davies, K.F., Firn, J., Harpole, W.S., Hautier, Y., Lind, E.M., MacDougall, A.S., Orrock, J.L., Prober, S.M., Adler, P.B., Anderson, T.M., Bakker, J.D., Biederman, L.A., Blumenthal, D.M., Brown, C.S., Brudvig, L.A., Cadotte, M., Chu, C., Cottingham, K.L., Crawley, M.J., Damschen, E.I., Dantonio, C.M., DeCrappeo, N.M., Du, G., Fay, P.A., Frater, P., Gruner, D.S., Hagenah, N., Hector, A., Hillebrand, H., Hofmockel, K.S., Humphries, H.C., Jin, V.L., Kay, A., Kirkman, K.P., Klein, J.A., Knops, J.M.H., La Pierre, K.J., Ladwig, L., Lambrinos, J.G., Li, Q., Li, W., Marushia, R., McCulley, R.L., Melbourne, B.A., Mitchell, C.E., Moore, J.L., Morgan, J., Mortensen, B., O’Halloran, L.R., Pyke, D.A., Risch, A.C., Sankaran, M., Schuetz, M., Simonsen, A.K., Smith, M.D., Stevens, C.J., Sullivan, L., Wolkovich, E., Wragg, P.D., Wright, J. & Yang, L. (2015) Plant species’ origin predicts dominance and response to nutrient enrichment and herbivores in global grasslands. Nature Communications, 6, 7710.
8. Simonsen, A.K., Han, S., Rekret, P., Rentschler, C.S., Heath, K.D. & Stinchcombe, J.R. (2015) Short-term fertilizer application alters phenotypic traits of symbiotic nitrogen fixing bacteria. PeerJ, 3, e1291.
9. Simonsen, A.K., Chow, T. & Stinchcombe, J.R. (2014) Reduced plant competition among kin can be explained by Jensen’s inequality. Ecology and Evolution, 4, 4454–4466.
10. Simonsen, A.K. & Stinchcombe, J.R. (2014) Standing genetic variation in host preference for mutualist microbial symbionts. Proceedings. Biological Sciences / The Royal Society, 281.
11. Simonsen, A.K. & Stinchcombe, J.R. (2014) Herbivory eliminates fitness costs of mutualism exploiters. The New Phytologist, 202, 651–661.
12. Stinchcombe, J.R., Simonsen, A.K. & Blows, M.W. (2014) Estimating uncertainty in multivariate responses to selection. Evolution, 68, 1188–1196.
13. Seabloom, E.W., Borer, E.T., Buckley, Y., Cleland, E.E., Davies, K., Firn, J., Harpole, W.S., Hautier, Y., Lind, E., MacDougall, A., Orrock, J.L., Prober, S.M., Adler, P., Alberti, J., Anderson, T.M., Bakker, J.D., Biederman, L.A., Blumenthal, D., Brown, C.S., Brudvig, L.A., Caldeira, M., Chu, C., Crawley, M.J., Daleo, P., Damschen, E.I., D’Antonio, C.M., DeCrappeo, N.M., Dickman, C.R., Du, G., Fay, P.A., Frater, P., Gruner, D.S., Hagenah, N., Hector, A., Helm, A., Hillebrand, H., Hofmockel, K.S., Humphries, H.C., Iribarne, O., Jin, V.L., Kay, A., Kirkman, K.P., Klein, J.A., Knops, J.M.H., La Pierre, K.J., Ladwig, L.M., Lambrinos, J.G., Leakey, A.D.B., Li, Q., Li, W., McCulley, R., Melbourne, B., Mitchell, C.E., Moore, J.L., Morgan, J., Mortensen, B., O’Halloran, L.R., Pärtel, M., Pascual, J., Pyke, D.A., Risch, A.C., Salguero-Gómez, R., Sankaran, M., Schuetz, M., Simonsen, A.K., Smith, M., Stevens, C., Sullivan, L., Wardle, G.M., Wolkovich, E.M., Wragg, P.D., Wright, J. & Yang, L. (2013) Predicting invasion in grassland ecosystems: is exotic dominance the real embarrassment of richness? Global Change Biology, 19, 3677–3687.
14. Campitelli, B.E. & Simonsen, A.K. (2012) Plant evolutionary ecology: molecular genetics, global warming and invasions, and the novel approaches we are using to study adaptations. The New Phytologist, 196, 975–977.
15. Simonsen, A.K. & Stinchcombe, J.R. (2010) Quantifying Evolutionary Genetic Constraints in the Ivyleaf Morning Glory, Ipomoea hederacea. International Journal of Plant Sciences, 171, 972–986.
16. Campitelli, B.E., Simonsen, A.K., Wolf, A.R., Manson, J.S. & Stinchcombe, J.R. (2008) Leaf shape variation and herbivore consumption and performance: a case study with Ipomoea hederacea and three generalists. Arthropod-Plant Interactions, 2, 9–19.
17. Simonsen, A.K. & Stinchcombe, J.R. (2007) Induced responses in Ipomoea hederacea: simulated mammalian herbivory induces resistance and susceptibility to insect herbivores. Arthropod-Plant Interactions, 1, 129–136.