BioMaths Colloquium Series – 2022/23
7 June 2023 – 3pm
Join us at 2:45 for coffee tea and biscuits in Wallace 218
(Wallace Building – Singleton Campus)
or Zoom (register here)
How does negative plant-soil feedback across life stages affect the Janzen-Connell hypothesis?
Annalisa Iuorio is a postdoctoral researcher at the University of Vienna supported by an FWF Hertha Firnberg Fellowship focused on mathematical models for vegetation dynamics involving autotoxicity. Her research expertise lies in the construction and analysis of reaction-diffusion-ODE systems arising in different areas of applications in collaboration with experts from the applied fields; in particular, she works together with theoretical ecologists with the aim to provide a rigorous foundation to biological evidence emerged through experimental observations and construct novel tools to better understand the dynamics behing several types of vegetation patterns.
A widely accepted explanation for the maintenance of tree species biodiversity in tropical (rain)forests is the Janzen-Connell hypothesis, which states that growth of seedlings is suppressed in the proximity of conspecific adult trees due to negative plant-soil feedback. Several studies justify such feedback with the presence of soil-borne pathogens. However, negative plant-soil feedback may involve additional mechanisms, including autotoxicity. The identification of the main mechanisms behind the emergence of such transient structures from field observations remains a challenging open problem, due to the strong intertwinement of the above factors in natural circumstances. An essential task therefore consists in constructing mathematical models incorporating both effects showing the ability to support the emergence of (transient) JC distributions: this can then be used as a crucial tool to perform analytical investigations with the goal to assess the impact of both factors on such structures.
To this aim, we develop and analyse a novel reaction-diffusion-ODE model, describing the interactions within tropical tree species across different life stages (seeds, seedlings, and adults) as driven by negative plant-soil feedback. The model is parameterised to represent realistic tropical tree dynamics. In particular, we show the existence of travelling wave solutions which verify the Janzen-Connell hypothesis in the case of strong toxicity. Moreover, we test the hypothesis that the travelling profiles observed numerically for a vast parameter range indeed correspond to pulled fronts, and calculate their linear spreading speed.
The modelling framework established here provides a valuable tool to advance our understanding of the Janzen-Connell hypothesis and can be used to test future theoretical investigations aimed to disentagle the effect of relevant ecological mechanisms in the emergence of this important transient pattern. Additionally, the methodology illustrated here to analyse travelling waves in a system of four reaction-diffusion-ODEs represents a further step in our understanding of this type of problems and can serve as inspiration for analogous models arising in several applications.