ECOP Subgroup Contributed Talks

Nazanin Zaker

University of Ottawa

"The effect landscape fragmentation on Turing pattern formation"

Many biological populations reside in increasingly fragmented landscapes, which arise from human activities and natural causes. Landscape characteristics may change abruptly in space and create sharp transitions (interfaces) in landscape quality. We study how interactions between individuals and populations in a predator-prey system are affected by habitat fragmentation.We model population dynamics with a predator-prey system in a coupled ecological reaction-diffusion equation in a homogeneous landscape to study Turing patterns that emerge from diffusion driven instability (DDI). We derive the DDI conditions and then we use a finite difference scheme method to numerically explore the general conditions using the May model and we present numerical simulations to illustrate our results. Then we extend our studies on Turing pattern formation by considering a predator-prey system on an infinite patchy periodic landscape. The movement between patches is incorporated into the interface conditions that link the reaction-diffusion system between patches. We use a homogenization technique to obtain an analytically tractable approximate model and determine Turing pattern formation conditions. We use numerical simulation to present our results from this approximation method for this model to explore how differential movement and habitat preference of both species in this model, prey and predator, affect DDI.

Wencel Valega-Mackenzie

University of Tennessee Knoxville

"Resource Allocation in a PDE Ecosystem Model"

The importance of habitat heterogeneity on a diffusing population is crucial to understand population dynamics. In this talk, we formulate a reaction-diffusion population model to study the effect of resource allocation in an ecosystem with resources having their own dynamics in space and time. This approach is more realistic than simply assuming the resource level is not changing as the population changes. Furthermore, we solve an optimal control problem of our ecosystem model to maximize the abundance of a single species while minimizing the cost of inflow resource allocation.

Lucas dos Anjos

National Laboratory for Scientific Computing

"Rapid spread agents may impair biological control in a tritrophic food web with intraguild predation"

The augmentation of natural enemies against agricultural pests is a common tactic undertaken to minimize crop damage without the use of chemical pesticides. Failures of this strategy may result from (i) Allee effects acting on biological control agent; (ii) trophic interactions between the released control agent and native species in the local ecosystem; (iii) excessively rapid spreading agents. To investigate the interplay of these mechanisms in pest biocontrol efficiency in the context of intraguild predation (IGP), we develop a one-dimensional dynamical model of a spatial, tritrophic food web with intraguild predation. We show that the agent's diffusivity (i.e., agent's dispersal speed), and intraguild predator's addition of alternative food sources are important factors in determining the success or failure of pest biocontrol. These results are obtained for spatially explicit models by considering the speed of dispersal of the control agent and the pest. Feedback from theoretical models as the one constructed in this work can provide useful guidelines for practitioners in biological control.

Shadi Sadat Esmaeili-Wellman

University of California Davis

"Noise-Induced vs. Noisy Intrinsic Oscillations in Ecological Systems"

Cyclic and oscillatory behaviors are ubiquitous in ecological systems. These oscillations can be noise-induced or due to intrinsic ecological interactions. Due to the stochastic nature of ecological systems, these types of oscillations appear to be very similar and distinguishing between them using ecological data is a topic of active research. Intrinsic oscillations, unlike noise-induced oscillations, are known to be readily synchronized by local coupling. We propose that spatial patterns in spatially extended systems may contain indirect information about whether cycles are noise-induced or intrinsic. We explore this idea using an ecological model with a period-doubling route to chaos, comparing noise-induced cycles in the stable regime to intrinsic oscillations in the 2-cycle regime, on a lattice with nearest neighbor coupling. Such models implemented on the lattice undergoes a second order phase transition from disordered to synchrony. Our results show that although noise-induced and intrinsic oscillations are effectively indistinguishable in the disordered state, the onset of synchrony allows us to differentiate between these two causes of cycles, across a range of spatial scales of observation.