MS06 - ECOP-1
Student-Alumni Council Room (#2154) in The Ohio Union

Microbial and ecological dynamics across the many natural scales

Thursday, July 20 at 10:30am

SMB2023 SMB2023 Follow Thursday during the "MS06" time block.
Room assignment: Student-Alumni Council Room (#2154) in The Ohio Union.
Note: this minisymposia has multiple sessions. The other session is MS07-ECOP-1 (click here).

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Christopher Heggerud, Tyler Meadows


Biological interactions occur in a myriad of different temporal, spatial, and ecological scales. Explicit consideration of such multiscale dynamics has led to a much deeper understanding of ecological phenomena and has left even more unanswered questions. In this session we wish to explore the scientific advances that have taken place in modeling biological dynamics that occur on the various natural scales. In particular we highlight transient dynamics that occur on biologically relevant timescales, trophic interactions among species of various size scales, and community dynamics that can occur on various spatial scales. The goal of this session is to highlight the many different scales involved in biological dynamics, discuss the useful mathematical tools for studying such systems and to show comparison by giving examples within both ecological and microbial systems.

Alan Hastings

University of California - Davis (Environmental Science and Policy)
"Transient dynamics: the key to ecological understanding"
Much of classical ecological theory is focused on the long -term behavior of ecological models yet the time scales of ecological dynamics are such that a focus on asymptotic behavior is likely misguided. Ecological conclusions change in important ways when focusing on appropriate time scales. I will begin with some of my much older work that suggests the importance of transients and some of the challenges. I will then focus on more recent work, most of which has been done with a wonderful group of colleagues from a working group that began at NIMBioS. We have given a rough classification of features that produce transients similar to approaches for understanding dynamical systems, examined implications for management, and examined transients in systems where stochasticity is important. I will also consider related issues that arise when taking into consideration changing external conditions (global change) and the implications for ecological prediction.

Rebecca Tyson

University of British Columbia, Okanogan
"Mutualism at the leading edge: Insights into the eco-evolutionary dynamics of host-symbiont communities during range expansion"
The evolution of mutualism between hosts and symbiont communities plays and essential role in maintaining ecosystem function and thus should have a profound effect during range expansion. In particular, the presence of mutualistic symbionts at the leading edge should enhance the propagation of the host and the overall symbiont community. Here we develop a theoretical framework that captures the eco-evolutionary dynamics of resource exchange between host symbionts and their dispersal in space. We provide quantitative insights into how the evolution of resource exchange may shape community strucure during range expasion. Parasitic symbionts receive the same amount of resources from the host as mutualistic symbionts, but at lower cost. This selective advantage is strengthened with resource availability (i.e., with host density), promoting mutualism at the range edges, where host density is low, and parasitism in the core of the range, where host desnity is higher. Host growth depends on the overall benefit provided by the symbiotic community, and is maximal at the expansion edges, where symbionts are more mutualistic. The expansion of host-symbiont communities is pulled by the hosts, but pushed by the symbionts. The spatial selection also influences the speed of spread. In particular, hosts with low dependence on their symbionts, or host-symbiont communities with high symbiont density at their core (e.g., resulting from more mutualistic hosts) or at their leading edge (e.g., resulting from symbiont inoculation) enhance the speed of spread into new territories.
Additional authors: Maria M. Martignoni, Rebecca C. Tyson, Oren Kolodny, Jimmy Garnier

Susmita Sadhu

Georgia College & State University (Department of Mathematics)
"Methods for analyzing long transient dynamics in a three-dimensional predator-prey model featuring two timescales"
The leading role of long transient dynamics in ecological timescales can be very important in explaining regime shifts. However, analytical techniques for studying long transients in relevant timescales in three or higher-dimensional ecological models is still at its infancy. In this talk, I will consider a three-dimensional predator-prey model featuring two-timescales that studies the interaction between two species of predators competing for their common prey with explicit interference competition. I will consider two different scenarios in a parameter regime near {emph{singular Hopf bifurcation}} of the coexistence equilibrium point. In one case, the system exhibits bistability between a periodic attractor and a boundary equilibrium state, with long transients characterized by rapid small-amplitude oscillations and slow variation in amplitudes, while in the other, the system exhibits chaotic {emph{mixed-mode oscillations}}, featuring concatenation of small and large-amplitude oscillations, as long transients before approaching a stable limit cycle. To analyze the transients, the system is reduced to a suitable normal form near the singular Hopf point. Exploiting the separation of timescales and the underlying geometry of the normal form, the transient dynamics are analyzed. The analyses are then used to devise methods for identifying early warning signals of a large population transition leading to an outbreak or resulting in an extinction of one of the species.
Additional authors: Dr. S. C. Thakur, Auburn University

Tyler Meadows

Queen's University (Mathematics and Statistics)
"Evolution of persister cells"
Most β-lactam antibiotics, such as penicillin, function by disrupting membrane formation during mitosis. So-called persister cells survive antibiotic treatment by entering a semi-dormant state. These cells can be used to found a new culture of microorganisms that is equally susceptible to the antibiotics as the original culture. We investigate a model for the competition between two species of bacteria with different affinities for the persister type on both the population scale and the evolutionary scale.
Additional authors: Troy Day Queen's University Mathematics and Statistics, Chongming Li Queen's University Mathematics and Statistics

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