Evolution of behaviour and life history decisions by theoretical modelling

Evolution of the vertebrate stress response

All organisms have a stress response system to cope with environmental threats, yet its precise form varies hugely within and across individuals, populations and species. While the physiological mechanisms are increasingly understood, how stress responses have evolved remains elusive. In a first step, starting with a simple model containing small mechanistic detail, we could show that important insights can be gained from models that incorporate physiological mechanisms within an evolutionary optimality analysis. Our approach revealed that environmental predictability and physiological constraints are key factors shaping stress response evolution, generating testable predictions about variation across species and contexts. In this ongoing research focus, we will develop and analyse models, which include more mechanistic aspects of the highly complex vertebrate stress system, as well as target ontogenetic effects on the stress response system.    

Investigators: This research focus is pursued by an international research network initiated by Barbara Taborsky. Additional network members are Sinead English, University of Bristol, UK; Tim W. Fawcett, University of Exeter, Exeter Campus, UK; Bram Kuijper, University of Exeter, Penryn and Exeter Campus, UK; Olof Leimar, Stockholm University, Sweden; John M. McNamara, School of Mathematics, University of Bristol, UK; Suvi Ruuskanen, University of Turku, Finland; Carmen Sandi, Ecole Polytechnique Federale de Lausanne (EPFL), SwitzerlandTaborsky, B., English, S., Fawcett, T.W., Kuijper, B., Leimar, O., McNamara, J.M., Ruuskanen, S. & Sandi, C. (2021). Towards an evolutionary theory of stress responses. Trends. Ecol. Evol., 36, 39-48

Sample publication

Taborsky, B., English, S., Fawcett, T.W., Kuijper, B., Leimar, O., McNamara, J.M., Ruuskanen, S. & Sandi, C. (2021). Towards an evolutionary theory of stress responses. Trends. Ecol. Evol., 36, 39-48

All organisms have fast reacting stress responses sharing a typical shape, even if they occur on slightly different time scales (a). They start out from a baseline, rise quickly to a peak concentration of a stress-induced molecule, and then fall back usually slowly to the baseline. (b) First model results showing the dependence of peak concentration and stress response time course in dependence of risk level and environmental autocorrelation in an environment where rapid predator attacks act as major stressor. The autocorrelation parameter determines how predictable these attacks are. (Figures adapted from Taborsky et al. 2021, Trends Ecol. Evol.)

Life history models: size-dependent and size-independent mortality give rise to diversifying evolution

In the last decade examples have accumulated of phenotypic plasticity acting during different ontogenetic stages. Nevertheless a theoretical framework has been lacking to predict (a) how the plasticity of fundamental life-history trade-offs depend on energetic availability and (b) how the plasticity of trade-offs should change throughout life. By evolutionary modelling we investigated how (a) the plasticity of trade-offs between reproduction, survival and self-maintenance strategies in dependence of energetic constraints. Further we unravelled how this plasticity changes with age: in most environments, the optimal degree of plasticity varies with age in a non-monotonic fashion: plasticity is low at the beginning and the end of life, whereas the highest values occur at intermediate ages.

Principal investigator: Barbara Taborsky

Sample publications

Taborsky, B., Heino, M. & Dieckmann, U. (2018): Life history multistability caused by size-dependent mortality. Amer. Nat. 192, 62-71

Fischer, B., van Doorn, G. S., Dieckmann, U. & Taborsky, B. (2014): The evolution of age-dependent plasticity. American Naturalist, 183, 108-125.

Taborsky, B., Dieckmann, U, & Heino, M. (2012): Size-dependent mortality and competition interactively shape community diversity. Evolution 66, 3534-3544.

Fischer, B., Taborsky, B. & Kokko, H. (2011): How to balance the offspring quality-quantity trade-off when environmental cues are unreliable. Oikos 120, 258-270.

Fischer, B., Dieckmann, U. & Taborsky, B. (2011): When to store energy in a stochastic environment. Evolution 65, 1221-1232.

Fischer, B., Taborsky, B. & Dieckmann, U. (2009): Unexpected patterns of energy allocation in stochastic environments. American Naturalist 173, E108-120.

Taborsky, B., Dieckmann, U, & Heino, M. (2003): Unexpected discontinuities in life-history evolution under size-dependent mortality. Proceedings of the Royal Society B, 270, 713-721.

The joint effects of size-dependent and size-independent mortality in nature gives rise to the evolution of divergent ecotypes differing in their life-history