Temporal constraints on reproduction and growth in a seasonal environment

Abstract

The variety of life forms is one of the most striking phenomena that have stimulated research in evolutionary biology and ecology over recent decades. The crucial role in defining the most characteristic features of living organisms is dedicated to so-called life history traits (Stearns 1992, Roff 2002). Biological species are characterized by several life history traits such as lifespan, rate of ageing, sexual size dimorphism, but also traits investigated in this work: body size, growth rate, mode of reproduction, and timing and synchrony of breeding. Those traits define functional features of species with consequences going far beyond simple classification. From individual to the ecosystem level, life history traits affect physiology, behaviour but also interactions between species (Davies et al. 2012). Hence, the knowledge about how life history traits evolve is central for understanding important scientific questions but also practical ecological or conservation issues (Allen 2006, Jørgensen et al. 2007, Heino et al. 2015). The great meaning and the potential of our understanding of the sources of evolution of life history traits for understanding ecosystem functioning is the main motivation of my research presented in this thesis.

In my thesis I combine theoretical models and empirical work. I aimed at testing hypotheses on the evolution of life history traits in the context of one of the key life history compromises: the evolutionary trade-off between current and future reproduction (Williams 1966). My work was inspired by life histories of species living at a high-latitude Arctic ecosystem of Svalbard archipelago. The empirical part of my thesis, performed to test the predictions of my theoretical research, was conducted in Svalbard in years 2015 2020. The research questions regarding the evolution of body size, growth rate, mode of reproduction and, timing and synchrony of breeding presented in this thesis are oriented around the two subjects described below: the life history trade-off between current and future reproduction under temporal constraints generally and in a high latitude Arctic ecosystem particularly.