Abstract
The effects of asymmetric interactions on population dynamics has been widely investigated, but there has been little work aimed at understanding how life history parameters like generation time, life expectancy and the variance in lifetime reproductive success are impacted by different types of competition. We develop a new framework for incorporating trait‐mediated density‐dependence into size‐structured models and use Trinidadian guppies to show how different types of competitive interactions impact life history parameters. Our results show the degree of symmetry in competitive interactions can have dramatic effects on the speed of the life history. For some vital rates, shifting the competitive superiority from small to large individuals resulted in a doubling of the generation time. Such large influences of competitive symmetry on the timescale of demographic processes, and hence evolution, highlights the interwoven nature of ecological and evolutionary processes and the importance of density‐dependence in understanding eco‐evolutionary dynamics.
Highlights
IntroductionFor example larger individuals in many animal species are more likely to acquire territories, gain initial access to resources, or acquire a mate, compared to those that are smaller
We describe the population dynamic consequences of changing the nature of competition from a scenario where smaller individuals are competitively superior (φ < 0) to one wherein larger individuals are competitively superior (φ > 0) in each function within our integral projection model (IPM)
Density-dependence is an old concept in biology and different assumptions about the underlying mechanisms lead to very different population dynamics (Geritz & Kisdi 2004; Br€annstro€m & Sumpter 2005)
Summary
For example larger individuals in many animal species are more likely to acquire territories, gain initial access to resources, or acquire a mate, compared to those that are smaller. Such extremely asymmetric interactions are at one end of a continuum (Nicholson 1954; Varley et al 1973; Hassell 1975; Weiner 1990). There has been considerable work using simple unstructured models to explore the population dynamical consequences of symmetric vs asymmetric competition as well as competition that lies along the continuum between them (Maynard Smith & Slatkin 1973; Hassell 1975; Br€annstro€m & Sumpter 2005; Anazawa 2010, 2012). There has been much less work considering the life history consequences of different forms of competition and whether these depend upon which aspects of the demography are affected by competition
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