Behavioural trade‐offs between growth and mortality explain evolution of submaximal growth rates

Abstract

Summary1. The importance of body size and growth rate in ecological interactions is widely recognized, and both are frequently used as surrogates for fitness. However, if there are significant costs associated with rapid growth rates then its fitness benefits may be questioned. 2. In replicated whole-lake experiments, we show that a domestic strain of rainbow trout (artificially selected for maximum intrinsic growth rate) use productive but risky habitats more than wild trout. Consequently, domestic trout grow faster in all situations, experience greater survival in the absence of predators, but have lower survival in the presence of predators. Therefore, rapid growth rates are selected against due to increased foraging effort (or conversely, lower antipredator behaviour) that increases vulnerability to predators. In other words, there is a behaviourally mediated trade-off between growth and mortality rates. 3. Whereas rapid growth is beneficial in many ecological interactions, our results show the mortality costs of achieving it are large in the presence of predators, which can help explain the absence of an average phenotype with maximized growth rates in nature.

Behavioural mediation of the costs and benefits of fast growth in a marine fish

“…This is often difficult in behavioural studies, which may account for the relative paucity of data. Although there are few studies, evidence for growth-mortality trade-offs has been documented in a wide variety of taxa including damselflies (Stoks et al 2005), rainbow trout (Biro et al 2004(Biro et al , 2006 and house mice, Mus musculus (Biro & Stamps 2008). However, our study shows that correlations among behavioural and growth traits do not necessarily provide evidence of growth-mortality trade-offs and that spatial and temporal variation in the direction of growth-selective processes might be sufficient to produce both consistent variability in growth patterns among individuals and submaximal growth rates of populations.…”

“…This occurred because fast-growing fish were more likely to use habitats that were more productive in terms of food resources, but placed the fast-growing fish at greater risk of predation than the habitats used by slow-growing individuals (Biro et al 2006). Such trade-offs are thought to explain the evolution of submaximal growth rates in wild populations of fishes (Biro et al 2004(Biro et al , 2006 and other animals (Stoks et al 2005).…”

“…As all animals are prey, at least during their early life history stages, greater foraging effort can increase the visibility of prey to predators with a concomitant increase in the probability of mortality. Evidence for the role of behaviour comes from a variety of sources (reviewed in Stamps 2007;Biro & Stamps 2008), including recent studies in lake systems that have shown that fast-growing rainbow trout, Oncorhynchus mykiss, that had high foraging rates were preferentially removed by predators (Biro et al 2004(Biro et al , 2006. This occurred because fast-growing fish were more likely to use habitats that were more productive in terms of food resources, but placed the fast-growing fish at greater risk of predation than the habitats used by slow-growing individuals (Biro et al 2006).…”

“…Evidence for the role of behaviour comes from a variety of sources (reviewed in Stamps 2007;Biro & Stamps 2008), including recent studies in lake systems that have shown that fast-growing rainbow trout, Oncorhynchus mykiss, that had high foraging rates were preferentially removed by predators (Biro et al 2004(Biro et al , 2006. This occurred because fast-growing fish were more likely to use habitats that were more productive in terms of food resources, but placed the fast-growing fish at greater risk of predation than the habitats used by slow-growing individuals (Biro et al 2006). Such trade-offs are thought to explain the evolution of submaximal growth rates in wild populations of fishes (Biro et al 2004(Biro et al , 2006 and other animals (Stoks et al 2005).…”

Rainbow trout in seasonal environments: phenotypic trade‐offs across a gradient in winter duration

“…2004; Biro et al. 2006), and their overwinter survival is dependent on a minimum threshold quantity of energy storage (Biro et al. 2004b, 2005; Mogensen and Post 2012).…”