Co-evolution as an important component explaining microbial predator-prey interaction

Abstract

Predator-prey relationships belong to the most important and well-studied ecological interactions in nature. Understanding the underlying mechanisms is important to predict community dynamics and to estimate coexistence probability. Historically, evolution has been considered to be too slow to affect such ecological interactions. However, evolution can occur within ecological time scales, potentially affecting predator-prey communities. In an antagonistic pair-wise relationship the prey might evolve to minimize the effect caused by the predator (e.g. mortality), while the predator might evolve to maximize the effect (e.g. food intake). Evolution of one of the species or even co-evolution of both species in predator-prey relationships is often difficult to estimate from population dynamics without measuring of trait changes in predator and/or prey population. Particularly in microbial systems, where microorganisms evolve quickly, determining whether co-evolution occurs in predator-prey systems is challenging. We simulate observational data using quantitative trait evolution models and show that the interaction between bacteria and ciliates can be best explained as a co-evolutionary process, where both the prey and predator evolve. Evolution by prey alone explains the data less well, whereas the models with predator evolution alone or no evolution are both failing. We conclude that that ecology and evolution both interact in shaping community dynamics in microcosms. Ignoring the contribution of evolution might lead to incorrect conclusions.

Mortality and coexistence time both cause changes in predator-prey co-evolutionary dynamics

“…The predator densities decrease over time as prey gets better 130 defended against attack. Coevolution of the predatory attack rates prevents further decrease 131 in the predator densities [25] and the community stabilizes after a few transfers. This suggests 132 arms-race dynamics [26] where the defence and attack traits evolutionarily increase during 133 this experiment [25].…”

“…If global mortality 103 is high (small transfer volume) the time both partners interact is shorter because initial 104 densities are lower and encounter rate is reduced, which may mean reduced strength of 105 natural selection, whereas a low mortality may place both partners in close contact from the 106 beginning of the experiment and intensify interaction. 107 Expanding our previous model [25] we report how global mortality and time of coexistence 108 affect predator-prey communities and expand the prior literature by exploring scenarios 109 impractical in experimental studies. Our theoretical findings suggest that both, mortality and 110 coexistence time, have effects on the community.…”

“…Here, we present such an approach taking advantage of a mathematical model simulating 80 microbial predator-prey dynamics [25]. A recent experimental study tracked interaction 81 between Pseudomonas fluorescens bacteria as prey and Tetrahymena thermophila ciliates 82 as predators, to investigate ecological and evolutionary dynamics [14].…”

“…previously built a mathematical model [25] and simulated the observed predator-prey 86 dynamics, but kept the parameters transfer volume and transfer interval the same as in the 87 experimental study [14]. This model allows us to track ecological dynamics in form of predator 88 and prey densities and reveals how prey species evolve anti-predator defence traits and how 89 predator species evolutionary increase their predation efficiency.…”

Evolution in interacting species alters predator life history traits, behavior and morphology in experimental microbial communities

“…First, the pronounced impairment of predator growth traits upon prey evolution together with the lack of clear improvements in the ability of evolved predators to feed on ancestral prey types corroborate the asymmetric selection hypothesis. Second, the occurrence of predator evolution in other key traits for predator-prey interaction despite this suggests that tracking ecological changes alone may result in an underestimation of predator evolution (see also [50]). Further studies are required to identify the factors producing this constraint, such as offense-growth tradeoffs or the specificity of the advantage of improved offense to defended prey types.…”