Rapid evolution drives ecological dynamics in a predator–prey system

Abstract

Ecological and evolutionary dynamics can occur on similar timescales. However, theoretical predictions of how rapid evolution can affect ecological dynamics are inconclusive and often depend on untested model assumptions. Here we report that rapid prey evolution in response to oscillating predator density affects predator-prey (rotifer-algal) cycles in laboratory microcosms. Our experiments tested explicit predictions from a model for our system that allows prey evolution. We verified the predicted existence of an evolutionary tradeoff between algal competitive ability and defence against consumption, and examined its effects on cycle dynamics by manipulating the evolutionary potential of the prey population. Single-clone algal cultures (lacking genetic variability) produced short cycle periods and typical quarter-period phase lags between prey and predator densities, whereas multi-clonal (genetically variable) algal cultures produced long cycles with prey and predator densities nearly out of phase, exactly as predicted. These results confirm that prey evolution can substantially alter predator-prey dynamics, and therefore that attempts to understand population oscillations in nature cannot neglect potential effects from ongoing rapid evolution.

Not attackable or not crackable—How pre‐ and post‐attack defenses with different competition costs affect prey coexistence and population dynamics

“…The Monod equation is equivalent to a Holling type II functional response but is not restricted to predator—prey interactions and has been applied also to autotrophic organisms taking up nutrients (e.g., Becks et al., 2010; Raatz, Gaedke, & Wacker, 2017; Yoshida et al., 2003). The per capita growth rate of A i in dependence of N is described by…”

“…TVC, Typical values used in chemostat experiments with rotifers and algae as they enable sufficient rotifer densities but avoid light limitation (e.g., Becks et al., 2010; Yoshida et al., 2003); NM, No measurements available. For simplicity, we assume that the fraction of T spent for attacking and manipulating the prey is equal, that is, c a  = 0.5 (sensitivity analysis in Appendix S3).…”

“…Previous studies on predator‐mediated coexistence in diamond‐shaped food web models often implicitly assumed pre‐attack defenses (Abrams, 1999; Fryxell & Lundberg, 1994; Yamauchi & Yamamura, 2005) and considered either a higher half‐saturation constant (Becks et al., 2010; Jones & Ellner, 2007; Yoshida, Jones, Ellner, Fussmann, & Hairston, 2003) or a lower maximum growth rate as costs (Abrams, 1999; Kasada et al., 2014; Yoshida et al., 2007). In this study, we explicitly model pre‐attack and post‐attack defenses and both cost types.…”

Long-term transients and complex dynamics of a stage-structured population with time delay and the Allee effect

“…Understanding the aspects and tendencies of complex population dynamics observed in natural ecosystems (Ellner and Turchin, 1995;Ranta et al, 1995;Widdicombe et al, 2010) as well as in the laboratory (Costantino et al, 1997;Yoshida et al, 2003;Becks et al 2005) is important for both theoretical and practical reasons, and indeed it has been a central point of ecological research for several decades (Nicholson, 1954;Luckinbill, 1974;Turchin, 2003;Odum and Barrett, 2004;Begon et al, 2005). Whilst empirical studies provide invaluable information such as, for instance, examples of different dynamics (Becks et al 2005;Yoshida et al, 2003), a theoretical approach is necessary in order to generalize and systematize the results of field observations or lab experiments.…”

“…Whilst empirical studies provide invaluable information such as, for instance, examples of different dynamics (Becks et al 2005;Yoshida et al, 2003), a theoretical approach is necessary in order to generalize and systematize the results of field observations or lab experiments. In particular, mathematical modelling is proved to be an efficient research tool that helps to reveal ecosystem properties when replicated experiments under controlled conditions are not possible (Maynard Smith 1974;Bjornstad and Grenfell, 2001;Turchin, 2003).…”