Form of an evolutionary tradeoff affects eco-evolutionary dynamics in a predator–prey system

Abstract

Evolution on a time scale similar to ecological dynamics has been increasingly recognized for the last three decades. Selection mediated by ecological interactions can change heritable phenotypic variation (i.e., evolution), and evolution of traits, in turn, can affect ecological interactions. Hence, ecological and evolutionary dynamics can be tightly linked and important to predict future dynamics, but our understanding of eco-evolutionary dynamics is still in its infancy and there is a significant gap between theoretical predictions and empirical tests. Empirical studies have demonstrated that the presence of genetic variation can dramatically change ecological dynamics, whereas theoretical studies predict that eco-evolutionary dynamics depend on the details of the genetic variation, such as the form of a tradeoff among genotypes, which can be more important than the presence or absence of the genetic variation. Using a predator-prey (rotifer-algal) experimental system in laboratory microcosms, we studied how different forms of a tradeoff between prey defense and growth affect eco-evolutionary dynamics. Our experimental results show for the first time to our knowledge that different forms of the tradeoff produce remarkably divergent ecoevolutionary dynamics, including near fixation, near extinction, and coexistence of algal genotypes, with quantitatively different population dynamics. A mathematical model, parameterized from completely independent experiments, explains the observed dynamics. The results suggest that knowing the details of heritable trait variation and covariation within a population is essential for understanding how evolution and ecology will interact and what form of eco-evolutionary dynamics will result.allele-specific quantitative PCR | Chlorella vulgaris | clonal models | grazing resistance | rapid evolution E volutionary dynamics, changes in intraspecific genotype frequency over generations, can have a time scale similar to that of ecological dynamics (1-3). Selection mediated by ecological interactions causes evolutionary dynamics, and evolution of traits, in turn, changes ecological interactions. Thus, understanding population dynamics needs to take account of the feedbacks between trait evolution and ecological interactions (i.e., eco-evolutionary feedbacks). These feedbacks have increasingly attracted ecologists' attention since Pimentel (4) proposed genetic feedback as a mechanism regulating animal populations (e.g., refs. 5-11). This integration of evolutionary biology and ecology has important implications in both basic and applied problems in biology (12)(13)(14)(15)(16)(17).Empirical studies have shown that rapid evolution can affect many ecological interactions, including predator-prey (18-20), host-parasite (21), herbivore-plant (22), competitive interactions (23), and interactions with abiotic environments (24-27). Previous empirical studies on eco-evolutionary feedbacks have usually compared the dynamics of populations with and without genetic variation, but recent theoretic...

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

“…The trait range where this competitive exclusion of the undefended prey occurred was strongly reduced by the post‐attack defense, while the trait range allowing coexistence increased in comparison with a noninterfering pre‐attack defense due to indirect facilitation. The relevance of our results is supported by empirical studies revealing that low to intermediate defense levels frequently occur in nature (White, Kaul, Knoll, Wilson, & Sarnelle, 2011) and that defended prey types may outcompete undefended prey types even if they have costs for their defense (Kasada et al., 2014). The presented mechanism of indirect facilitation among prey species may provide an explanation why apparent competition, that is, an increasing density of one prey species indirectly reduces the density of the other prey species via the predator (Holt, 1977), is not always observed in nature (Chaneton & Bonsall, 2000).…”

“…Furthermore, the type of defense costs regarding competitiveness (resource uptake affinity or growth rate) plays an important role for coexistence. Theory already showed that predator‐mediated coexistence crucially depends on the environmental conditions (Chase et al., 2002), for example, the enrichment level (Genkai‐Kato & Yamamura, 1999; Leibold, 1996; Proulx & Mazumder, 1998), the prey switching behavior of the predator (Abrams & Matsuda, 1993; Fryxell & Lundberg, 1994; Murdoch, 1969), the magnitude of the trade‐off between defense and competitiveness (Abrams, 1999; Kasada, Yamamichi, & Yoshida, 2014; Tirok & Gaedke, 2010), and the difference in both the defense level and the competitiveness between the prey types (Becks, Ellner, Jones, & Hairston, 2010; Ehrlich, Becks, & Gaedke, 2017; Jones & Ellner, 2007). However, the role of different defense mechanisms and competition costs in prey communities remains unclear but holds promise to be decisive for their coexistence and the occurring population dynamics.…”

“…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.…”

Experimental evidence that parasites drive eco-evolutionary feedbacks

“…Whereas this perspective has recently received much attention (e.g., refs. [5][6][7][8], little is known about how interactions between organismal traits and biotic as well as abiotic drivers of ecosystem change govern the occurrence and strength of these feedbacks (9).…”

How (co)evolution alters predator responses to increased mortality: extinction thresholds and hydra effects

“…Plankton microcosms have been used previously to study eco-evolutionary dynamics, e.g., how prey evolution alters the population-level dynamics of predator-prey systems (Yoshida et al 2003, Becks et al 2010, Kasada et al 2014). Plankton microcosms have been used previously to study eco-evolutionary dynamics, e.g., how prey evolution alters the population-level dynamics of predator-prey systems (Yoshida et al 2003, Becks et al 2010, Kasada et al 2014).…”