Predator‐free space, functional responses and biological invasions

Abstract

Summary1. Predator-prey interactions are mediated by the structural complexity of habitats, but disentangling the many facets of structure that contribute to this mediation remains elusive. In a world replete with altered landscapes and biological invasions, determining how structure mediates the interactions between predators and novel prey will contribute to our understanding of invasions and predator-prey dynamics in general. 2. Here, using simplified experimental arenas, we manipulate predator-free space, whilst holding surface area and volume constant, to quantify the effects on predator-prey interactions between two resident gammarid predators and an invasive prey, the Ponto-Caspian corophiid Chelicorophium curvispinum. 3. Systematically increasing predator-free space alters the functional responses (the relationship between prey density and consumption rate) of the amphipod predators by reducing attack rates and lengthening handling times. Crucially, functional response shape also changes subtly from destabilizing Type II towards stabilizing Type III, such that small increases in predatorfree space to result in significant reductions in prey consumption at low prey densities. 4. Habitats with superficially similar structural complexity can have considerably divergent consequences for prey population stability in general and, particularly, for invasive prey establishing at low densities in novel habitats.

Predicting predatory impact of juvenile invasive lionfish (Pterois volitans) on a crustacean prey using functional response analysis: effects of temperature, habitat complexity and light regimes

“…In our study, while both complexities revealed a Type II response; low complexity had a non-significantly higher attack rate, while high complexity had a non-significantly lower handling time. This can be attributed to habitats with a high degree of structural integrity limiting a predator's efficiency by interfering with detection of prey and the ability of the predator to catch the prey (Greene 1986;James and Heck 1994; Barrios-O'Neill et al 2015). This occurs through a variety of mechanisms; the formation of a physical barrier causes disruptive implications for visual (Manatunge et al 2000;Warfe and Barmuta 2004) and olfactory signals (Ferner et al 2009), furthermore physical structure can provide complete or partial refuge for prey from predators (Finke and Denno 2006;Horinouchi 2007).…”

“…This occurs through a variety of mechanisms; the formation of a physical barrier causes disruptive implications for visual (Manatunge et al 2000;Warfe and Barmuta 2004) and olfactory signals (Ferner et al 2009), furthermore physical structure can provide complete or partial refuge for prey from predators (Finke and Denno 2006;Horinouchi 2007). In addition, a predator's ability to maneuver within a structure is often impaired (Winfield 1986;Bartholomew et al 2000;Barrios-O'Neill et al 2015). Therein, it is a general assumption that the foraging efficiency of predators ought to decrease with increasing habitat complexity (Radomski and Goeman 2001;, thus effectively dampening the strength of the functional response.…”

“…While the experimental set up used in the present study could be considered limited it gives an insight into the complex ways in which habitat mediates behaviour. Further investigation of the effect of habitat complexity on predation by using fractal dimensions and predator free space (Barrios-O'Neill et al 2015) may provide further insight into the effects of structure in lionfish predation. Light regimes are a strong modulator of animal behaviour (Schwalbe and Webb 2015).…”

Effects of acute and chronic temperature changes on the functional responses of the dogfish Scyliorhinus canicula (Linnaeus, 1758) towards amphipod prey Echinogammarus marinus (Leach, 1815)

“…Thermal responses are understood to be an underlying mechanism behind predator -prey dynamics (Berlow et al 2009;Rall et al 2010;Englund et al 2011), but predicting the outcome of such interactions under future abiotic scenarios is highly problematic (Le Quesne and Pinnegar 2011). This is partly due to multiple layers of real world complexities such as habitat heterogeneity (MacNeil et al 2004;Ferner et al 2009;Alexander et al 2015;Barrios-O'Neill et al 2015), light (Koski and Johnson 2002), multiple predator effects (Lang et al 2012;Alexander et al 2013;Wasserman et al 2016a). The apparent species specificity of thermal dynamics poses an additional layer of difficulty in response prediction due to the metabolism of different species having varying sensitivity to temperature effects and therefore producing differential responses (Lang et al 2012).…”

Size matters: predation of fish eggs and larvae by native and invasive amphipods

“…The low consumption of larvae probably reflects an interaction between predator size, prey type and substrate. The largest amphipods are less able to manoeuvre through interstitial spaces, but motile prey can make best use of these spaces to evade predation (Barrios-O'Neill et al 2015). However, it is not clear why low consumption of larvae should be associated with low overall consumption i.e.…”