Comparison of the functional responses of invasive and native amphipods

Abstract

While we can usually understand the impacts of invasive species on recipient communities, invasion biology lacks methodologies that are potentially more predictive. Such tools should ideally be straightforward and widely applicable. Here, we explore an approach that compares the functional responses (FRs) of invader and native amphipod crustaceans. Dikerogammarus villosus is a PontoCaspian amphipod currently invading Europe and poised to invade North America. Compared with other amphipods that it actively replaces in freshwaters, D. villosus exhibited significantly greater predation, consuming significantly more prey with a higher type II FR. This corroborates the known dramatic field impacts of D. villosus on invaded communities. In another species, FRs were nearly identical in invasive and native ranges. We thus propose that if FRs of other taxa and trophic groups follow such general patterns, this methodology has potential in predicting future invasive species impacts.

Advancing impact prediction and hypothesis testing in invasion ecology using a comparative functional response approach

“…Although functional responses have been used to evaluate the biological control potential of introduced parasitoids (Greenberg et al 2001;Jones et al 2003), the first explicit test of the hypothesis that a known ecologically damaging invader might display a higher functional response than native and other less damaging invaders was by Bollache et al (2008), who showed that the invasive 'killer shrimp', Dikerogammarus villosus, had a higher Type II functional response than other native and introduced comparator species in Europe. Dick et al (2010) then used the comparative functional response method within an invasive species, showing that an invasive predatory amphipod, Gammarus pulex, had a higher Type II functional response when parasitized with an acanthocephalan worm, counter to the enemy release hypothesis, illustrating the utility of the method in tests of major invasion biology hypotheses (see below).…”

“…Authors then began explicitly comparing invader and native species with functional responses, such as Haddaway et al (2012), who showed an invasive crayfish has a higher functional response than a native. However, this study, as with most others (see Bollache et al 2008;Dick et al 2010), did not explicitly link differential functional responses to actual field patterns of impact on particular prey species; rather, the prey species were chosen to illustrate the methodology and general pattern of higher functional responses of invaders compared to natives. More recently, however, Dick et al (2013) demonstrated that the invasive 'bloody red' shrimp Hemimysis anomala has a higher functional response to several prey species than trophically analogous native species (that are also themselves invasive in some regions) and, more intriguingly, that the greatest invader/native differentials in functional responses were associated with the greatest field impacts of the invader (Fig.…”

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)

“…Suitability of each model was compared with Akaike Information Criterion (AIC). Functional responses were then fitted using maximum likelihood estimation (MLE; Bolker 2010) and the Lambert W function (Bolker 2008).…”

“…Functional response refers to the rate of consumption of a resource with regards to resource density (Solomon 1949;Holling 1959). It is clear that species with a higher functional response (e.g., higher attack rates, lower handling times, higher asymptote) have a higher impact potential (Bollache et al 2008;Haddaway et al 2012;Dick et al 2013). Functional responses are categorised into: the Type I rectilinear response, usually only found in filter feeders where resource consumption is not limited by handling time (Jeschke et al 2004); the Type II inversely density dependent response with high prey consumption at low densities; and Type III sigmoidal, positively density dependent response whereupon prey have a low-density refuge (Oaten and Murdoch 1975).…”

Substrate preferences of coexisting invasive amphipods, Dikerogammarus villosus and Dikerogammarus haemobaphes, under field and laboratory conditions

“…A second invasive amphipod, Dikerogammarus villosus (killer shrimp), was first recorded in the UK 2010 (MacNeil et al 2010) and to date is geographically confined to five known locations (GBNNSS 2017). It is likely that the geographical distribution of this species will expand in the future across the globe (Kobak et al 2016) and it is anticipated that it is only a matter of time before D. villosus invades North America (Bollache et al 2008).…”