Predicting invasive species impacts: a community module functional response approach reveals context dependencies

Abstract

SummaryPredatory functional responses play integral roles in predator–prey dynamics, and their assessment promises greater understanding and prediction of the predatory impacts of invasive species. Other interspecific interactions, however, such as parasitism and higher-order predation, have the potential to modify predator–prey interactions and thus the predictive capability of the comparative functional response approach. We used a four-species community module (higher-order predator; focal native or invasive predators; parasites of focal predators; native prey) to compare the predatory functional responses of native Gammarus duebeni celticus and invasive Gammarus pulex amphipods towards three invertebrate prey species (Asellus aquaticus, Simulium spp., Baetis rhodani), thus, quantifying the context dependencies of parasitism and a higher-order fish predator on these functional responses. Our functional response experiments demonstrated that the invasive amphipod had a higher predatory impact (lower handling time) on two of three prey species, which reflects patterns of impact observed in the field. The community module also revealed that parasitism had context-dependent influences, for one prey species, with the potential to further reduce the predatory impact of the invasive amphipod or increase the predatory impact of the native amphipod in the presence of a higher-order fish predator. Partial consumption of prey was similar for both predators and occurred increasingly in the order A. aquaticus, Simulium spp. and B. rhodani. This was associated with increasing prey densities, but showed no context dependencies with parasitism or higher-order fish predator. This study supports the applicability of comparative functional responses as a tool to predict and assess invasive species impacts incorporating multiple context dependencies.

Assessing the ecological impacts of invasive species based on their functional responses and abundances

“…Alexander et al 2014a, b;Dick et al 2013Dick et al , 2017Paterson et al 2014;Laverty et al 2015;Xu et al 2016) have shown that the comparative FR methodology is rapid, efficient and effective at explaining and predicting the ecological damage caused by invasive species. However, in some cases the FR of invasive species is unremarkable when compared to those of native species, yet ecological damage is known to occur, as is the case with N. melanostomus and P. parva toward invaded communities (Barton et al 2005;Britton et al 2010;Gozlan et al 2010;Pagnucco and Ricciardi 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)

“…This method has been pioneered for the prediction of invasive species impacts in comparison to trophically analogous native species Paterson et al 2015;Dick et al 2017). It is particularly useful in assessing ecological impact under a number of abiotic contexts (e.g.…”

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

“…Curves were bootstrapped to visualise variability (n = 1999), and the parameters a and h compared between amphipod groups (within each prey type) and prey types (within amphipod groups) using indicator variables (function frair_compare; Juliano 2001; Paterson et al 2014). …”

“…The aim of these experiments was to quantify predator FRs, modelling the relationship between resource use and availability (Holling 1959;Dick et al 2013). This methodology for comparing invasive and native species' impacts is becoming widely adopted and is accumulating supporting evidence (Haddaway et al 2012;Dick et al 2013;Alexander et al 2014;Paterson et al 2014;Dick et al 2014).…”