Abstract
Invasive alien species impacts might be mediated by environmental factors such as climatic warming. For invasive predators, multiple predator interactions could also exacerbate or dampen ecological impacts. These effects may be especially pronounced in highly diverse coastal ecosystems that are prone to profound and rapid regime shifts. We examine emergent effects of warming on the strength of intraspecific multiple predator effects from a highly successful invasive gammarid Gammarus tigrinus, using a functional response approach towards larval chironomids (feeding rates under different prey densities). Single predator maximum feeding rates were three-times higher at 24 °C compared to 18 °C overall, with potentially prey destabilising type II functional responses exhibited. However, pairs of gammarids exhibited intraspecific multiple predator effects that were in turn mediated by temperature regime, whereby synergisms were found at the lower temperature (i.e. positive non-trophic interactions) and antagonisms detected at the higher temperature (i.e. negative non-trophic interactions) under high prey densities. Accordingly, warming scenarios may worsen the impact of this invasive alien species, yet implications of temperature change are dependent on predator–predator interactions. Emergent effects between abiotic and biotic factors should be considered in ecological impact predictions across habitat types for invasive alien species.
Highlights
Ecological impacts from a notorious invasive alien species in marine, brackish and freshwater habitats were shown to be mediated through intraspecific multiple predator effects between two temperatures and across a prey density gradient in the present study
Page 5 of 7 35 interaction strengths with a representative benthic prey (Pellan et al 2016), corroborating previous studies on gammarid congenerics (Laverty et al 2017), emergent effects that mediate invader impacts were found according to temperature and prey density
Intraspecific multiple predator interactions eroded the magnitude of positive temperature effects on feeding rates
Summary
Biological invasions are a major driver of global biodiversity loss through ecological impacts that disrupt the functioning of natural systems (Vilà et al 2011; Simberloff et al 2013; Dick et al 2017). Whilst key drivers of change, the success and impacts of invasive alien species can be mediated by other human-induced alterations, such as habitat and climate changes (Didham et al 2005; Pyšek et al 2020). Context-dependencies present a major challenge to ecological impact prediction (Ricciardi et al 2013), with. Advances have recently paralleled quantifications of invasive species functional responses with the magnitude of their infield ecological impact (Dick et al 2014). The functional response approach quantifies resource use of a consumer as a function of resource density, allowing for comparative elucidation of density-dependences in ecological impacts under a range of abiotic variables The functional response approach quantifies resource use of a consumer as a function of resource density, allowing for comparative elucidation of density-dependences in ecological impacts under a range of abiotic variables (e.g., warming; Wasserman et al. Vol.:(0123456789)
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