Invasion by a non‐native ecosystem engineer alters distribution of a native predator

Abstract

Aim Shifts in diet composition, abundance or distribution of native predators can occur as a result of exotic prey introductions. We examined effects of non‐native earthworms and anthropogenic landscape disturbance on habitat selection by the American robin (Turdus migratorius), a generalist predator, at landscape and local levels. We also investigated whether robins could act as vectors of spread for earthworm cocoons (egg cases). Location Boreal forest of Alberta, Canada. Methods We conducted robin and earthworm surveys at campgrounds, well pads, roads, pipelines, seismic lines and forest interiors across northern Alberta. At a subset of paired locations that had similar habitats and anthropogenic disturbance levels, we sampled both robins and earthworms. Results Both groups were most likely to occur at campgrounds, well pads and roads. Furthermore, robins were more likely to occur at locations where earthworms were present in our paired local‐level surveys. This correlation between robin and earthworm distributions could be due to robins acting as a vector for earthworm spread, rather than robins’ use of earthworms as prey. However, in tests using captive robins, earthworm cocoons did not survive digestion. Main conclusions Robin and earthworm distributions were correlated, likely due to robins’ use of earthworms as prey. These results suggest exotic prey can strongly influence native predators at both landscape and local levels, with shifts in native predator distributions occurring as a result of spatial variability in exotic prey distributions. Although the impacts of ecosystem engineering by earthworms have been previously demonstrated, our study provides evidence that effects of earthworms can also cascade upwards via trophic interactions.

Side‐swiped: ecological cascades emanating from earthworm invasions

“…). For birds, invasive earthworms can provide a novel food source, and invasions altered distribution of a generalist avian predator at local and landscape scales (Cameron and Bayne ). Invasive earthworms also indirectly affect wildlife by altering habitat structure.…”

Integrating movement ecology with biodiversity research - exploring new avenues to address spatiotemporal biodiversity dynamics

“…of big mammals or herbivorous birds, which affects nutrient cycling, biomass production, disturbance regimes and consequently plant species composition [ 10 , 62 ]), or predation (e.g. [ 63 ]).…”

Characteristic and derived diversity: implementing the species pool concept to quantify conservation condition of habitats

“…Human-related changes in environmental conditions and dramatically enhanced dispersal over great geographic distances have provided the opportunity for species to establish in communities where they were previously absent (Hobbs et al, 2009;Cameron & Bayne, 2012). In this context, the invasion by non-native species has received the most attention due to its unambiguous anthropogenic cause, observable and strong effects on ecosystems (Sax & Gaines, 2003;Vil a et al, 2011) and negative public perception (Simberloff et al, 2013).…”