Onkelinx, ThierryResearch Institute for Nature and Forest (INBO), Brussels, Belgium
Martin, Gilles SanBehavioural Ecology and Conservation group, Biodiversity Research Centre, Earth and Life Institute, Universite catholique de Louvain, Louvain-la-Neuve, Belgium
Brown, Peter M. J.Animal & Environmental Research Group, Department of Life Sciences, Anglia Ruskin University, Cambridge, UK
Hautier, LouisUnité Protection des plantes et écotoxicologie, Département Sciences du vivant, Centre wallon de Recherches agronomiques, Gembloux, Belgium - Lutte biologique et Ecologie spatiale (Biological Control and Spatial Ecology Lab, Université Libre de Bruxelles, Belgium
Nedvěd, OldrichFaculty of Biological Sciences and Institute of Entomology, University of South Bohemia, Academy of Sciences of the Czech Republic, České Budějovice, Czech Republic
Ravn, Hans PeterUniversity of Copenhagen, Forest & Landscape, Frederiksberg C. Denmark
Grégoire, Jean ClaudeLutte biologique et Ecologie spatiale (Biological Control and Spatial Ecology Lab, Université Libre de Bruxelles, Belgium
English
Aim Invasive alien species (IAS) are recognized as major drivers of biodiversity loss, but few causal relationships between IAS and species declines have been documented. In this study, we compare the distribution (Belgium and Britain) and abundance (Belgium, Britain and Switzerland) of formerly common and widespread native ladybirds before and after the arrival of Harmonia axyridis, a globally rapidly expanding IAS.Location EuropeMethods We used generalized linear mixed-effects models (GLMMs) to assess the distribution trends of eight conspicuous and historically widespread and common species of ladybird within Belgium and Britain before and after the arrival of H. axyridis. The distribution data were collated largely through public participatory surveys but verified by a recognized expert. We also used GLMMs to model trends in the abundance of ladybirds using data collated through systematic surveys of deciduous trees in Belgium, Britain and Switzerland.Results Five (Belgium) and seven (Britain) of eight species studied show substantial declines attributable to the arrival of H. axyridis. Indeed, the two-spot ladybird, Adalia bipunctata, declined by 30% (Belgium) and 44% (Britain) over 5 years after the arrival of H. axyridis. Trends in ladybird abundance revealed similar patterns of declines across three countries.Main conclusion Together, these analyses show H. axyridis to be displacing native ladybirds with high niche overlap, probably through predation and competition. This finding provides strong evidence of a causal link between the arrival of an IAS and decline in native biodiversity. Rapid biotic homogenization at the continental scale could impact on the resilience of ecosystems and severely diminish the services they deliver.