Invasive alien predator causes rapid declines of native European ladybirds
Article first published online: 7 FEB 2012
© 2012 Blackwell Publishing Ltd
Diversity and Distributions
Volume 18, Issue 7, pages 717–725, July 2012
How to Cite
Roy, H. E., Adriaens, T., Isaac, N. J. B., Kenis, M., Onkelinx, T., Martin, G. S., Brown, P. M. J., Hautier, L., Poland, R., Roy, D. B., Comont, R., Eschen, R., Frost, R., Zindel, R., Van Vlaenderen, J., Nedvěd, O., Ravn, H. P., Grégoire, J.-C., de Biseau, J.-C. and Maes, D. (2012), Invasive alien predator causes rapid declines of native European ladybirds. Diversity and Distributions, 18: 717–725. doi: 10.1111/j.1472-4642.2012.00883.x
- Issue published online: 7 JUN 2012
- Article first published online: 7 FEB 2012
- Biological control;
- biological invasions;
- citizen science;
- Harmonia axyridis;
- population decline
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.
Methods 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.