Harmonia axyridis implicated in native European ladybird declines

Rates of global extinction are accelerating and show no sign of slowing (Millenium Ecosystem Assessment 2005). Invasive alien species (IAS) are recognised as major drivers of biodiversity loss (Winter et al. 2009). IAS afford a unique opportunity to accurately assess threats to biodiversity because the time at which an IAS arrives within an ecosystem is often known, unlike other drivers of change. However, few causal relationships between IAS and species declines have been documented. We used data collated through extensive citizen-driven field surveys in Belgium and Britain spanning decades, as well as intensive monitoring by scientists in Belgium, Britain and Switzerland. The fine-scale data collection, replicated in time (over decades and including detailed observations before and after the arrival of an IAS) and with extensive coverage in three European countries, combined with powerful modern mixed-modelling (statistical) techniques, provided a uniquely rigorous test of the impacts of an IAS on biodiversity. We report rapid, dramatic and ongoing declines in the distribution of formerly common and widespread native ladybirds in Belgium and Britain following the arrival of Harmonia axyridis, a globally rapidly expanding IAS (Roy et al. 2012). For example, the two-spot ladybird, Adalia bipunctata, declined in both Belgium and Britain over five years after the arrival of H. axyridis. Trends in ladybird abundance revealed similar patterns of declines across three countries. These analyses implicate H. axyridis in the displacement of native ladybirds, particularly those with a high niche (habitat and diet) overlap. There is considerable debate over the relationship between species diversity and ecosystem processes (Rey Benayas et al. 2009). Studies indicate that species diversity enhances productivity and stability in some ecosystems, but not in others. However, it is difficult to predict which species are critical to ecosystem function and rapid biotic homogenisation at the continental scale could diminish the resilience of ecosystems and the services they deliver. This research is published in full within the journal Diversity and Distributions (Roy et al. 2012). References: Millenium Ecosystem Assessment (2005) Ecosystems and human well-being: current state and trends. World Resources Institute, Washington, DC; Rey Benayas JM, Newton AC, Diaz A, Bullock JM (2009) Enhancement of biodiversity and ecosystem services by ecological restoration: a meta-analysis. Science 325: 1121-1124; Roy HE, Adriaens T, Isaac NJB, Kenis M, Onkelinx T, San Martin G, Brown PMJ, Hautier L, Poland RL, Roy DB, Comont R, Eschen R, Frost R, Zindel R, Van Vlaenderen J, Nedvěd O, Ravn HP, Gregoire J-C, de Biseau J-C, Maes D (2012): Invasive alien predator causes rapid declines of native European ladybirds. Diversity and Distributions 18(7): 717-725. doi: 10.1111/j.1472- 4642.2012.00883.x; Winter M, Schweiger O, Klotz S, Nentwig W, Andriopoulos P, Arianoutsou M, Basnou C, Delipetrou P, Didziulis V, Hejda M, Hulme PE, Lambdon PW, Pergl J, Pysek P, Roy DB, Kuhn I (2009) Plant extinctions and introductions lead to phylogenetic and taxonomic homogenization of the European flora. Proceedings of the National Academy of Science USA 106: 21721-21725.