Published: 20 May 2015 at 16:24
New report shows that only Scotland has stood firm against alien ladybird species
The history of how the harlequin ladybird – an insect described as “the most invasive ladybird on Earth” – has spread so successfully across mainland Britain over the last decade, has been published today in the journal Ecological Entomology.
Ten Years of Invasion is co-authored by Dr Helen Roy of the Centre for Ecology & Hydrology and Dr Peter Brown of Anglia Ruskin University.
The harlequin ladybird (Harmonia axyridis) was first recorded in the South East of England in 2004 and thanks to the public submitting over 30,000 recordings to the UK Ladybird Survey since 2005, scientists have plotted its spread in a northerly and westerly direction across mainland Britain.
The research, which examines the factors for its incredible progress, shows that only Scotland has stood firm against the invasion, thanks to its climate (lower temperatures and higher precipitation than England) and less favourable habitats, such as heathland and moorland.
Originally from Asia, the harlequin has proved particularly successful in urban areas, and almost all Scottish recordings have been in towns or cities.
Human involvement also appears to have been key to their spread. For example, the first harlequin spotted in Scotland (in 2007) was a result of the ladybird being transported in a suitcase; while the first record from the Orkney islands (in 2008) involved the ladybirds being transported with vegetables from mainland Britain. Such inadvertent human assistance can greatly increase the rate at which invasive species expand their ranges.
The harlequin outcompetes and directly feeds on other ladybirds, and appears to have played a large part in the decline of species. Since its arrival in 2004, seven out of eight native ladybird species tested have seen a decline in numbers across Britain.
The report concludes that although the harlequin is currently less susceptible to attack by native parasitoids and pathogens than Britain’s native ladybirds, within the next 10 years it is possible that natural enemies will begin to adapt.
Dr Peter Brown, Senior Lecturer in Zoology at Anglia Ruskin University, said:
Dr Helen Roy added: